Power Outage in Des Moines, IA

Public and Law enforcement tweets about multiple trees down, including pulling down power lines, mainly on the east side of the Des Moines metro. Time estimated via radar.

A 12 inch diameter tree limb fell on a power line, causing a house fire. Multiple 5 to 6 inch diameter branches down in the area as well. Time estimated by radar.

A trained spotter reported six inch and larger tree limbs down with power outages. Severe winds lasted 30 minutes.

Public report via social media of power lines down. Time estimated via radar.

Public reports of large tree limbs down across the area, some large enough to fold a chain link fence. Thousands were without power, which was restored by 830a. Radar data indicates likely microburst.

Iowa department of transportation reported power lines and trees down along E 14th and Highway 69. Large tree blocking southbound lanes. Time estimated via radar.

Broadcast media relayed report of tree branches and power lines down near 5th Street and Hart Avenue. Time estimated via radar.

The tornado began near Terra Park and ended near Dewey Park in Johnston. Estimated peak wind speed of 95 mph was determined with damage to multiple large trees and power lines. No damage to buildings was noted.

Des Moines Public Safety reported a tree fell on a power line, causing power flashes in south Des Moines.

Dispatch reported that a tree landed on a car, and nearby another tree was down in the street with some power lines down as well.

Public relayed images of tree branches and power lines down. Time estimated from radar.

Public reported several 3 plus inch tree branches broken across the Beaverdale neighborhood. Over 2000 residents without power. This is a delayed report.

Lightning struck a power pole and knocked out power to the area.

NWS employee reported 4-5 snapped power poles along frontage road west of Merle Hay between Meredith and the Chapel Hill Gardens Cemetery. At least 2 snapped 1/3 to 1/2 up the pole, may have been more snapped, but uncertain.

NWS employee reported tree branches down on Beaver Dr and power outages in Johnston.

Emergency manager reported multiple trees and power lines down in West Des Moines along Ashworth Rd.

Emergency manager stated dozens of reports of power lines down, trees down, power outages from transformer damage, and motor vehicle crashes all suspected to be storm related. Metro wide reports too numerous to report.

Fire department reported 6 to 8 inch tree limb down on a powerline at SW 1st and Davis Ave. Time radar estimated.

Trained spotter reported an approximately 40ft power pole/line snapped in half and downed onto the roadway.

Significant tree and power line damage. Trees down on buildings.

Six power poles snapped with power lines on the road just west of the intersection of Highway 141 and Highway 44.

A tree was blown down onto a power line.

Power lines were down with four to five inches of running water in the streets.

Numerous 10 to 12 inch diameter trees snapped, largest downed were 3 feet in diameter. Trees laying in different directions. Power lines down across the area and the Amateur Radio repeater town was down.

Emergency manager reported tire-deep water flowing down the road at the intersection of 86th and I-80. Power loss and several vehicles stalled.

Telephone pole snapped near the top. Power in the area reportedly out.

Seven power poles were blown down near the intersection of northwest 26th Street and northwest 110th by high winds.

Power poles down.

Several power poles were blown down.

Power poles were downed due to high winds in the Bondurant area.

Multiple power lines were reported downed at multiple locations and reported to be arcing.

A tornado took down power lines and power poles were snapped at 13th Street and Mulberry. The public reported a flipped car at SW 6th Street and Mulberry.

By the evening of August 7th a cool front had sagged into central Iowa with rejuvenated convective development. The continued heat put a damper on most severe development, however high DCAPE and strong cold pools did allow for gusty winds and subsequent tree and power line damage in Des Moines, likely the result of a microburst.

A derecho swept across South Dakota and into Iowa on the evening of July 5th. This resulted in a swath of wind gust from 50 to 65 plus mph resulting in a number of power outages, tree damage, and a few damaged structures. A brief tornado occurred near Estherville with minor damage. As the bowing thunderstorm complex reach central Iowa the gusts had dropped below severe criteria given the less favorable environment with decreased deep layer shear.

Basic Summary: A cluster of storms in northeast Nebraska and southeast South Dakota developed into the destructive derecho that raced eastward across large portions of Iowa, northern Illinois, southern Wisconsin, northern Indiana, and southern Michigan during the morning and afternoon of August 10th. The strongest winds were experienced in central and east-central Iowa where 100+ mph winds were observed. Some of the strongest winds were in an area from roughly Marshalltown, IA eastward along the Highway 30 corridor to the Mississippi River, where estimated winds exceeded 120+ mph and approached 140 mph. A number of QLCS tornadoes were also experienced within the Highway 30 corridor. One of the most remarkable aspects of the derecho was the duration of severe winds, with many areas experiencing at least periodic, if not persistent, severe level (58+ mph) winds over a roughly 30 minute time frame. As the derecho moved eastward out of Iowa, it continued to expand, but weakened from its peak strength. Winds continued to exceed severe criteria (58+ mph) in Illinois, Wisconsin, Indiana, and Michigan and began to produce additional QLCS tornadoes across northern Illinois before fading out across northern Indiana and southern Michigan.||In the wake of the derecho, damage was substantial in many areas, rural and urban. Many agriculture fields, mainly corn, were flattened within the swaths of strongest winds. Initial estimates suggest at least 850,000 acres of partial or complete crop loss occurred from this event. Within urban and wooded areas extensive tree and structure damage was seen, including complete roof failure in a few instances. At its peak, total estimated customers without power exceeded 1.4 million across the affected states. In total, early estimates on losses (agriculture, infrastructure, private property) have exceeded $7.5 billion across the states affected. ||Environment: Broadly speaking, it was a ripe day for thunderstorms across the affected area with MUCAPE values often exceeding 3500-4000 J/kg by the mid morning hours concurrent with mid-upper level short wave support, and indications that any cold pool development would be strong (difference between cold pool and ambient air) and potentially long lived. For detailed environmental analysis, including soundings, please view the various local NWS office event review pages: NWS Des Moines, NWS Quad Cities, NWS Chicago, NWS Milwaukee, NWS Central Illinois, NWS Northern Indiana, or NWS Indianapolis.||Additional Details: Numerous injuries occurred during the derecho and in the aftermath during cleanup, including 4 direct and indirect deaths of which 3 occurred in Iowa (two in Poweshiek County and one in Linn County) and 1 in Indiana (Fort Wayne).||Disclaimer: The August 10, 2020 derecho resulted in widespread high-end damage across large portions of central and southern Iowa. Given the size and scope of the event and understanding that final damage and loss estimates (agriculture, infrastructure, and private property) will take months to complete, the NWS is not able to estimate the monetary impact at this time. Values may be added as more data becomes from various sources in future months.

A mid-level trough across the northern plains allowed for a region of broad ascent to support scattered convection across the area on the morning of June 26th. This activity remained sub-severe with the exception of a suspected microburst on the south side of the Des Moines metro which resulted in significant tree damage and power outages. As the trough pushed east a surface boundary moved across the state later in the day. While this also remained sub-severe, localized pockets of heavy rain did develop.

A boundary remained fairly stationary across the state with environmental parameters continuing to support storm development. Storms across central Iowa produced some wind damage, downing trees and snapping a power pole. A tornado also occurred, cutting through Johnston, a northern Des Moines suburb. Tornado damage was largely confined to trees and powerlines with no structural damage reported.

An area of thunderstorms moved through central and northern Iowa on the morning of the 19th. Lightning struck the Mason City ASOS causing it to lose power. Lightning also struck a tree in the Des Moines metro area and exploded limbs of the tree onto a nearby house causing some damage.

What started out as a cluster of low level jet induced storms over central Nebraska, turned into a derecho that had severe winds and left a path of wind damage from Nebraska into Illinois and then down into parts of southeast Missouri and western Kentucky and Tennessee. The initial convection initiated shortly after 3 am CDT in north central Nebraska within a very unstable nocturnal environment. MUCAPE values were in excess of 5000 J/kg throughout much of central Nebraska, along with DCAPE in excess of 1200-1500 J/kg, effective shear around 30 to 40 kts, roughly perpendicularly oriented 0-3 km shear vectors to the storm orientation, and supporting composite parameters such as MCS Maintenance and Derecho Composite that pointed towards a potentially long-lived convective complex. ||The environment (thermodynamic, moisture, and wind profiles) roughly remained the same as the complex moved eastward, before taking on a more southeast and eventually southern motion, following a strong CAPE gradient. What transpired in Iowa was an eastward moving complex that took on a more linear orientation throughout the morning and quickly trekked across the southern third of the state through the morning and early afternoon. In its wake was dozens of reports of whole trees down, power lines and poles down, other damage reports, and measured wind gusts in excess of 65-70 mph.

It was a hail- and wind-filled day across large parts of Iowa as two distinct rounds of severe weather affected the state. A remnant QLCS system moved out of the eastern Dakotas and southern Minnesota during the early morning hours, maintaining itself in a relatively ripe environment of 2000+ J/kg of MUCAPE and around 30 to 40 kts of effective shear (though fading through the morning). While the storms were able to maintain their vigor, sub-severe to severe hail was seen through parts of Pocahontas, Humboldt, Wright, and Calhoun Counties before they weakened and eventually subsided entirely. ||Later that afternoon, as the surface boundary entered the state, storms once again fired up across the northern to north central areas of the state. The convective environment across the western half or so of the state was quite ripe with as much as 5000 to 6000 J/kg MUCAPE. Effective shear was lacking, however, with predominantly 35 kts or less existing. Hail CAPE approached 1000 J/kg and DCAPE to around 1400 J/kg respectively, indicating the potential for both severe hail and severe downdrafts even with the lackluster shear profile. Afternoon convection saw initial isolated and multi-cell clusters form with hail as the primary threat evolving into a QLCS with a primary wind threat by the mid-evening hours. In total, in excess of 50 severe hail and wind reports were received, including a 2 inch hail report and numerous reports of tree and power line damage.

General surface high pressure remained in the region, keeping the area hot. With moisture off the from remnants of Alberto and general southerly flow down to the Gulf of Mexico, moisture was fairly plentiful with surface dew points in the mid to upper 60s. Support for sustained severe weather was fairly lackluster, with limited hail CAPE, negligible effective shear, but overall SBCAPE values did exceed 3000 to 4000 J/kg. DCAPE values were relatively high in excess of 1000 to 1200 J/kg, raising concern for strong downdrafts/microbursts. ||Lingering convection from western Kansas the day before slowly worked towards western Iowa in the morning hours as waves ejected from a western upper level trough. Additionally, weak warm air advection aided initial storm initiation across the western half of Iowa ahead of the larger wave moving off the Rockies. Initially, numerous storms were seen by early afternoon with most being sub-severe. Outflows form early storms also proceeded to initiate subsequent storms, eventually congealing briefly into a linear looking structure. Nearly all severe reports received were wind related from microbursts and collapsing storms as well as one landspout near Ames. Power outages occurred with the storms with at over 9,000 customers without power at one time or another between Ames and Des Moines.

Strong northwest winds kicked up behind a cold front that swept through the state. Many sites saw sustained winds around 40 mph or higher, with some sites recording gusts over 55 to 60 mph. Damage was reported in the city of Algona in Kossuth County as the roof was blown off the VFW building. Additionally an RWIS site sustained damage to the observation platform as the tower was bent and toppled. A power pole was snapped in the town of Minburn in Dallas County, also in the county a window was blown out of a home in Adel.

A major winter storm affected the entire state during the evening of 31 January into the evening of the 1 February. The northern and southern branch of the jet stream phased over the central U.S. The southern branch drew tropical moisture north into the system as the northern branch brought down colder air. Low pressure organized over the southwest U.S. and moved into Kansas during the evening of the 31st, then tracked across Missouri and into Indiana on the evening of the 1st. Initially, a frontal boundary extended east-northeast out of the low pressure across Iowa. The precipitation fell as rain initially over much of the state. As colder air moved in from the north and west, the rain changed over to heavy wet snow. An extended period of snowfall of a half inch to an inch per hour occurred. Roads became hazardous with some even impassible. Numerous closures occurred. It was fortunate that the storm occurred on a weekend, which decreased the impact somewhat. During the overnight hours, a band of heavy snow set up across central into east central Iowa. These areas received in excess of a foot of snow. This area was generally from west of Des Moines, through Cedar Rapids, into the Quad Cities area. South of the band the snow amounts were generally in the 8 to 10 inch range as the dry slot from the system slowed snowfall rates. North of the band total snowfall was generally around 8 inches. The heavy consistency of the snow during the evening of the 31st into the early morning of the 1st caused power outages as the snow stuck to tree branches. At the peak of the storm, about 16,700 people were without power. As the storm progressed east, winds increased from the north. Winds of 20 to 35 MPH were common, with some gusts of 45 to 50 MPH observed on the 1st. The snow had become drier at that time and was more easily blown around. Blowing snow caused whiteout conditions at times with considerable drifting of the snow. Some of the heaviest snow fell over the central Iowa area. The NWS office in Johnston recorded 14.2 inches, Madrid in Boone County received 14.1 inches, 13.7 inches was reported in Saylorville and Ankeny in Polk County, with 13 inches in Altoona in Polk County. Cold air overspread the state with morning lows on the 2nd falling to zero to 15 below zero. The storm beginning time actually occurred on the 31st of January, though criteria was not met until the 1st of February. The snow started west of an Algona to Fort Dodge to Creston line by 1500 CST on the 31st, reached a Waterloo to Centerville line by 1900 CST on the 31st, and covered the entire CWA by 2100 CST on the 31st. There was one death from the storm. Police in Cass County reported that a woman died of exposure Sunday evening when attempting to get help after crashing her car. A female age 67 lost control and crashed into a ditch around 1630 CST Sunday near Atlantic. She left her car and tried to walk home. Her body was found about four hours later a few blocks from her car. The wind chill was 9 F below zero at the time and she was reportedly not dressed for the weather.

A very dynamic pattern was in place over the state with a closed low located over southern Canada into the north central U.S. A very strong jet of 85 to 100 kts as present at 250 mb. CAPE by early morning was already 3000 to 4000 J/kg with downdraft CAPE of 1000 to 1400 J/kg. CAPE in the -10 to -30 C layer of the atmosphere was between 1000 and 1400 J/kg. The freezing level was around 14,000 feet with precipitable water values near 2 inches. The LCL remained around 750 meters with 75 J/kg of CAPE in the 0-3 km layer. There was strong shear present, with 60-80 kts of effective shear. A cold front moved into Iowa during the day and moved across the state. This event was similar to the event of 29 June 1998. Thunderstorms formed over northeast Nebraska by sunrise and continued to propagate east into Iowa. The storms intensified as they moved across the state, into a forward moving MCS. As it strengthened into a Derecho, winds of 70 to 80 MPH were reported over a large swath of the state. All modes of severe weather occurred. Widespread wind damage was reported to trees, power lines, and structures from the high winds. In addition, very large hail occurred. Some of the larger hail included three to four inch diameter hail in Calhoun County near Rockwell City, and three and one half inch diameter hail in Warren County at Sandyville. Several tornadoes were confirmed. Very heavy rainfall occurred with the storms. The rain lead to flooding and flash flooding in many areas of northern and central Iowa. By the end of the month, a presidential disaster declaration had been made for the follow 9 Iowa counties: Adams, Clarke, Decatur, Mills, Montgomery, Pottawattamie, Ringgold, Taylor and Wayne. Governor Branstad also requested a disaster declaration for the following 26 Iowa Counties: Allamakee, Buchanan, Buena Vista, Butler, Cherokee, Chickasaw, Clay, Dickinson, Emmet, Fayette, Franklin, Hancock, Humboldt, Ida, Kossuth, Lyon, Osceola, Palo Alto, Plymouth, Pocahontas, Sac, Sioux, Winnebago, Winneshiek, Woodbury, and Wright. The Presidential declaration was granted on 24 July 2014.

A very dynamic weather pattern was in place over over Iowa. A warm front lifted north into the state. Temperatures warmed in the 80s with dew point readings in the upper 60s to mid 70s. The atmosphere became very unstable with 3000 to 4000 J/kg of CAPE and downdraft CAPE of 1000 to 1500 J/kg. The shear was strong with 50 to 60 kts available. The freezing level was quite high, between 13,000 and 14,000 feet wtih CAPE in the -10 to -30 C layer of the atmosphere between 700 and 900 J/kg. The precipitable water value was a between 1.5 and 1.8 inches. The LCL was relatively low, around 1000 meters. Thunderstorms moved into western Iowa out of Nebraska. As the afternoon and evening progressed, the thunderstorm complex evolved into one that was more outflow dominated. The system raced southeast and produced high winds across the Des Moines metro area and to the east and south. Winds of 60 to 80 MPH caused considerable tree and power line damage. Power outages were reported by 27,000 customers in Des Moines at the height of the storm. As the storms moved through the heart of Des Moines, a homeless individual died when a large tree branch fell on him at a homeless settlement along the banks of the Raccoon River east of Fluer Blvd.

A strong push of cold air moved into the central US during the afternoon of the 5th through the early morning of the 7th. Arctic air spilled south. Temperatures were not all that atypical for January, though the last time it has been this cold was in January of 2010. Winds of 25 to 45 MPH produced bitterly cold wind chills of 40 to 50 below zero over the north half of Iowa, with 35 to 40 degree below zero readings over the south. The winds caused spotty power outages around the state. An initial wave of outages affected the metro Des Moines area in the late afternoon and early evening The first outage reported about 5,000 out -- 2,000 customers out in Johnston, about 1,000 in Grimes and more than 1,500 out in Urbandale. A second outage impacted 7,400 customers with 3,000 in Johnston and 3,500 in Urbandale about 2100 CST. By 2200 CST, all but 900 in Urbandale had been restored.

A cold front moved into northwest Iowa during the day on the 19th. The front reached southeast Iowa after midnight. The atmosphere was unstable ahead of the front with temperatures warming into the mid 80s to around 90, and surface dewpoint readings in the upper 60s to low 70s. CAPE increased to over 2000 J/kg. Downdraft CAPE was in excess of 1000 J/kg. The freezing level was quite high, around 15,000 feet. Available CAPE in the -10 to -30 C layer of the atmosphere was in the 500 to 800 J/kg range. Precipitable water was around 1.8 inches. Adequate shear was available with the effective shear in the 35 to 45 kt range. A line of thunderstorms developed ahead of the cold front. The storms became severe by the mid afternoon hours. The severe period lasted for about 2 1/2 hours in the Des Moines CWA with the most of the severe weather in a band extending from south of Waterloo, through Des Moines, into the southwest corner of the state. The predominant mode of severe weather was in the form of high winds. Numerous reports of high winds were received with wind speeds of 60 to 80 MPH. In the Des Moines metropolitan area, 40,000 customers were reportedly out of power at the peak of the storm. After 12 hours, nearly one quarter of those still remained without power. Tree and power line damage was widespread along the line. Scattered roof damage was reported in the Des Moines metropolitan area as well. A semi truck was blown over on Highway 169 north of Tingley in Ringgold County. Spotty hail was reported, mainly in Dallas, Polk, and Marion Counties. The largest hail was in Marion County with a report of golf ball size hail in Pleasantville.

A cold front moved into Iowa during the afternoon from the northwest. The airmass became very unstable ahead of the front. Temperatures rose into the upper 80s to low 90s, with dewpoint readings in the upper 60s to lower 70s. CAPE increased to 4000 J/kg by late afternoon with a lifted index between -10 and -18 C. Downdraft CAPE was between 1200 and 1700 J/kg, with CAPE in the -10 to -30 C layer of the atmosphere in the 700 to 900 J/kg range. The freezing level was very high, around 15,000 feet, with the LCL at 1250 meters. Deep moisture was available for the system, with precipitable water values around 1.6 inches. Little shear was available with only 20 kts of effective shear. A line of thunderstorms formed along the cold front during the afternoon and tracked southeast into Iowa. Several of the storms produced hail from the size of quarters to the size of golf balls. Funnel clouds were also reported with a few of the storms. As the thunderstorms continued into the later afternoon and evening, wind became a more dominant factor. Numerous trees were downed by high winds in Wright and Franklin Counties. The storms developed southwest with a line of significant thunderstorms extending from northeast into central Iowa by early to mid evening as new storms formed on the outflow boundary of the original development. The storms continued to produce quarter to golf ball size hail and wind gusts of 60 to 70 MPH. The winds caused spotty building damage, including a barn near Story City. Six horses that were inside were killed. The barn was east of Boone, where buildings and power lines were destroyed at the Central Iowa Expo grounds. Two inch diameter hail was reported in parts of Wright and Boone Counties. A heat burst produced 73 MPH winds in Marion County at the Knoxville Airport. The temperature rose from 70 to 84 in 15 minutes, and the dewpoint dropped from 63 to 48 in 10 minutes.

A warm front moved slowly north into Iowa during the overnight hours of the 28th into the 29th. The airmass became unstable as surface temperatures warmed into the low 80s, with dewpoints around 70 along and south of the front. CAPE rose to around 3000 J/kg with a downdraft CAPE of 900 J/kg, and CAPE in the -10 to -30 C layer of the atmosphere of 600 to 800 J/kg. The lifted index fell to -9 C. Considerable moisture was available with the precipitable water values around 1.7 inches. The atmosphere was moderately sheared with 35 to 40 kts of shear available. Thunderstorms developed rapidly around mid day and produced very heavy rainfall, as well as high winds and hail. Most of the hail was somewhat limited in spite of the relatively low freezing level of 12,600 feet. The LC was relatively low at 1000 meters, however there were no reports of tornadoes. Wind and heavy rainfall was the dominant weather type. Hail was limited to penny size up to 1.5 inches in diameter. Several of the storms produced 60 to 70 MPH winds, downing numerous trees and power lines. The most extensive damage was in Butler County. Winds estimated around 80 MPH caused considerable damage to a containment build and significant structural damage to 18 houses in the town of Greene. Damage in town was around $500,000. A band of 2 to 4 inches of rainfall was observed from southwest through central into northeast Iowa. This caused flash flooding as the rain fell on already saturated soil. There were numerous roads under water from the flood waters. In the Waterloo area, the water was deep enough to submerge cars and cause many motorists to stall out and become stranded buy the flood waters. In the Hudson areas of Black Hawk County, flooding in town occurred as the levy partially failed on the river. Officials in Tama County reported that a bridge was washed out, at a cost of $75,000, and at least $150,000 in damage to secondary roads. In Grundy County, initial estimates of damage to county secondary roads was at least $170,000. As of the 29th of May, Governor Terry Branstad declared 15 Iowa counties disaster areas due to the storms and flooding. They included Buena Vista, Cherokee, Butler, Floyd, Grundy, Johnson, Iowa, Jasper, Marshall, Mitchell, Plymouth, Poweshiek, Sioux, Tama, Wapello, and Wright.

The system that affected the state the previous day continued to affect Iowa as a large upper level low pressure system intensified to the south of the state. Initially, cold air settled into the state during the evening of the 2nd. As the upper low moved east, warm air advection began to take place from south central into central and parts of north central Iowa along a north to south baroclinic zone. A band of heavy snow developed overnight on the 2nd into into the morning of the 3rd. Snowfall rates of an inch or more per hour occurred during the height of the snow. Roads became slick and slushy. Accidents were numerous with a similar situation to what occurred the previous morning. Tree and power line damage occurred as the heavy wet snow brought tree branches and some trees down. Significant tree damage was reported in Marion County due the heavy, wet snow. Some of the heavier snowfall from the event included 12 inches in Chariton in Lucas County, 10 inches in Humeston and south of Allerton in Wayne County, and 10 inches in State Center in Marshall County. In all of these areas, some of the snowfall total occurred the previous day.

A very strong frontal boundary was in place across Iowa during the afternoon of the 9th. Temperatures were in the mid 20s over the far northwest corner of the state, with low 80s in the southeast. Dewpoints reached the mid 50s to low 60s over the southeast as well. Moisture continued to stream into the state on a 30 to 40 MPH low level jet. Precipitable water values increased to between 1 and 1.3 inches. CAPE was around 1000 J/kg across the area with an effective shear of 45 to 55 kts. There was little DCAPE available, however the CAPE in the -10 to -30 C layer of the atmosphere was around 300 J/kg. Thunderstorms formed deep in the cold air from west central through north central into parts of northeast Iowa. The storms produced hail, sufficient to cover the ground in many instances, and scattered high wind events. Nearly all of the storms produced at least small hail with the stronger storms producing severe to significant hail. The largest hail reported was in Crawford County, where 2 inch diameter hail fell south of Charter Oak. Storms produced high winds in the northwest, with damage reported in Pocahontas and Kossuth Counties. A shed was blown over by thunderstorm winds in Pocahontas County at Laurens. Power lines were blown down in Kossuth County at Fenton, while a barn and outbuilding was toppled east of Whittemore.

Part 2 of 2: The seasons first major winter storm moved into Iowa during the late afternoon and evening of the 19th and continued into the day on the 20th and became a blizzard for much of the Des Moines CWA. A strong low pressure developed over southeast Colorado and pushed east across southern Kansas. The low turned northeast through Missouri and into southern Lake Michigan by the 20th. As the low moved into Lower Michigan the pressure fell to 982 mb. This combined with high pressure building into Iowa from the northwest resulting in a very strong pressure gradient across the state. The strong upper level trough of low pressure became negatively tilted as it lifted northeast across the central US, aiding in the low pressure intensification. A strong push of moisture took place ahead of the storm. A mixture of rain and snow developed north and northwest of the low pressure track. As the dry slot lifted northeast toward Iowa, the airmass became increasingly unstable. A large area, for December, of thunderstorms developed over northeast Kansas into northwest Missouri, then pushed rapidly across Iowa during the evening of the 19th. A mixture of rain and snow occurred across southern Iowa during the early evening. The rain/snow line shifted southeast with much of the thunderstorm activity occurring as thundersnow. The thunderstorms brought with them a mixture of snow and some freezing rain. Though the freezing rain was not of a significant amount, it did help to cake the snow that was falling at a one to two inch per hour rate onto trees and power lines. The snow spread north quickly through the evening and early morning hours. The heaviest snow fell in a band about 50 miles wide that extended from near the Omaha-Council Bluffs area, through Des Moines and Waterloo, and eventually all the way to Marquette. Snowfall of 8-12 inches was common in this band with some amounts over 14 inches. Outside of the heavier band of snowfall, 2 to 5 inches of snow was reported. Roads became treacherous quickly with the heavy snow falling on road surface temperatures that were just above freezing. Numerous traffic accidents and injuries were reported, along with some fatalities. The largest accident occurred on Interstate 30 near the Williams exit. The location was near mile marker 150. Thirty cars were involved with two fatalities reported. There were two deaths that occurred in the pile up. A 27 year old female, pregnant with twins, was outside of her car looking for her young son when she was struck and killed. A 43 year old female was killed in her stopped vehicle when another car struck hers. There waere also seven others injured in the pileup. Blowing snow became a major issue as the night progressed. Blizzard and near whiteout conditions were widespread by sunrise across the state. Roads drifted shut in many areas with numerous road closings. Interstate 35 was closed from Ames to the Minnesota line much of the day on the 20th until mid-day on the 21st. Conditions became bad enough that most activities in the state were cancelled for both the 20th and 21st. The strong winds caused snow drifts 5 to 10 feet high in many areas. Blizzard conditions were reported over most of the Des Moines CWA. Sustained winds of 25 to 35 MPH were common across the CWA, with frequent gusts of 45 to 55 MPH. Some of the highest winds included 43 MPH gusting to 57 MPH at Ottumwa at the peak of the storm. Their peak gust was 60 MPH. Other locations at the peak of the storm include Mason City with 36 MPH gusting to 48 MPH, Knoxville 38 MPH gusting to 50 MPH, Marshalltown 36 MPH gusting to 49 MPH, Newton 36 MPH gusting to 53 MPH, Oskaloosa 43 MPH gusting to 54 MPH, Waterloo 39 MPH gusting to 52 MPH, Des Moines 32 MPH gusting to 54 MPH, Ames 35 MPH gusting to 50 MPH, Carroll 39 MPH gusting to 46 MPH, Chariton 28 MPH gusting to 49 MPH, Lamoni 35 MPH gusting to 50 MPH, and Grinnell 39 MPH gusting to 50 MPH.

Part 1 of 2: The seasons first major winter storm moved into Iowa during the late afternoon and evening of the 19th and continued into the day on the 20th. A strong low pressure developed over southeast Colorado and pushed east across southern Kansas. The low turned northeast through Missouri and into southern Lake Michigan by the 20th. At the same time, a strong upper level trough of low pressure became negatively tilted as it lifted northeast across the central U.S. A strong push of moisture took place ahead of the storm. A mixture of rain and snow developed north and northwest of the low pressure track. As the dry slot lifted northeast toward Iowa, the airmass became increasingly unstable. A large area, for December, of thunderstorms developed over northeast Kansas into northwest Missouri, then pushed rapidly across Iowa during the evening of the 19th. A mixture of rain and snow occurred across southern Iowa during the early evening. The rain/snow line shifted southeast with much of the thunderstorm activity occurring as thundersnow. The thunderstorms brought with them a mixture of snow and some freezing rain. Though the freezing rain was not of a significant amount, it did help to cake the snow that was falling at a one to two inch per hour rate onto trees and power lines. The snow spread north quickly through the evening and early morning hours. The heaviest snow fell in a band about 50 miles wide that extended from near the Omaha-Council Bluffs area, through Des Moines and Waterloo, and all the way to Marquette. Snowfall of 8-12 inches was common in this band. Some of the heavier snowfall amounts included 14.5 inches in Ankeny, 13.8 inches in Johnston, 13.4 inches in Grimes, 13 inches in Conrad and Marshalltown, 12.4 inches at the Des Moines Airport and 11.5 inches south of Madrid. Roads became treacherous quickly with the heavy snow falling on road surface temperatures that were just above freezing. Numerous traffic accidents and injuries were reported, along with some fatalities. The largest accident occurred on Interstate 30 near the Williams exit. Thirty cars were involved with two fatalities reported. Icing on trees and power lines became a major issue, especially as winds increased later in the night. Snow and ice laden trees and power lines produced considerable damage through much of the area. Branches and full trees fell on power lines, knocking out power for 150,000 to 200,000 customers, 139,000 in the MidAmerican Service area alone. Conditions became bad enough that most activities in the state were cancelled for both the 20th and 21st. In addition to the snow, strong winds caused considerable blowing and drifting of snow. Snowdrifts of 5 to 10 feet were common. Winds were sustained above 25 MPH across the area, with much of the state reaching frequent gusts of 50 MPH or more. Blizzard conditions were reported over most of the Des Moines CWA. This will be addressed via a separate entry.

Strong heating took place during the afternoon of the 4th. Temperatures warmed into the 90s across the state with dewpoint readings in the mid 60s to low 70s. CAPE increased to 3000 to 4000 J/kg by evening with the lifted index falling to -8 to -12 C. Downdraft CAPE was in the 1500 to 1800 J/kg range. The shear was decent with 30 to 50 kts of effective shear available. CAPE in the -10 to -30 C layer of the atmosphere was 800 to 1100 J/kg. The freezing level was quite high at 14,500 feet with precipitable water of 1.2 to 1.6 inches. The LCL was very high, in the 1500 to 2000 meter range. Strong dynamics were in place with a 90 kt jet to the north of the area. A cold front moved toward the state as low pressure was located over northeast Nebraska with a weak frontal boundary extending east from the low. Thunderstorms formed over eastern South Dakota into extreme northeast Nebraska and advanced rapidly east across northern Iowa. As the event progressed, part of the line took on a bow echo appearance as it pushed across northern Iowa. South of the line a strong outflow boundary pushed south through central Iowa. The bow echo produced high winds of 60 to 75 MPH as it plowed across the north. Numerous reports of tree and power line damage were received. Winds in the Mason City area topped out around 70 MPH, with winds farther south in Hamilton County approached 75 MPH. There were few reports of hail with the storms. Penny size hail was reported in the metro Des Moines area of Polk County. This was the largest hail report received.

A cold front pushed into northwest Iowa during the afternoon of the 8th. Temperatures warmed in to the upper 80s to low 90s, with dewpoint readings in the mid to upper 60s during the afternoon. CAPE rose to 2000 to 2500 J/kg, though the atmosphere was weakly sheared with 25 kts of shear available. Downdraft CAPE was significant with around 1000 J/kg available. The lifted index fell to between -6 to -9 C as moisture increased. By late afternoon the precipitable water value was around 1.6 inches. The freezing level was around 13,500 feet, which was not conducive to hail given the weakly sheared environment. CAPE in the -10 to -30 C layer of the atmosphere was in the 500 to 700 J/kg range. An area of thunderstorms formed over western Iowa and advanced east across the state. An area from west central into central Iowa intensified. Hail up to half dollar size was reported at several locations. Part of the line began to bow out and was able to take advantage of the DCAPE. Winds of 60 to 70 MPH moved through central Iowa, including the Des Moines metro area. Winds near 75 MPH swept into the west side of the Des Moines Metro area. The winds lasted from 10 to 20 minutes. Hail falling at the time caused damage to houses as the hail was driven through the siding of some of them. There were numerous reports of trees down and power outages. At one point 7,000 to 10,000 customers were out of service. Heavy rainfall of nearly 2 inches in under an hour was reported around Des Moines. The heavy rain caused significant street flooding and caused many motorists to stall out. Thunderstorms formed over northern Iowa during the late afternoon in response to an upper level system. The storms produced wind gusts as high 66 MPH in the Mason City area. Quarter size hail was reported from one of the stronger cells in Franklin County.

A very hot airmass was in place over Iowa, though it was capped through the daytime hours. High temperatures reached the mid to upper 90s in the north and 100 to 108 across the south. A cold front moved into northwest Iowa during the afternoon. Dewpoint temperatures pooled along the front to the 65 to 70 degree range. The atmosphere became unstable with the lifted index falling to around -5 C and CAPE increasing to between 2000 and 4000 J/kg. CAPE in the -10 to -30 C layer of the atmosphere was between 400 and 700 J/kg, but the freezing level was around 15,000 feet and shear 20 kts or less. Precipitable water values were high at around 2 inches. The primary mode of severe weather was high winds. A line of thunderstorms formed along the cold front during the early evening hours, rapid intensification once they broke through the cap. The storms became cold pool dominated by mid evening with the outflow boundary leading the storms by about 30 miles. Most of the storms produced winds of 50 to 60 MPH, with a few gusts of 65 to 75 MPH. The highest winds were in Carroll and Poweshiek Counties. Downdraft CAPE was between 1200 and 1800 J/kg. There was little tornado threat with the LCL between 2500 and 3500 meters. There were a few reports of hail, but most of the hail was under an inch in diameter and not a primary event. One report of golf ball size hail was received from the Ruthven area in Palo Alto County. Winds caused numerous power outages and also damaged many trees. As a storm moved through Boone County, the Central Iowa Expo building was flattened. It was under construction with three sides of the building completed. High winds at the Ames Airport flipped a plane over from the same storm that moved through Boone County.

A strong upper level system moved through the central U.S. during the day on the 10th. A cold front entered northwest Iowa during the afternoon of the 10th, and continued across the state during the night. The airmass became unstable ahead of the front with afternoon highs reaching the low 90s with dewpoints in the low to mid 60s in a narrow band ahead of the cold front. The atmosphere was weakly sheared with about 35 kts of shear available. Lifted indices fell to the -4 to -6 C range with CAPE of 1000 to 2000 J/kg. CAPE in the -10 to -30 C layer of the atmosphere was 400 to 500 J/kg, but hail production was limited by a high freezing level of around 15,000 feet. Downdraft CAPE was quite high, in the 1000 to 1300 J/kg range. Precipitable water values increased to 1.7 inches along the front, but rainfall was limited by the fact that the convection was relatively weak given other parameters. Many of the storms produced 40 to 50 MPH winds. A few produced severe winds. One storm in Emmet County toppled a two foot diameter tree and damaged a garage. Another in Cass County topped trees onto power lines on Olive Street south of Interstate 80. As the thunderstorms moved through the Bondurant area, lightning struck a house, setting it on fire.

The first significant severe weather outbreak of the season took place during the afternoon and evening of the 14th with all modes of severe weather taking place. An upper level low pressure lifted northeast out of the southwest U.S. The upper level center, as well as the surface low, passed northwest of Iowa, across southeast South Dakota into Minnesota. Severe weather developed north of the warm front as it lifted north into Iowa. A cluster of severe storms formed over northeast Kansas and southeast Nebraska. These storms moved east-northeast along the warm front into Iowa, causing a considerable amount of severe weather. Severe weather parameters were fairly strong, however the dynamics of a 100 kt mid level jet and 60 kt low level jet made up the difference. Just prior to the storm development, CAPE values were around 4000 J/kg south of the development. Helicity was high, in the 300 to 500 range. There was a large amount of effective shear with 50 to 65 kts available. CAPE in the -10 to -30 layer of the atmosphere was in the 200 to 400 J/kg range, while downdraft CAPE was 600 to 800 J/kg. Plenty of low level moisture was drawn into the state on the strong low level jet. Precipitable water vales rose to 1.25 inches quite rapidly. The LCL level was relatively high, but given the dynmics was relatively easy to overcome. The LCL was just under 1000 meters at the beginning of the event. There were three tornadoes reported during the event. One was northwest of the Creston area in Union County. The most significant tornado caused high end EF2 damage to the far northwest corner of Creston. This tornado formed southwest of Cromwell at 1752 CST in Adams county and quickly tracked into northwest Creston around 1800 CST. EF2 damage occurred to the Greater Regional Medical Center and the Southwestern Community College campus. The tornado continued tracking to the northeast and damaged several farmsteads northeast of Creston before dissipating about 10 miles northeast of town at approximately 1815 CST. The wind strength was estimated to be 130 MPH. Significant damage occurred with uninsured damage alone near $2,000,000. A tornado touched down in Warren County east of New Virginia. The tornado caused damage to farm buildings and campers with a considerable amount of sheet metal left lying around. The EF1 tornado produced winds around 100 MPH. Many of the thunderstorms brought with them high winds and hail. The final tornado touched down in Mahaska County. The tornado was an EF1 tornado with a broad and intense rear flank downdraft south of the track. The AWOS site at the Oskaloosa airport in Mahaska County recorded a 97 MPH wind gust from the rear flank downdraft of the storm. Reports from the Emergency Manager indicated that damage at the airport was limited to two hangar doors and some damage to airport buildings. There were no planes on the field at the time. Numerous reports of hail larger than quarter size were received. Some of the larger hail included baseball size hail in Clarke County at Murray and numerous reports of golf ball size hail along the track of the severe cluster from Union County to Mahaska County. The same cluster of storms also produced very strong winds along its path. Numerous reports of 60 to 70 MPH winds were received all along the path. Numerous reports of tree and power line damage were received. The Des Moines metro area was hard hit with winds of up to 65 MPH causing considerable tree damage. At one time, 20,000 customers were reported without power. In Marion County a garage was destroyed and a house significantly damaged by the wind east of Knoxville. The storms also produced very heavy rainfall. Rainfall of 2 to 4 inches was reported at several locations. At the Des Moines International Airport, 1.10 inches of rain fell between 1630 and 1637 CST. This amount of rainfall in that short of period of time was a 100 year event. Fortunately it had been quite dry across the state, limiting the flash flood potential. Flash flooding was reported in Polk, Cass, and Madison Counties. Water was reported flowing one to two feet deep. Numerous reports were also received of street flooding and significant ponding.

A very strong upper level trough of low pressure was in place to the west of Iowa. Unseasonably warm and moist air pushed north into the state. Record high temperatures occurred for several days, and on the 19th continued over the central and eastern part of the state. Temperatures warmed into the low 80s with dewpoint readings in the low 60s. The atmosphere became unstable with lifted indices around -3 C and most unstable CAPE values in the 1000 to 2000 J/kg range. The wind profile was fairly unidirectional, however speeds in the 850 to 500 mb level were in the 45 to 65 kt range. Downdraft CAPE was around 600 J/kg. Though the freezing level was quite low for a severe weather event, around 11,200 feet, CAPE in the -10 to -30 C layer of the atmosphere was limited to around 100 J/kg. Combined with very high precipitable water values, around 1.4 inches, the hail production was limited. There was a decent amount of shear available for the storms with a shear value around 40 kts. A line of thunderstorms formed ahead of a slow moving cold front that advanced east with the upper trough. Small segmented lines formed that extended east-southeast out of the main north to south line. These segments lifted rapidly north with the mean flow. As a result, it was quite easy for the storms to produce high winds. Winds near 60 MPH caused tree and power pole damage west of the Des Moines Airport with one of the storms. One of the storms produced a small microburst and winds estimated of at least 75 MPH just west of the Des Moines Airport. The high winds downed several large trees. A small line segment produced 60 to 65 MPH winds as it moved through Hamilton County, north through the Mason City area in Cerro Gordo County.

An intense low pressure area moved from northeast Nebraska, across southern Minnesota, into southern Wisconsin during the night of the 28th through the day on the 29th. The dry low pushed over Iowa during the night and produced gusty southwest winds. During the day, a tropospheric fold developed with the fold reaching down to 540 mb. This helped to enhance wind speeds across the state. High winds begin around sunrise with wind gusts of 69 MPH in the Rockwell City area of Calhoun County by 0740 CST. In Carroll County, the Carroll Mesonet site recorded a 61 MPH wind gust by 0618 CST. Other strong gusts included a 67 MPH wind gust in Dawson, a 61 MPH wind gust in Webster County, and a 60 MPH wind gust near Webster City in Hamilton County. The winds in Hamilton County were accompanied by 2 inches of snow and a brief visibility restriction to about 500 feet. Spotty reports of winds of 55 to 60 MPH were also received, such as a 58 MPH wind gust at Fontanelle in Adair County. Sustained winds of 40 to 45 MPH were common across the high wind warning area through much of the morning into the mid afternoon hours. Winds diminished by the mid to late afternoon hours. Spotty reports of damage were received. A canopy of a gas station was blown off in Calhoun County in Manson. In addition, part of the roof of a school in Manson was ripped off. Tree and power line damage was reported in Carroll and Guthrie Counties in the Coon Rapids area.

Low pressure intensified as it moved across Iowa during the evening of the 31st into the morning of the 1st. A strong cold front passed through the state with a very tight pressure gradient behind the low. Strong winds became established in the low levels with winds below 5000 feet AGL in the 40 to 60 kt range. Strong subsidence behind the front allowed the strong winds aloft to mix down. A widespread area of north central into central Iowa reported sustained winds of 40 to 45 MPH with spotty gusts near 60 MPH recorded over the north during the predawn hours. The strongest winds occurred on the bridge over Saylorville Lake in Polk County with a wind gust of 72 MPH. Winds of 59 MPH were reported in Hancock County at Kanawha and in Marshall County at Marshalltown. Some tree damage occurred, along with minor property damage. Spotty power outages were reported around the state as well. There were about 1000 customers out of power in the Des Moines Metro area before dawn on the 1st, with nearly 2500 out of power in the Waterloo Metro area. The winds dropped off toward sunrise, allowing many of the customers out of power to be placed back on line. A shortwave dropped southeast across the area during the day on the 1st, bring another round of high winds. Though winds did not gust to 50 kts with the second round, most locations reported sustained winds of 40 to 45 MPH with gusts to around 55 MPH for several hours through the mid morning and early afternoon. Additional power outages occurred with around 2000 more homes knocked out in the Des Moines Metropolitan area. Overall, damage was limited with the event due to a couple of factors. One was the fact that the event was a low end high wind event, the second being it was January, the tree damage is limited due to the lack of leaves.

A very unstable airmass was in place over Iowa with CAPE values around 6000 J/kg and lifted indices around -11 C. The downdraft CAPE was 1500 to 1900 J/kg. CAPE in the -10 to -30 C layer of the atmosphere was high, in the 800 to 1200 J/kg range, however the freezing level was 15,500 feet, limiting the hail production. The shear profile was relatively weak with 30 kts of effective shear available. Predawn temperatures were in the upper 70s to around 80, with dewpoints in the mid 70s. Precipitable water values were in the 1.5 to 2 inch range, boosted by a 35 kt low level jet. Thunderstorms formed in two complexes along a weak frontal boundary extending from Minnesota into Kansas. One of the complexes pushed north and east out of Kansas and Nebraska, the second was over southern Minnesota. The two filled in during the night as the whole system moved into richer air. An outflow boundary was located across northern Iowa from the complex in Minnesota, enhancing convection there. As the storms moved into Iowa, the primary threat came in the form of wind with wind gusts of 40 to 60 MPH associated with the fast moving forward propagating MCS. Wind damage occurred in the Atlantic area with a tree blocking U.S. Highway 6. This cluster of storms continued to move across the state at around 55 MPH. Wind damage occurred in the Des Moines area with tree branches down and power line damage caused by 60 MPH winds. A 59 MPH wind gust was recorded at the Ames Airport as the storms passed. As the complex of storms continued east out of central Iowa, widespread damage occurred across Marshall and Tama Counties with winds of 70 to 100 MPH. Two radio towers were downed, one in central Tama County, the other in northern Polk County. A local television station's weather radar was destroyed near Alleman, also in Polk County. Local wind speeds in these areas were estimated as high as 115 MPH. Widespread power outages were reported with 90% of the power still out in Marshall County, and 75% out in Tama County 12 hours after the event. Power was out for 3 to 4 days in some places. Governor Terry Brandstad gave a State Disaster Proclamation to Story, Marshall, and Tama Counties due the extensive damage. A presidential declaration for major disaster was also given to Story, Marshall, and Tama Counties. A broad area of severe damage occurred with a path 5 miles wide of EF1 type damage caused by the high winds. A path, 10 miles wide, of 70 to 80 MPH was surveyed, with a 15 to 20 mile wide path of wind speeds above 60 MPH. The damage swath was nearly continuous with no evidence of tornadoes. It extended from southern Story and northern Polk Counties, through Marshall, and Tama Counties, and was about 75 miles in length before exiting the CWA. Crop losses were substantial with around 40% or greater loss on over 100,000 acres of corn and soy beans. The corn had much more damage than the bean plants, with damage on these acres estimated at $95,000,000. Other damage occurred around the area as well. This derecho event was the most widespread one to affect central and east central Iowa since the June 1998 event. Some examples of the notable wind speeds estimated from the survey include 96 MPH near Huxley, 94 MPH near Maxwell, 70 to 90 MPH near Marshalltown, 105 MPH east of Garwin, 85 to 97 MPH between Garwin and Union Grove State Park, 100 MPH south of Traer, and south to southwest of Dysart 105 to 115 MPH, with 80 to 100 MPH winds just south of that part of the swath. One dairy farmer near Dysart reported the total loss of 300 acres of corn and $300,000 damage to the farm. Several of his dairy cows perished or had to be euthanized. The farmer said he would have to go out of the farming business after 45 years due to the extent of the loss. In Tama County, officials reported that 1000 county road signs were destroyed by the high wind. Meanwhile, the northern part of the system continued to produce strong winds with a 63 MPH wind gust reported at the Fort Dodge Airport.

A dynamic pattern was once again in place over the central U.S. A strong surge of moisture took place during the day on the 26th, with precipitable water values rising to over 2 inches by evening. The airmass became very unstable with the lifted index falling to around -8 and CAPE in excess of 4000 J/kg. The atmosphere was quite warm with the freezing level between 15,000 and 16,000 feet. CAPE in the -10 to -30 C layer of the atmosphere was around 600 J/kg. Downdraft CAPE was quite high, in the 1200 to 1500 J/kg range. Considerable shear was available with shear in the 50 to 65 kt range. Meanwhile, a strong mid level trough of low pressure approached the central U.S. along with a moderate cold front approaching from the northwest. During the night, the low level jet increased to 70 kts, further feeding the thunderstorms. A large complex of thunderstorms developed across South Dakota into Nebraska. It moved southeast into the rich air over Iowa and accelerated, becoming a derecho. A large area of high winds developed with widespread wind gusts of 60 to 75 MPH, mainly over the southwest half of the CWA. The storms also produced hail at most locations as it passed. Most of the hail was around an inch or so in diameter. A smaller area of thunderstorms formed over southeast Iowa, ahead of the main area. These storms produced hail up to golf ball in size, along with 60 MPH winds during the early evening. The largest hail reported was 2 inches in diameter in Cincinnati in Appanoose County. The storms produced copious rainfall in spite of their rapid movement. Flash flooding was reported in Union, Adair, Davis, and Adams Counties. For the most part the flash flooding was relatively minor, limited to water flowing rapidly over roads. In Davis County at Bloomfield, water blew off manhole covers and was deep enough to nearly reach the tops of car roofs. The thunderstorm winds caused widespread damage to trees and power lines. A semi-truck was overturned on Highway 141 west of Woodward by the winds. Another was overturned in Carroll County on U.S. highway 30. A high wind event also took place with the storm complex as a wake low formed. Strong easterly winds developed with wind speeds in the 60 to 75 MPH range common. The strongest winds occurred in Webster County at Callendar. Winds of 80 to 90 MPH blew down mailbox posts, blew down trees onto houses, and picked up a swing set and blew it through the window of a house. Tree and power line damage was quite widespread over a 7 county area. One tornado touched down in Carroll County south of Halbur. A narrow swath of damage occurred from about one quarter mile south of the intersection of Granite Ave and County Road E53, with the roof blown off a hog confinement building just southeast of the intersection. Minor damage continued along a path 2.5 miles long to the east with another roof partially blown off of a Morton building just southwest of the intersection of County Road E53 and Ivy Ave. The tornado lifted about one quarter of a mile southeast of the intersection.

A strong warm front was located to the south of Iowa as a very strong push of warm and moist air was driven north into the area by a 60 kt low level jet. The airmass was very unstable with CAPE greater than 5000 J/kg with lifted indices near -10 just to the south of the front. The airmass was relatively capped with 700 mb temperatures around +15 C. Precipitable water values increased to near 2 inches. Convection developed rapidly over southwest Iowa during the late evening The activity became severe quickly, producing hail of quarter to ping pong ball in size. Intense rainfall also occurred with the storms with rainfall of one to three inches per hour reported. As the storm system evolved, the storms began to turn into wind producing storms over southern Iowa. Winds of around 60 MPH blew across the southern two tiers of counties, causing damage to trees, power lines, and some minor damage to outbuildings in the area. One of the stronger storms blew the awning off of a camper and ripped siding from part of a house northeast of Russell in Lucas County. As the night progressed, thunderstorms continued to develop and wind became more of an issue. High winds also caused damage in Cass County at Atlantic. Numerous locations reported winds of 50 MPH with the storms as well. One tornado touched down in Mahaska County near New Sharon. It was a small tornado with damage embedded in a narrow path of straight line wind damage. Most of the damage was to trees and occurred on the south side of New Sharon and 2 miles to the west and east. The tornado destroyed one quarter of a rental building and carried it up to one quarter of a miles across a cemetery and part of the high school track. At least 40 gravestones were toppled by the wind and carried debris.

A strong MCS moved southeast out of South Dakota into Iowa during the morning of the 13th. The system was elevated in nature and swept southeast along the edge of the unstable airmass to the southwest. Wind shear was fairly strong, 50 to 60 kts, helping to maintain the system. Downdraft CAPE was over 1000 J/kg ahead of the storms, but being elevated the storms were only able to make partial use of the high CAPE. As the storms rolled southeast across the state, they produced heavy rain and gusty winds. A few gusts to around 60 MPH were recorded, but they were spotty. Hail from the storms was under an inch in diameter. The storms produced upwards of 2 inches of rain in a short period of time in some places as well. The more significant part of this event was the formation of a strong wake low. Strong winds developed in the wake of the storms with sustained winds around 40 MPH, and gusts of 60 to nearly 70 MPH reported across 7 counties of central Iowa. The winds downed trees and power lines and also caused damage to some outbuildings. A three foot diameter tree was blown down on an house in Nevada in Story County. The strongest measured wind speed was received from a mesonet site in Colo with a 68 MPH wind gust. Tree damage was widespread over southern Story County from Slater to Nevada. As the storms moved through Guthrie County, lightning struck a house in Panora. It blew a whole through the roof and started the insulation on fire, resulting in minor damage. Lightning also struck a tree next to a house in Stuart. The tree was damaged with pieces of the tree falling onto and damaging a car.

Another round of severe weather and heavy rain took place during the late afternoon and evening hours of the 9th, lasting into the early morning of the 10th. A strong shortwave lifted northeast across the area. This resulted in considerable overrunning of the stalled cold front to the south of Iowa. CAPE was in the 2000+ J/kg range with lifted indices around -11 to the south of the front. CAPE in the -10 to -30 C layer of the atmosphere remained in the 500 to 1000 J/kg range, though freezing levels approached 14,000 feet. Downdraft CAPE was significant, around 1000 J/kg, however a relatively deep layer of cool air was in place over Iowa which limited the high wind potential. The shear in the atmosphere was fairly strong, around 50 kts. Thunderstorms fired up over southern Iowa to the north of the warm front, while another large area formed over western Iowa and moved east. The primary mode of severe weather was in the form of hail from nickel size to golf ball size. High winds occurred with a few of the storms, downing trees and power lines in a few places. The other significant weather event was the very heavy rainfall. Daily rainfall totals of 3 to nearly 5.5 inches were common over parts of central into south central Iowa. The Des Moines airport recorded 4.53 inches of rain by midnight to set a daily rainfall record. Another third of an inch fell after that by 300 AM. In Warren County at St. Marys, 5.4 inches was recorded, with 5.21 inches in Marion County at Swan. Polk City in Polk County received 5.01 inches, with 4.61 in Windsor Heights by midnight. Northeast of Patterson in Warren County reported a 24 hour rainfall total of 6.7 inches, with a total for the storm approaching 10 inches. There were numerous other reports of 4 to 6 inches of rain in Warren and Marion Counties. The heaviest two day rainfall total was 9.31 inches, with 6.78 falling between the morning of the 9th and morning of the 10th. Flash flooding occurred in Polk, Marion, and Warren Counties. Local rivers and streams overflowed their banks with reports of 8 to 10 inches of rapidly flowing water in the streets. On the east side of Des Moines, four feet of water flooded streets. Once the flash flooding subsided, areal flooding was a significant problem in Warren, Marion, and Mahaska Counties. Numerous roads were flooded and closed with countless homes flooded.

A strong surge of moisture and warm air took place during the overnight hours of the 28th into the morning of the 29th. The low level jet was around 50 kts during the predawn hours. Precipitable water values increased to 1.5 to 1.7 inches during the early morning hours. The airmass became very unstable with CAPE values increasing to near 4000 J/kg just south of Iowa, with lifted indices around -8 C. The atmosphere had a fair amount of shear with 50 to 55 kts available. Downdraft CAPE was in the 500 to 800 J/kg range, with 300 to 600 J/kg of CAPE in the -10 to -30 C layer of the atmosphere. During the night, the freezing level increased from under 13,000 feet at sunset, to between 13,500 and 14,000 feet by sunrise. Thunderstorms initially formed in two areas. One was in a west to east band, ahead of the warm front, south of Iowa. The second was a small MCS that tracked along a mid level boundary in Nebraska. As the night progressed, the storms in Missouri weakened as a new area of strong storms formed as the MCS began to interact with the low level jet. Thunderstorms fired rapidly over southeast Nebraska and southwest Iowa just before sunrise. The storms became severe as they moved across the southern third of Iowa. Initially, the storms produced hail with nickel to ping pong ball size hail reported at several places. As the storms progressed, they formed into a more linear structure and the line began to accelerate. As a result, the storms turned into more of a wind hazard. The high winds blew a semi-tractor trailer off the highway near Knoxville. A 69 MPH wind gust was recorded at the Oskaloosa Airport. In addition, there were numerous reports of trees and power lines being blown down by the strong winds.

Low pressure formed to the west of Iowa and during the morning it was located over central Nebraska with a warm front extending east-southeast across southern Iowa. The low advanced east during the day as the warm front moved little. Initially, the airmass was capped by a strong elevated mixed layer. During the late afternoon and early evening hours, a strong upper level short wave moved into the area. Temperatures aloft fell rapidly, destabilizing the atmosphere. Meanwhile, a strong low level jet formed ahead of the approaching low with winds of 40 to 50 kts. This helped to bring in moisture and increased the precipitable water values to around an inch over much of Iowa. By late afternoon, most unstable CAPE values were in the 1000 to 2000 J/kg range. Surface lifted indices were not all that impressive, however the elevated values were in the -3 to -6 C range. The atmosphere was strongly sheared with 50 to 70 kts of available shear. The LCL values were quite low as strong heating had not taken place during the day. LCL heights were between 500 and 1000 meters. Downdraft CAPE was quite high with values just ahead of the convection between 700 and 1000 J/kg. The freezing level was quite low, near 11,000 feet, and available CAPE in the -10 to -30 C layer of the atmosphere was between 400 and 500 J/kg. Thunderstorms fired along and just south of the surface low along a dry line ahead of the associated cold front. Convection was strong and moved rapidly northeast. There were two areas of thunderstorms. A line of strong to severe thunderstorms formed just ahead of the cold front, with more isolated severe convection forming ahead of the main line. There were numerous reports of tornadoes, mainly with the leading convection. The three strongest tornadoes took place west to northwest of Creston in Union County, and northwest to north of Winterset in Madison County and southeast of Massena in Cass County. The tornado in Cass County touched down approximately 1/2 mile east of the intersection of Iowa Hwy 148 and County Hwy G61. It damaged the canopy to an outdoor storage building and tipped over some industrial machinery. It continued northeast and damaged a structure...and caused some minor additional damage to a farmstead north of the intersection of County Hwy G61 and 760th St. Finally, it damaged some outdoor storage bins south of the intersection of County Hwy G53 and 770th Street. It then lifted. The same parent storm continued northeast and a small EF0 tornado touched down briefly near Bridgewater in Adair County. In Madison County, A tornado touched down 10 miles northwest of Winterset. The tornado was characterized by a large circulation up to 0.8 tenths of a mile wide (Iowa Helicopter) and generally of EF1 (90-100 MPH wind) strength. Eyewitnesses report the tornado was rain wrapped and difficult to distinguish from the rain shield as it approached them from the southwest. The tornado moved across several residences, many of which had broken windows and some roof damage along with significant tree and outbuilding damage. One newly constructed house that was near completion, slid off its foundation with the metal tie down straps either sheered off or pulled out of the concrete foundation. This damage is consistent with winds around 120 MPH which are EF2 strength. The roof structure remained intact and was aided by hurricane clips. Several other residences suffered partial roof removal with no hurricane clips noted. One other location had numerous trees either uprooted or topped and several outbuildings with the roofs blown off. Objects near the ground did not suffer near as much damage suggesting the peak winds at this location were just off the surface. The tornado lifted around 10 miles north northeast of Winterset or 5 miles south of Van Meter around 1735 CST. The tornado in Union County was not as intense, with damage there relatively minor. In addition to the line of severe thunderstorms, there was also convection that developed to the north of the low pressure track. Outside of the tornadic storms, the primary mode of severe weather was hail. There were reports of hail with most of the storms as they passed, with several reports of hail from quarter up to golf ball in size. Hail caused damage to roofs and vehicles. Fortunately, the crops had not been planted so there wasn't any agricultural loss. A few reports of strong winds were received with wind gusts in the 60 to 65 MPH range. Some tree and power line damage occurred, but it was not widespread. Heavy rainfall caused minor flooding in the metropolitan Des Moines area. A rainfall of 1.73 inches in under 2 hours in West Des Moines resulted in minor urban flooding along EP True Parkway. Water was standing 1 to 2 feet deep in low drainage areas along the parkway. There were also numerous reports of urban flooding around the city with water standing in intersections. As the thunderstorms moved through Butler County, lightning struck a barn near Shell Rock. The lightning caused damage to the barn and a minor fire.

A powerful storm system moved into the southwest U.S. on January 31st into the 1st The system moved east-northeast across the southern U.S. on the 1st into early the 2nd. Surface low pressure developed over west Texas. The low tracked across Arkansas and eventually through the Ohio River Valley. A considerable amount of moisture was drawn north into the storm system. A very large shield of precipitation developed to the north of the low pressure track. The main deformation zone was nearly 4 degrees wide, covering a large part of the mid section of the country. Snow spread north into Iowa during the afternoon of the 1st and picked up in intensity rapidly during the late afternoon and early evening hours. The low pressure system deepened rapidly as well. A strong pressure gradient was in place over the state. As the low crossed extreme southern Illinois, the pressure dropped to about 995 mb. At the same time a high pressure of nearly 1050 mb was located over western North Dakota. Winds increased rapidly during the evening with sustained winds of 25 to 35 MPH across most of the state. Winds gusted to around 50 MPH over the southeast half. The combination of falling snow and strong winds dropped visibility to less than 1/4 mile for several hours. Whiteout conditions were reported in many rural areas. Roads became impassible in places, and treacherous everywhere. Several highways were closed, however most of the main highways remained open, including Interstate 80. Numerous businesses and nearly all schools closed by the afternoon of the 1st and remained closed on the 2nd. Snowfall of 6 inches or more occurred over about the southeast half of the state, with accumulations in excess of 8 inches over the southeast third. The heaviest accumulation in the Des Moines CWA was 12.3 inches in the Centerville area of Appanoose County. In Monroe County, 11.9 inches was reported in Albia with 11.4 inches falling around Allerton in Wayne County. In Poweshiek County 10.9 inches of snow was recorded at Grinnell. The heavier snow accumulation over southeast Iowa was in part the result of convection. There were numerous reports of thundersnow from Ottumwa north toward the Grinnell area. This is the same event also listed in Stormdata as the 01 February Winter Storm for southwest into west central Iowa.

The seasons first widespread major storm struck the state on the 11th, and continued into the early morning hours of the 12th. A strong upper level system intensified over the central U.S. from the 10th into the 11th. Surface low pressure developed to the west of Iowa, and moved east into northwest Iowa by the early morning of the 11th. The low continued across the north half of Iowa on the 11th, reaching Lower Michigan by mid day on the 12th. Initially, the storm was quite moisture starved. As it intensified, the dynamics of the storm strengthened the inflow, feeding the storm system. The presentation on satellite imagery was classic by the morning of the 11th with a clear dry slot and deformation zone present. The dry slot punched into southwest and central Iowa with a line of showers and isolated thunderstorms firing up on the leading edge of the dry slot. Cold air rushed in on the back side of the storm. The deformation zone curled around the back side of the low and produced moderate to occasionally heavy snow. Temperatures plummeted as strong northwest winds swept across the state. Blizzard conditions developed as winds increased to sustained winds of 30 to 45 MPH, with gusts to near 70 MPH at times. Some of the higher gusts included a 71 MPH gust in Audubon, 65 MPH gust at Farnhamville and on the mile long bridge across Saylorville Reservoir, 64 MPH at Adair and Boone, 63 MPH at Carroll, 61 MPH at Creston, 60 MPH at Algona, and 59 MPH at Ankeny and Windsor Heights. The winds caused whiteout conditions over western Iowa by the mid afternoon hours. Boone County declared a Civil Emergency as travel became impossible in the county. Nearly all roads were closed in the northwest quarter of the state, with travel not recommended over nearly all of the Des Moines CWA. Interstate 80 was closed for several hours from the Nebraska border to just west of Des Moines. Many of the counties across the northwest half of Iowa had to remove snowplows from the highways as it was to dangerous to continue until the high winds subsided. There were scattered power outages with the storm, but numbers were on the order of a few thousand customers during the peak. There was some freezing rain at the onset of the storm, fortunately the amounts were limited to a few hundredths of an inch at most so damage was limited. Much of the state did not have snow on the ground at the beginning of the storm. This limited the amount of blowing to some extent. Measurement of the snow was difficult. Most amounts were in the 4 to 6 inch range over the northern third and western third of the state, with 1 to 4 inch amounts common elsewhere. A narrow area of far northern Iowa reported 6 to 9 inches of snow for the 24 hour period. There was a wide variance of measurements however. As an example, a total of 4.4 inches was reported at the Des Moines airport, while an observer just 6 miles to the northwest only reported 0.6 inches. Temperatures plummeted as well. Readings that were in the 30s to mid 40s F in the early morning of the 11th, fell to the single digits and teens by the night of the 11th and early morning of the 12th. Wind chill temperatures fell to -10 to -30 F across the area as well.

Intense low pressure that was over northern Minnesota the previous day had moved into southwest Ontario, north of Lake Superior, during the day on the 27th. A lobe of low pressure rotated around the low as strong cold air advection took place over Iowa. Winds increased sharply after sunrise with wind gusts in excess of 58 MPH over a large part of central and north central Iowa. The strongest winds were recorded in central Iowa in Boone, Story, into Polk County. Winds gusted to 63 MPH in Boone, with 62 MPH winds in the Des Moines metropolitan area. The high winds overturned three semi tractor-trailer trucks, one in Boone County, one on Interstate 35 in Franklin County near Dows, and the other in Story County. All three drivers received minor injuries from the accidents. Scattered power outages were reported around the state. Outages peaked around 1000 customers during the afternoon hours. Minor tree damage was also reported around the state.

A very unstable airmass was in place over Iowa. Afternoon temperatures warmed into the upper 80s to mid 90s, with dewpoint readings in the upper 70s to low 80s. A weak boundary extended out of eastern Nebraska across northern Iowa. This boundary helped to focus moisture. At the same time, a negatively tilted shortwave lifted northeast out of the Rockies into Nebraska during the afternoon and early evening. The lifted index fell to -10 to -14 C by evening with CAPE rising to 5000-7000 J/kg in the very moist airmass. The freezing level was very high, between 16,000 and 17,000 feet. As a result, there was little in the way of hail. The downdraft CAPE was quite high, 800 to 1400 J/kg. Thunderstorms formed in northeast Nebraska. They rapidly formed into an upscale MCS, and eventually a full-fledged MCC. Precipitable water values were extremely high, in the 2.5 to 2.75 inch range. The primary mode of severe weather with the system was in the form of high wind. Wind gusts of 60 to 70 MPH caused sporadic damage across western into central Iowa with tree damage, as well as damage to outbuildings. The storms produced one funnel cloud in Carroll County. The high precipitable water values led to very heavy rainfall with widespread flash flooding. A swath of 2 to 5 inch rainfall extended from west central, through central, into parts of southeast Iowa. There were numerous reports of a foot or more of flowing water over streets. Following the flash flooding, water remained standing on many roads due to the soils across the state being nearly saturated. This resulted in some road closures. The Des Moines metropolitan area was hard hit as 3 to 5 inches of rain fell in 4 hours or less. This caused extensive flooding in the city. Some evacuations took place. One was at a trailer court along Four Mile Creek on the east side of Des Moines. Numerous roads were closed on the west side as well as Walnut Creek jumped its banks. In fact, the creek set an all-time record high stage. Fast rising waters of North Walnut Creek flooded four basement apartment units in Clive with water rescues taking place. Lightning struck a house in Adel, setting it on fire. The family was asleep at the time and were rescued by the fire department after the house had been on fire for 45 minutes. Damage to the house was around $1,000,000 as it was a total loss, burned to the ground. In Black Hawk County, lightning struck the water treatment plant in Cedar Falls. Power was knocked out, resulting in the discharge of 750,000 gallons of sewage into the Cedar River. Lightning struck the historical depot in Carroll, now the Chamber of Commerce, and caused minor damage to the roof. It also knocked out telephone service to 3 adjacent buildings.

A very unstable airmass was in place over Iowa ahead of an approaching cold front and short wave. The cold front itself was over South Dakota, and set off a line of severe thunderstorms in front of it. Over central into south central Iowa, extending into the northeast counties, strong to severe thunderstorms broke out shortly after peak heating. Daytime highs reached the mid 80s to mid 90s across the state with dew points in the upper 70s to low 80s. Precipitable water values increased to between 1.8 and 2.3 inches across the central counties. CAPE increased to 4000-5000 J/kg with lifted indices falling to the -8 to -11 C range. The atmosphere was moderately sheared with 35 to 50 kts of shear available. The LCL was a relatively low 500 to 1000 meters. Downdraft CAPE was 1000 to 1700 J/kg, with 700-1000 J/kg of CAPE in the -10 to -30 C layer of the atmosphere. The freezing level was between 15,000 and 15,500 feet. Thunderstorms fired in central Iowa and became severe quite quickly. One storm produced two tornadoes in the Indianola area of Warren County. One hit to the west of Indianola. Several houses were damaged near Euclid St and Y Street. Houses and barns were damaged at the intersection of R63 and Hover Street. The total number of homes damages was 22 with 5 sustaining major damage. The major damage included wall damage to homes, collapsed walls on garages, and uplift of decks and roofs. The wind speed was around 100 MPH. The second one touched down just east of the main part of town and caused building damage. Damage included inward and outward collapse of overhead doors to a garage and metal outbuildings. It was on the ground for less than one half mile and produced winds around 90 MPH. The storms went on to produce wind gusts in excess of 60 MPH in Marion and Jasper Counties. Damage was reported to farmsteads, as well as to trees and power lines. The storms were heavy rain producers. Heavy rain fell, with 2 to 3 inches of rain falling in about an hour over Warren County. Reports of 1 to 2 feet of flowing water over Highway 92 were received. Water stranded people in a trailer court west of Highway 65/60 south of Indianola. Attention turned to storms forming closer to the cold front. Strong to severe thunderstorms moved into northwest Iowa and produced severe weather after midnight in north central Iowa. Wind damage was reported in the Mason City area shortly after midnight. Heavy rainfall continued over north central Iowa. Parts of the area around Waterloo and Dewar received between 4 and 9 inches of rain over the previous 48 hours, 2 to 5 of which fell just prior to the flash flooding. The flooding closed roads in the area. Lightning struck a house north of Des Moines during the evening. Damage was limited, but circuits were blown out.

A very unstable airmass was in place over Iowa as a cold front approached from the west. High temperatures the previous day were in the upper 80s and 90s for the most part, with 101 at Fairfield. Dewpoint readings were in the 70s east to near 80 over the west. CAPE was in the 4000 to 5000 J/kg range with lifted indices of -8 to -11 C. Downdraft CAPE was quite high, 1200-1400 J/kg. CAPE in the -10 to -30 C layer of the atmosphere was between 300 and 500 J/kg. The atmosphere was quite strongly sheared with 45 to 60 kts of shear. Precipitable water was low, only 1 to 1.5 inches. With the relatively dry air, the LCL was between 1500 and 2500 meters. The airmass was also quite warm with the freezing level around 15,600 feet. Thunderstorms formed in two clusters. One extended from Minnesota southwest into eastern South Dakota. The other area was over central Nebraska. The convective area from South Dakota dropped southeast into Iowa during the late evening hours. It produced high winds and hail as it did. Hail was not the major mode of severe weather. Most of the larger hail occurred during the early stages of the storm. Golf ball size hail fell west of Graettinger in Palo Alto County for the largest hail report. The cluster of storms organized into a small derecho as it approached Fort Dodge. The derecho raced southeast through the Des Moines area and into southeast Iowa. It produced some hail as it did, but by in large high winds were the primary threat. Winds of 60 to 75 MPH were common, causing considerable tree damage. High winds of 65 to 75 MPH roared through Ames. A shelter at the Iowa State Veterinary Medicine School was blown over. Several horses were injured by the collapse. University officials has to euthanize one horse due to severe injuries. A measured wind gust of 84 MPH was recorded on the northwest side of the Des Moines Metro area. Power was knocked out to nearly 40,000 customers in central Iowa by the storms. Damage reports from along the path of the derecho were widespread. Grain bins were destroyed as well as numerous out buildings. Tree and power line damage was extensive all the way from the Minnesota border through south central Iowa. Heavy rain was also an issue with the storms. Rainfall of 1 to 2 inches per hour fell with the storms from Fort Dodge into the Des Moines area. Flash flooding was reported in Marion County. Heavy rainfall of 2 to 4 inches in under 2 hours flooded city streets in Knoxville, some 4 feet deep, with cars stalled in city streets. Water was also over the road southeast of Melcher-Dallas in Marion County. Flash flooding was reported in Webster City. Flooding blew manhole covers off and stalled several cars in the city. As the storm moved through the Raymond area of Black Hawk County, lightning struck a house. It blew a basketball size hole in the roof and caused electrical damage to the house and some structural damage to ceilings.

A very unstable airmass was in place over western Iowa and areas to the west. CAPE rose to over 6500 J/kg by late afternoon with the lifted indices falling to -12 to -15 C. Downdraft CAPE as quite high at around 1600 J/kg, while available CAPE in the -10 to -30 C layer of the atmosphere was between 700 and 1000 J/kg. The atmosphere had a strong shear present with 40 to 60 kts The freezing level was quite high, just below 15,000 feet. Precipitable water increased to around 1.5 inches. Strong thunderstorms developed over southern Minnesota. Initially, the thunderstorms moved east. Once they became more rooted in the boundary layer, they moved southeast and propagated nearly due south. The main severe threat was high winds, with numerous reports of tree, power line, and grain bin damage. Winds of 70 MPH were measured in Estherville for example. Seventy MPH winds were reported in Grundy County. The outflow boundary from the complex continued to move southeast, and actually moved all the way into Missouri. Scattered severe weather occurred with this. Seven power poles were snapped in Polk County by the high winds. A wind gust of 62 MPH occurred at the Ottumwa Airport. Flash flooding also became a problem with the antecedent soil conditions nearly saturated. Flash flooding in Emmet County resulted in the closing of Highway 4 near Wallingford and evacuations in the city. A secondary area of thunderstorms formed over northwest Iowa and moved east-southeast into the CWA. Heavy rains caused minor urban flooding in Calhoun County with 6 inches of standing water reported in the city of Pomeroy. Although many of the storms produced small hail, there were very few reports of hail larger than dime size. Reports of hail up to an inch in diameter were received in central Iowa late in the evolution of the system. Lightning struck a house east of Grinnell during the early morning hours around 0330 CST. The house was set on fire with structural damage and damage to contents estimated at $550,000.

The frontal boundary that moved through the state during the previous night retreated northwest and allowed the atmosphere to reload. CAPE rose to 2000 to 3000 J/kg by mid morning with downdraft CAPE values in the 1400 to 1600 J/kg range and available CAPE in the -10 to -30 layer of the atmosphere around 500 J/kg. The freezing level fell slightly from the previous night and was around 13,500 to 14,000 feet. Lifted indices were only in the -1 to -3 C range. The shear was about the same as the previous night, in the 20 to 35 kt range, however precipitable water values fell to 1.1 to 1.5 inches. As the warm air returned, thunderstorms developed before dawn. They increased in strength as a weak shortwave approached the area. The thunderstorms formed into a cluster over northeast Nebraska into western Iowa after sunrise. The small MCS took on a mini bow type configuration. Though there were a few reports of hail of up to an inch in diameter, the primary mode of severe weather was high winds from the bowing system. Wind speeds of 60 to 80 MPH were common along the leading edge of the storm. Tree damage was widespread over a several county wide area. Some property damage was done by the winds as well due to flying debris. The thunderstorms continued southeast into southeast Iowa during the late morning and early afternoon and weakened slowly. Another line of thunderstorms formed over northwest Iowa by late morning and continued into the mid afternoon hours. These storms produced high winds, heavy rainfall, and hail. The hail was generally around an inch in diameter, with the largest being golf ball size in Webster County. Golf ball size hail also fell in Warren County at Milo. Wind speeds were in the 60 to 65 MPH range for the most part, resulting in tree and power line damage. A tornado touched down in open fields in Madison county north of St Charles. The heavy rainfall resulted in some flash flooding as well. Soil conditions across the state were nearly saturated, so a quick 1 to 2 inches of rainfall caused local flash flooding in Black Hawk, Marion, and Tama Counties.

A strong push of warm air aloft took place over the central U.S. with 850 mb temperatures warming well above zero C over much of the state. During the day on the 19th a relatively strong high moved southeast to the east of Iowa. The easterly flow of cool air in the low levels established a strong inversion over the state. Surface temperatures fell into the teens and 20s in the cool easterly flow. A strong weather system from the southwest U.S. moved east across the southern half of the country during the night of the 19th into the daytime hours of the 20th. The low passed south of Iowa, however a strong push of warm and moist air moved into Iowa during the early morning of the 20th. A large area of freezing rain developed with embedded thunderstorms across southern Iowa during the early morning hours of the 20th. Thunderstorms produced moderate to heavy freezing rain and some small hail as they overspread the southern third of the state. The storms produced nickel size hail just south of Iowa shortly before sunrise. The area of freezing rain lifted north across Iowa through the morning hours. The event was not long lived, but did produce significant amounts of ice. The heaviest accumulation of ice occurred over the west central counties with Ida, Carroll, and Crawford Counties reporting three quarters to one inch of ice accrual. The ice of up to an inch thick extended as far east as Guthrie County and into a part of Adair County. The ice toppled large trees and knocked power out for thousands of customers. Wapello County also received three quarters of an inch of freezing rain as heavier thunderstorms moved through that area. Roads were ice covered and numerous schools and businesses closed due to the ice. Outside of the hardest hit areas, there were scattered reports of large tree branches being downed by the weight of the ice. Power outages numbered in the 50,000 to 60,000 customer range at the peak during the evening of the 20th. Thirty six hours after the event, over 40,000 customers remained without service. Due to the extensive damage, it was difficult to return service to some of the rural areas. Some of the rural areas were without power for several days to a week after the ice storm. There were still over 700 customers without power 9 days after the ice storm occurred. Most of the outages were in Sac and Carroll Counties. Freezing drizzle followed the main ice event. Though only very light additional accrual of ice took place, trees that were close to breaking continued to fall during the evening and resulted in the continued rise of power outages. On the 22nd, winds began to increase, resulting in additional damage. By mid afternoon on the 22nd, 60,000 customers were without power, and the counties of Sac, Carroll, Audubon, Calhoun, Cass, and Crawford had received a state disaster declaration. The ice storm broke approximately 2250 utility poles and knocked down nearly 1000 miles of power lines. Total damage to the Iowa Rural Electric Cooperatives alone was estimated at $35,000,000. One injury was reported in Sac County when a canopy at a gas station collapsed under the weight of the ice and fell on a woman. She was taken to the hospital for treatment. Her injuries were not life threatening.

Part 2 of 2: A major winter storm system affected the central U.S. during Christmas week. There were two upper level systems involved with this storm. The southern stream low dove into the southern U.S. and then turned northeast. The turn was sharper than is typical as the northern stream upper low pushed southeast. The southern stream and polar low interacted with each other, resulting in a Fuji Wara effect. The southern low turned north, then eventually northwest and moved from northern Louisiana into Iowa. This resulted in a considerable amount of warm air being drawn north over Iowa. Initially, freezing rain was widespread during the 23rd and early on the 24th, as was mentioned in the previous entry. Most of the CWA had some freezing rain, though the amounts were generally under one tenth of an inch over the southeast half of the state. Temperatures warmed above freezing on the 24th in all of Iowa along and east of Interstate 35 as warm air continued to flow north over the top of the easterly surface flow. An inverted trough developed during the day on the 24th, allowing colder air to begin filtering south over western Iowa during the day. The precipitation changed over to snow by the afternoon, with snow becoming heavy during the evening. Some freezing rain and sleet was mixed with the snow at times as well. The heaviest snowfall was over the far northwest, where nearly 12 inches was recorded from northwest of Algona in Kossuth County, to Pocahontas County. Over 10 inches fell in Pocahontas County near Rolfe, and also in Audubon County near Grey. Much of the western part of the CWA received 8 to 10 inches of snow from this system. In addition to the snow and mixed precipitation, winds increased from the north with speeds of 25 to 35 MPH common. In addition to the blowing and drifting problem created, a significant number of people lost power in west central Iowa as the ice laden tree branches began to break in the winds and downed additional power lines. Utility crews indicated that they were unable to keep up with the damage in Crawford, Carroll, and Audubon Counties until the storm subsided. In addition to the breaking tree branches, drifting made it difficult for the utility crews as well as anyone else driving. Many rural roads were closed by 4 to 5 foot snow drifts. Farther east, rain changed to snow during the evening of the 24th into the 25th, however accumulations were generally under 4 inches. On the morning of the 25th, the surface low pressure moved northwest into Iowa, bringing with it a lot of warm air. This changed the snow over to freezing rain and ice pellets for several hours. Though accumulation of ice pellets were one quarter of an inch or less, and ice accretion generally under one tenth of an inch, an area of heavier freezing rain moved through Polk County. An area from west central Polk County into the northwest received 0.2 to 0.3 inches of freezing rain before the precipitation changed back to snow. Following the storm event, the Governor of Iowa declared a state disaster for several counties in western Iowa. Crawford and Ida Counties received the state disaster declaration in the DMX CWA. Subsequent to the storm itself, high snow accumulations from the record snow storms across Carroll County during December caused the collapse of a hog building in rural Carroll County. The building housed 1200 hogs with thirty one of the hogs killed in the collapse.

An intense low pressure system moved into southern California during the afternoon and evening of the 7th, then tracked northeast across the central U.S. the surface low reached Kansas during the morning of the 8th, eastern Kansas by evening, and tracked to northern Illinois before sunrise on the 8th. The storm intensified rapidly, reaching 975 mb by the afternoon of the 9th as it crossed Lower Michigan. Snow broke out across Iowa during the overnight hours of the 7th into the early morning hours of the 8th. The snow continued through the day on the 8th. Northeast winds of 15 to 25 MPH caused drifting snow through the day and into the evening. Snowfall reached a inch per hour at times during several heavier waves of snowfall during the afternoon and evening of the 8th. A broad band of 8 to 16 inch snowfall totals were reported across much of the northwest two thirds of the state. Some of the heavier snowfall totals included 16 inches in Cass County at Atlantic, 15.7 inches at the Des Moines Airport, and 15.3 inches in Windsor Heights, both in Polk County. The entire CWA received at least 4-6 inches from the storm over a 36 hour period. Road conditions had become hazardous from the heavy snow on the day before. As the low moved to the east of Iowa and intensified, strong northwest winds developed across the state. Winds of 30 to 40 MPH were common with gusts of 45 to 60 MPH fairly common for several hours. A wind gust of 61 MPH was recorded at the ASOS at Estherville, while 58 MPH winds occurred at a mesonet site in Carroll. There were scattered power outages around the state, however at the peak about 8000 customers lost power. This was considerably less than the 350,000 that occurred during the blizzard in the spring of 2007. Visibility was reduced to near zero for a several hour period as there was plenty of loose snow to blow around. The winds produced 4 to 6 foot drifts in many areas, with reports in some of the rural areas of drifts of 10 to 15 feet. Roads drifted shut fairly rapidly. By the early morning hours, snow plows had to be removed from roads statewide as there was no way to keep up with the blowing and drifting snow. Interstate 35 was closed north of Ames along a 15 mile stretch, and Interstate 80 was closed along a 55 mile stretch east of Des Moines. Reports at sunrise on the 9th indicated that all rural roads in the state were closed and many of the arterial roads were closed as well. Periodically, the Interstate system was closed due to the blizzard conditions. Nearly all business in the state and all of the schools were closed on the 9th. Many schools remained closed on the 10th as well, with the list of schools closed exceeded 235 yet on the 10th. Conditions improved through the day on the 10th, however with all the extensive drifting that took place during the blizzard numerous roads remained snow clogged into the 11th. Five school districts remained closed on the 11th, and another 60 were on delayed start with no bus service beyond the main arterial roads. In the end, the blizzard and preceding snowstorm was described as the worst to hit Iowa in 40 years based on intensity and areal coverage.

A very warm, moist, and unstable airmass was in place over Iowa from 8th into the 9th. Surface temperatures on the 8th warmed into the upper 80s and 90s, with dew point readings in the 70s. A weak cold front moved into the state during the evening of the 8th and early morning of the 9th. There was little thunderstorm development initially as the airmass was capped. Temperatures at the 700 mb level were +14 to +17 C. During the early morning hours of the 9th, a short wave lifted northeast out of the southern Rockies. This resulted in cooling of the mid levels of the atmosphere, thus destabilizing the airmass. The cold front stall out during the morning of the 9th as a second short wave lifted northast. Eventually, the front moved south of the state on the night of the 9th. Overall lifted indices were in the -6 to -10 C range with CAPE values in the 3000 to 4000 J/kg range. Downdraft CAPE was in the 800 to 1400 J/kg range with 30 to 50 kts of shear available. CAOE available in the -10 to -30 C layer of the atmosphere was between 300 and 700 J/kg, with a freezing level of 14,000 to 14,500 feet. The LCL was relatively high across the area ranging from just below 1000 meters to about 1250 meters. Plenty of moisture was available with precipitable water values between 1.75 and 2.25 inches. Thunderstorms developed initially over Nebraska and tracked east-northeast into Iowa shortly after sunrise. One supercell continued to track across the state and produced a swath of wind and hail damage from Sac County east to Black Hawk County. Additional thunderstorms formed along the cold frontal boundary by mid morning and progressed into the state. The storms remained below severe levels for several hours, but did become severe by mid afternoon. A broken like of storms formed with two primary areas tracking east across central and southern Iowa. These two areas featured mini bow echoes. The predominant mode of severe weather in the afternoon was high winds. Several of the storms produced hail, but the hail was sub-severe. A long lived supercell Thunderstorm tracked across northern Iowa Sunday morning with the Highway 20 corridor receiving the brunt of the damage. Reports of quarter to golf ball sized hail were common with some hail stones reported to be in excess of two inches approaching the size of a tennis ball. The hail was wind blown as well, at speeds of 50 to 70 mph, making it extremely damaging and dangerous striping siding off houses and knocking out windows. A measured wind speed of 68 mph was recorded at a KCCI TV SchoolNet site near Jewell in Hamilton County. Significant hail damage was received all along the track with areas near Otho, Callender, Radcliffe, Eldora and Grundy Center hit particularly hard. In Eldora, many homes had windows broken out and tree and power line damage left the city without power. Winds of over 100 MPH toppled a communication tower in Eldora. A short time before the winds hit Eldora, a 102 MPH wind gust was recorded at the landfill northwest of town. Wind driven hail of 2 to 3 inches in diameter broke all siding and windows out on the north and west walls of most homes, with hail stones reported landing inside of houses. Damage in the town of Eldora was expected to be greater than the damage done in the town of Parkersburg by the EF5 tornado a year earlier. A 150 square mile area of crops was affected in Hardin County. Total losses were reported on 45,000 acres, with 60% or greater loss on another 55,000 acres. Hail damage in the Otho to Callender areas was described as the worst seen in 20 years. MODIS satellite pictures of the crop damage area included in this report. Estimates of crop damage from this one supercell were over $175,000,000. Governor Culver declared Hardin County a state disaster area within a day or two of the storm, and declared Webster County a disaster area about a week later. Formal paperwork was turned in to make 8 Iowa counties federal disaster areas, They were Calhoun, Grundy, Hamilton, Hardin, Ida, Sac, Webster, and Woodbury. Following the storms, a shelter was set up for those who felt they should not stay in their homes. Luckily the evening round of storms tracked south. Campers at nearby Pine Lake State Park, gathered for an archery event, were bruised by hail. There were 22 reports of injuries in Hardin County, 11 serious enough for people to be taken to hospital, but there are no known life threatening injuries. A second round of severe weather rolled roughly along I-80 between 1630 and 1800 CST, producing a lot of tree and power line damage but apparently little structural damage. As the storms moved through the metropolitan Des Moines area, winds damaged power lines and knocked out power to 12,000 homes. One storm produced a wet microburst in Union County. The winds took the roof and shingles off of a two story brick building near Afton. The afternoon round of storms produced some hail, but most of the hail was not severe as mentioned above, and was pea size or smaller. During the morning round of storms, lightning struck a building in Waverly. The lightning struck an antenna on the building and melted screws all the way down the side of the building, starting a small fire and blowing hole in the wall.

A semi-stationary frontal boundary remained in place across southern Iowa while a secondary boundary was stretched from eastern South Dakota into northeast Iowa. The airmass became very unstable with lifted indices falling to -10 to -15 C and most unstable CAPE rising to 5000 to 6000 J/kg. Zero to 3 km CAPE rose to over 200 J/kg in northern Iowa by the late afternoon. Surface temperatures rose to the 80s to low 90s, as dew point values reached the upper 60s to mid 70s. Wind fields were somewhat weak, however effective shear was in the 35 to 50 kt range by late afternoon. The amount of CAPE in the -10 to -30 layer of the atmosphere rose to over 400 J/kg by late afternoon. Thunderstorms erupted in two places initially. The first was along the northern boundary. However the severe storms with this round remained to the north of Iowa. A second round formed north of the southern boundary along the edge of the mid level cap. The storms became severe and produced high winds and hail. Thunderstorms from farther west moved into Iowa later in the evening and became severe. The storms produced a weak Derecho. Widespread winds of 60 to 70 MPH occurred with these storms, along with numerous reports of hail of 1 to 2 inches in diameter. The initial round of storms produced large hail and gusty winds from southwest into central Iowa. The second round resulted in winds of 60 to 70 MPH and large hail from central into southeast Iowa. The highest wind gust was 74 MPH, measured at an RWIS site near Ankeny in Polk County. The wind damage was largely to trees and power lines, with spotty reports of small shed and minor building damage. A semi-tractor trailer was blown off of Interstate 35 near Highway 210 in Story County. The high winds ripped siding off of a house in Ankeny in Polk county, and windows were blown out of a house in Colfax in Jasper County. Thunderstorms rekindled on the back side of the main thunderstorm area after sunrise. A few storms became severe and produced 60 MPH winds and golf ball size hail as they moved from The Fort Dodge area into Story County.

A nearly stationary frontal boundary was in place across Iowa. It extended from the southwest corner of the state, northeast to near Des Moines and Davenoprt. There was a sharp contrast across the boundary with temperatures in the 50s north of the front and upper 70s to low 80s south of the front. Dew points climbed into the mid to upper 60s. Most unstable CAPES were in the 2000 to 4000 J/kg range with lifted indices of -4 to -9 C. Downdraft CAPE was in the 800-1000 J/kg range with an effective shear of 50 to 65 kts. The LCL was relatively low at 750 to 1000 meters. Significant CAPE was available in the -10 to -30 C. layer of the atmosphere and was between 400 and 900 J/kg. Plenty of moisture was available with precipitable water values of 1.4 to 1.6 inches. Thunderstorms fired up during the late afternoon. The main event was a small cluster of supercells. When the first cell formed, a tornado touched down briefly in Cass County west of Anita. It was a landspout and was only on the ground briefly. Damage from a weak EF0 tornado took place through corn fields near the intersection of R Ave and 278th St in Dallas County. The weak path continued for about 1.5 miles east with the most intense damage along 270th St. A 30 yard convergent path of severe tree damage was observed through a residence there. The tornado lifted shortly after that. Fallen trees damaged a garage and vehicles at this residence. The mesocyclone weakened after this. As the storms progressed east it left a path of high winds and hail along its path. The storm hit the northwest side of the metropolitan Des Moines area and produced tornadoes in Dallas and Polk Counties. The storm produced winds of 60 to 80 MPH and produced considerable tree and power line damage. A semi-tractor trailer truck was blown off of U.S. Highway 30 in Tama County. Storms continued to fire into the night. A round of thunderstorms moved across southeast Iowa and produced golf ball size hail in Davis County in the Bloomfield area. High winds in the Bloomfield area damaged several businesses, knocking out windows. A partial roof collapse was reported at an area school. The combination of wind and hail broke out all of the windows on the west side of buildings in the downtown business district.

A late season snow event took place over Iowa during the day on the 5th. Strong low pressure developed over Kansas on the 4th and advanced northeast into northwest Missouri by the early morning hours of the 5th. The low then moved east-southeast to be over southern Illinois by the evening of the 5th. A strong push of warm and relatively moist air took place ahead of the low, while cold air moved in on the back side of the surface low. Initially, precipitation with the system was in the form of rain showers and isolated thunderstorms. The airmass was unstable with showalter indices around -4 C. across the south half of the state. As the cold air settled southeast, the rain changed over to snow from the northwest with a brief period of ice pellets occurring during the changeover. Once the rain changed over to snow it became heavy with visibility reduced to one quarter of a mile or less at many locations. At the same time, northeast to north winds of 25 to 35 MPH with higher gusts accompanied the snow. Temperatures remained at or a little above freezing during the event, which limited the amount of blowing snow. During the late morning and early afternoon hours, a line of thunderstorms developed in the deformation band snow between Story City and Waterloo. Reports of snowfall rates of over 5 inches per hour were received. As the storms moved across Interstate 35 north of Story City, 3 inches of snow fell in a 30 minute period. This resulted in numerous accidents and subsequently a 18 mile long section of the interstate was closed for a period of 3 hours due to gridlock. The interstate was closed north of Story City to U.S. Highway 20. A band of 6 to 10 inches of snowfall took place in the thunderstorm area from near Boone in Boone County to Conrad in Grundy County. Some of the heavier snowfall totals included over 10 inches in Grundy County at Conrad, 10 inches in Hardin County at Eldora, 8 to 9 inches in Hamilton County at Jewell, and around 7 inches in Hardin County west of Iowa Falls, Hamilton County south of Williams, and in Boone County south of the Boone Airport. In addition to the numerous accidents caused by the heavy, wet snow, scattered power outages also occurred as the snow took down tree limbs in a few places.

A strong cold front moved through the state during the early morning hours of the 27th. Temperatures fell from the 50s into the upper 20s to low 30s within an hour or two. The cold air was very shallow with warm air continuing to stream into the state. A large area of thunderstorms developed on the cold side of the cold frontal boundary. The rain fell into the cold air at the surface, resulting in widespread glazing across much of the southeast half of the Des Moines CWA as temperatures had fallen into the 20s by the time the thunderstorms moved through. Ice accumulated quite quickly with one quarter inch amounts quite widespread. Spotty one half inch amounts were reported over parts of central, south central, and southeast Iowa as thunderstorms produced heavier rainfall in those areas. Scattered power outages were reported across the area and roadways became treacherous due to the icing. Overall, damage was not all that extensive as the areas that received half inch amounts of ice were relatively small.

The seasons first strong push of cold air moved south into the central U.S. on the 26th. A very strong upper level trough of low pressure aloft dropped south out of Saskatchewan accompanied by a strong upper level jet stream and a tropospheric fold. As the cold air moved in, the atmosphere became adiabatic, creating a mixed layer, up to the 700 mb to 600 mb level. The mixed layer contained very strong winds of 60 to 70 kts. The downward momentum in the subsidence area behind a cold front that moved south across the area produced high winds over a large part of the state. Most areas reported sustained winds of 40 to 45 MPH for several hours, with many areas reporting gusts of 60 to 65 MPH. The highest gust was recorded in Polk County in West Des Moines with a gust of 69 MPH. Some of the other higher gusts occurred in north central Iowa with a 68 MPH wind gust in Cerro Gordo County at Ventura, and in Polk County in Windsor Heights. Scattered damage was reported around the state with numerous tree branches broken and some trees blown over. Power was knocked out in several locations. In the Des Moines metropolitan area, about 17,000 homes were without power at the height of the storm. Power was out for 3 to 6 hours in most cases. Thousands of homes were without power for brief periods of time during the wind event. In Black Hawk County, at Dunkerton, the high winds caused severe damage to a nearly completed new COOP with damage estimated over a million dollars. The new COOP was under construction following the damage earlier in the spring as a tornado destroyed the old one. There was some crop damage as well as the high winds caused lodging of some of the corn around the state as the harvest was not yet complete. During the afternoon of the 26th, the high winds caused some travel problems as it was difficult to maintain control due to cross winds. The mile long bridge across the Saylorville Reservoir near Polk City, in Polk County, was closed for several hours due to the high winds for safety reasons.

A cold front had moved south of Iowa during the afternoon and evening of the 4th, however the airmass in the vicinity of the front was capped. It remained very unstable over Iowa with CAPE in the 3000-5000 J/kg range and lifted indices from -7 to -11 C. There was considerable downdraft CAPE available with values around 1300 J/kg. CAPE in the -10 to -30 C. layer was quite high in the 900 to 1200 J/kg range. This was plenty to overcome the high freezing level of 15,200 feet. The atmosphere was quite strongly sheared for early August with 40 to 45 kts of shear. Deep moisture was also in place with a little over 2 inches of precipitable water present. A small area of thunderstorms erupted rapidly shortly before midnight from west central toward central Iowa. They became severe in central Iowa and advanced east across the state. The storms produced penny to quarter size hail at several locations, and smaller hail at numerous locations. Within a relatively short time of the storms becoming severe, under an hour, they began to produce high winds. Scattered gusts of 60 to 65 MPH were reported from Polk County to Mahaska County. Some tree damage occurred with the winds. Two power poles were blown over in Marion County near Harvey and an outbuilding was toppled near Pella.

A very unstable airmass was in place over Iowa as a warm front lifted north slowly into the state. The warm air had moved in aloft as freezing levels increased from 14,600 feet in the morning, to 16,200 by the evening hours. The atmosphere was a high CAPE, moderate to high shear with CAPE rising to near 5000 J/kg by late afternoon. Lifted indices fell to -8 to -13 C. A speed max moved across the state during the late afternoon and evening hours with shear increasing to between 45 and 60 kts. Downdraft CAPE was in the 1000 to 1400 J/kg range with available CAPE in the -10 to -30 C. layer of the atmosphere in the 800 to 1200 J/kg range. The LCL during the evening was around 1000 meters. A cluster of thunderstorms formed by the mid afternoon hours over northern Iowa. The storms propagated and grew to the southeast with all phases of severe weather occurring during the late afternoon and evening hours. Three tornadoes touched down. The strongest was in Polk County just southwest of Elkhart. The tornado damaged 2 houses and caused considerable tree damage. Parts of the house were blown up into the trees. The other touchdowns were relatively minor with one touching down briefly near Valeria in Jasper County, another just south of Newton in Jasper County. Straight line winds derailed 21 cars of a Burlington Northern train west of Albia. The storms formed into a forward propagating MCS and beta bow element before reaching central Iowa. An 82 MPH wind gust was recorded by a schoolnet site just east of Boone. There were numerous reports of winds to around 70 MPH as the storm moved south across the east side of Des Moines, and on southeast into southeast Iowa. Tree damage along the length of the bow echo was widespread with numerous uprooting reports, trees down, and power poles knocked down. In Poweshiek County, high winds north of Montezuma hit a farm. The barn was toppled completely. Surprisingly, a donkey that was in the barn walked out without a scratch. Most of the hail with the storm was around an inch in diameter. There was a report of 2 inch diameter hail in the New Virginia area of Warren County. Several golf ball size hail reports were received over southern Iowa as the air column cooled by the rainfall. Flash flooding became a problem in parts of southeast Iowa where rainfall of 2 to 3 inches fell in a short period of time. Many of these areas were areas that had been hit by heavy rainfall just a few days before. In Wayne County, 2 to 3 inches fell in parts of the northwest sections of the county, washing out a gravel road southwest of Derby. The storms moved southeast of the state by late evening...however thunderstorms re-fired in a line extending from near Ottumwa, through Ames, toward Fort Dodge. The storms produced hail and heavy rain with baseball size hail reported just south of Boone for example. Hail of 2.5 inches in diameter fell in Marion County at Knoxville as well. During the night, the storms continued to develop farther to the west. They produced hail up to golf ball and larger in size in Crawford. One storm produced softball size hail west of Kiron around sunrise. As the night progressed, the pattern transitioned to more heavy rain than severe weather. Flash flooding occurred as lines of thunderstorms trained across the same areas for a several hour period. Rainfall from the storms was anywhere from 3.5 to 7 inches in several areas with 6.73 inches in Guthrie Center one of the higher amounts. An unofficial report from near Brushy Creek, about 4 miles north of Guthrie Center, indicated rainfall of 8.3 inches. In Stuart, a report of 7 inches was received, while in the metro Des Moines area the highest total was 4.48 inches in Ankeny. River and stream flooding became a problem during the day on the 28th with several rivers reaching moderate flood stage. Major flooding occurred on Four Mile Creek in Des Moines.

A very unstable situation set up during the afternoon and evening of the 20th as a frontal boundary and remnants of the outflow boundary was established across southern Iowa. Temperatures warmed into the low to mid 90s across southern Iowa along and just south of the boundary. Dewpoint readings soared into the mid 70s to low 80s by evening. This resulted in very unstable CAPE values in the 5000 to 5500 J/kg range, and lifted indices of -10 to -13 C. during the evening. A low level jet of 40 kts set up while the atmosphere showed fairly strong shear, in the 40 to 55 kt range. There wasn't as much deep moisture as had been present in previous days with 1.3 to 1.6 inches of precipitable water. The freezing level remained quite high at around 14,600 feet and CAPE in the -10 to -30 C. layer of the atmosphere was only 300 to 500 J/kg. Downdraft CAPE was considerable however with 1000 to 1500 J/kg available. The LCL was also higher than it had been the previous day and was between 1500 and 2000 meters. During the evening, thunderstorms formed rapidly over northern Nebraska and far southern South Dakota to the north of the boundary. By late evening, additional development took place across Iowa. For the most part, these storms remained just below severe levels. One of them produced one and one quarter inch diameter hail over central Iowa however. The main event was the MCC from Nebraska. The MCC moved into Iowa after midnight and produced high winds and hail as it moved through. A portion of the system became a Derecho over west central Iowa and advanced across the state during the early morning hours. Winds of 60 to 75 MPH were common, with a few gusts estimated as high as 100 MPH in central Iowa. A radio tower was blown over by the winds in the Dawson area of Dallas County. Tree damage was very extensive from the winds with local utilities reporting as many as 200,000 homes were without power following the passage of the system. In Jamaica, in Guthrie County, 50 percent of the trees in town were damaged with 30 trees completely down. The roof was damaged at the race track there. The Guthrie County mobile EOC was tossed 150 feet into a field and roads were impassible. In Polk County, in Ankeny, 20 tO 30 Black Locust trees of 1 to 2 feet in diameter were snapped or uprooted near the intersection of 35th street and Highway 415. Winds estimated at 100 MPH in Dawson, in Dallas County, caused considerable damage. Roads were blocked by trees, with heavy equipment required to clear them. LP tanks were leaking in town as they were thrown about and damaged by trees. The grain elevator in town was also damaged. Bulldozers were also required to clear streets of tree damage in Boone County at Madrid. In Polk County, at Mitchellville, the roof was taken off of a modular building at the Mitchellville Correctional Facility. Lightning struck a house west of Nevada in Story County, setting it on fire. A second house was struck by lightning in Poweshiek County in Montezuma. Minor damage was reported to the building.

A frontal boundary remained across the area on the 19th as a shortwave moved into the area and interacted with the front. A low pressure wave formed on the front and lifted northeast across the state during the late afternoon. As the front sagged south, a line of thunderstorms formed and moved east-southeast through Iowa. The airmass became very unstable by late afternoon with CAPE in the 3000-4000 J/kg range and lifted indices in the -6 to -10 C range. Surface dewpoints rose into the low to mid 70s ahead of the front with temperatures in the 80s. The freezing level was quite high at around 15,000 feet and the CAPE in the -10 to -30 C. layer of the atmosphere was around 500 J/kg. Unlike in previous days, there was moderate shear in the atmosphere with 35 to 45 kts. Precipitable water was around 1.7 inches. The LCL was relatively low, at around 750 meters. The thunderstorms became severe quite rapidly and produced wind gusts to around 60 MPH. Hail was limited in size by the warm and moist atmosphere. Most of the hail was around three quarters of an inch or less, with the larger hail around an inch in diameter. There there three tornadoes during the event. The first touched down in Kossuth County, south of Algona, and did only minor damage with trees uprooted. The second was in Carroll County from the Templeton area toward Coon Rapids. This tornado caused more damage along its track. On one farmstead, it hit the house and barn. The barn was completely flattened, and damage was done to the house. Power lines were also downed. The main line of storms moved out of the state by around midnight. During the night, as the low level jet strengthened, the front began lifting north again. A scattered line of thunderstorms formed from west central into central Iowa. One of the storms produced penny size hail in the Huxley area of Story County.

Low pressure developed over Kansas with a strong southerly flow of very moist air streaming into Iowa ahead of it. Surface temperatures warmed into the 80s with dew point readings in the low to mid 70s. A semi-stationary front extended northeast from the low, across northern Iowa during the afternoon into the evening hours. The atmosphere became very unstable with MUCAPE in the 4500 to 5000 J/kg range by mid afternoon and lifted indices around -7 C. The shear was quite high, between 40 and 70 kts. Downdraft CAPW was between 1000 and 1300 J/kg with cape in the -10 to -30 C. layer of the atmosphere around 400 J/kg. The LCL was in the 750 to 1000 meter range, with the lowest over north central Iowa. With the exception of one hail report of 3 inch diameter hail report in north central Iowa, hail size was somewhat limited by the freezing level of 15500 to 16500 feet. A very strong transport of moisture took place on a 50 to 75 kt 850 mb jet. Precipitable water values soared to 1.6 to 1.9 inches by evening. During the initial phase of the severe event, high winds and hail were reported along the line of thunderstorms that formed from northern into west central Iowa. There were four reports of tornadoes in Worth, Winnebago and Cerro Gordo Counties during the afternoon hours of the 7th. This was with the initial round of storms. One of the tornadoes in Winnebago County destroyed a hog confinement building containing 3500 hogs. Several of them were killed and the remaining hogs needed to be taken to slaughter. The event transitioned into a flooding event overnight, then tornadoes began again during the afternoon of the 8th. A tornado touched down in Taylor County. Windows were blown out of houses there and several trees were twisted and blown down around the house. A pole shed was completely destroyed south of Ferguson in Marshall County. A stronger tornado was on the ground north to northeast of Ottumwa. A home lost a roof, with a wall of one room partially collapsed by the tornado. Several trees were also downed around the home. The event transitioned into a major Flood/Flash Flood event during the evening and early morning hours with many locations reporting 1 to 2 inches of rainfall, and spotty amounts of around 5 inches in just a few hours time. The line moved very little for a period of several hours. During the predawn hours, the line became broad and weakened to generally below severe limits. A new round of thunderstorms from Nebraska, which was the southwest part of the extensive line, moved into west central and southwest Iowa. The storm generally remained below severe levels for the most part, but they did produce very heavy rains. Another line of thunderstorms formed/re-intensified along the frontal boundary by the early afternoon hours. Initially, the storms produced strong winds and some small hail. As they moved southeast, several reports of high winds to near 70 MPH and a few reports of tornadoes were received. The most significant weather feature with this event was the heavy rainfall. The antecedent soil conditions in Iowa were extremely wet, such that flash flooding was caused by rainfall of an inch or more in an hour, even in rural areas. Heavy rainfall of 3 to 6 inches occurred in a broad swath extending from west central into north central, and parts of central and northeast Iowa. This resulted in widespread flash flooding. Eventually, the rain lead to major to record flooding along many of the rivers in the state. At one point or another, about 40 of the DMX 51 counties in the CWA were under flash flood warning. The situation was very serious over the north central and northeast counties. A levy was breached in the Mason City area as the Winnebago River rose to 3 feet over the record stage. The city was inundated by water. The water treatment plant was under water and non operational, all power was lost to the power grid in the city. The river cut a new channel and changed course into the downtown area. In the New Hartford area, a dam broke on Beaver Creek, resulting in the water level rising 2 feet above the all-time record level. High water along the mainstem Cedar River also caused communities to lose water. Nashua lost water as the water plant became flooded. Flooding along the Shell Rock River resulted in water supply loss in the town of Rockford. There was one death that resulted from the flooding. A 33 year old man died as he drove into flood waters in Interstate 35 at mile post 141 in Hamilton County. A second death occurred in Wright County as a 50 year old male farmer near Galt was sucked into a culvert by flood waters as he checked the field tiles in his farm field.

A very dynamic weather situation unfolded during the 5th into the 6th. Although the atmosphere was summer like in the lower elevations, the upper levels were more typical of April. A strong upper level low pressure area lifted northeast out of the southern Rockies with a negatively tilted trough of low pressure lifting northeast across the central U.S. An intense low pressure area developed over northern Kansas and lifted north into southeast North Dakota by the morning of the 6th, with a central Pressure of 984 mb. During the day on the 5th, the atmosphere was capped with the freezing level rising to 15,600 feet by the evening hours over central Iowa. A warm front lifted north across Iowa, with temperatures warming into the mid 80s to the south of the front with dewpoint readings in the low 70s. It became quite unstable by evening with MUCAPE between 2500 and 3000 J/kg and lifted indices in the -5 to -9 C. range. Considerable shear was available with the effective shear between 40 and 65 kts by evening. Downdraft CAPE was between 800 and 1400 J/kg across the CWA, with 400 to 500 J/kg of CAPE available in the -10 to -30 C. layer of the atmosphere. The airmass became very moist by evening with 1.6 to 1.9 inches of precipitable water available by evening. The LCL fall to between 750 and 1250 meters. Thunderstorms erupted to the southwest of Iowa in central Kansas, along the dry line there. The storms raced northeast into Iowa by sunset. In spite of the dynamics that were in place, the amount of severe weather was relatively limited. Hail was limited by the high freezing level and lack of supercellular development. Several of the storms produced small hail and a few produced high winds. There were several reports of brief tornado touchdowns, but little in the way of damage was reported for the most part. The first tornado touched down in Cass County and was only on the ground briefly. Another tornado touched down in Union County. The tornado took the roof off of an outbuilding and knocked down some power lines. The strongest tornado was on the ground for over 18 miles in Warren and Marion Counties. The tornado track was over open country for the most part and damaged outbuildings and one house. Three other tornadoes touched down in Jasper County, causing some moderate damage. The most significant feature with this event was the flash flooding. Soil conditions across the state were very saturated. Any significant rainfall resulted in flash flooding. A narrow band of heavier rainfall stretched from south central into central Iowa. Flash flooding occurred in the Des Moines metro area as the airport recorded 4.15 inches of rainfall for the day, with about 3 inches falling in two hours. Reports of severe street flooding were received with numerous reports of manhole covers being blown off. During the event, high winds occurred over the far northwest part of the CWA as the surface low intensified rapidly and the gradient tightened. A window was blown out in Pocahontas County, with tree and power line damage done in Emmet County. A barn was also damaged near Gruver in Emmet County by the high wind.

A strong upper level weather feature moved into the southwest U.S. as upper level ridge took place over the southeast U.S. This placed Iowa in a strong southwest flow of air aloft. At the surface, a shallow layer of Arctic air was in place with surface high pressure located over the north central U.S. Deep moisture was drawn north into Iowa over the top of the Arctic Air at the surface with a deep layer of above freezing air flowing the top of the cold low level air. Precipitatable water values rose to more than 2 times the normal for mid December. A large area of freezing rain developed by the late evening hours over southern Iowa. The rain spread northeast rather rapidly over much of the southeast half of the state during the early morning hours. One quarter of an inch or more of ice accrual took place southeast of a Waterloo, Boone, to Atlantic line. Ice accumulated to at least one half inch southeast of a Tama, Dallas Center to the southeast corner of Cass County. The heaviest ice accumulations took place over south central Iowa from just south of Des Moines, southwest to Taylor County and east toward into Wapello and Davis Counties. Snow fell along the north edge of the freezing rain area. A band of 2 to 4 inch snow occurred over a large part of northern Iowa. Numerous trees and power lines were downed from about Interstate 80 south. Power outages were very numerous as well with Alliant Energy reporting 40,000 to 45,000 customers without power at one point, and MidAmerica Energy reporting nearly 30,000 out at one point. Tree damage was described as incredible by one observer in Monroe County at Albia. Damage was quite extensive over southern Iowa, especially from U.S. Highway 34 south, and up into Warren County. The Des Moines International Airport was closed for a 6 hour period as a plane slid off the tarmac in the icy conditions. No injuries were reported at the airport. The ice caused $200,000 damage to the Southern Iowa Electrical Cooperative. Due to the severity of the storm, Governor Chet Culver declared 23 southeast Iowa Counties disaster areas.

The seasons first major winter storm moved into Iowa on the 1st. The system developed in the east Pacific off the California and Mexico coasts and lifted northeast into the central U.S. A very strong push of warm air moved into the central U.S. ahead of the storm. Prior to the storms arrival, polar air was in place with temperatures in the teens and 20s and dew points in the single digits above and below zero. Precipitation moved into the area during the predawn hours on the 1st. Initially the precipitation fell as snow, but with the intense warm air advection it turned to freezing rain and sleet very quickly over southern Iowa, and within a few hours after inception over the north. Surface temperatures were slow to warm due to evaporative cooling. In spite of winds in the low levels between 900 and 800 mb being in the 70 plus knot range, surface temperatures warmed very slowly. Eventually, the surface low pressure system lifted northeast through west central into northeast Iowa resulting in temperatures rising above freezing in most areas. Freezing rain was widespread over much of the south two thirds of iowa. Widespread ice accretions of at least one quarter of an inch of ice were reported. Heavier icing occurred southwest of Des Moines in Adair and Madison Counties with widespread ice accumulations of up to three quarters of an inch. One half to three quarter inch ice accumulations were common across the south tier of counties from Interstate 35, east. The ice resulted in some tree and power line damage with scattered power outages reported. Southeast winds of 20 to 35 MPH caused branches to break, knocking out power for thousands of customers by the afternoon of the 1st. Ice and ice pellets produced very slippery runway conditions at the Des Moines International airport. One plane slid off the tarmac, resulting in a 7 hour closure of the airport. The secondary problem that took place over nearly all of Iowa was heavy ice pellet accumulations. Many areas reported one half to 1 inch of sleet accumulation, resulting in considerable travel difficulties. Over the northern part of the state, roughly from U.S. Highway 20 north, one to three inches of snow fell, with spotty amounts of up to 4 inches. In addition to the snow, sleet was reported for several hours during the afternoon with accumulations of up to one half inch. Freezing rain did occur as well, but the freezing rain was not all that extensive or heavy.

Following the morning convection, there was little break before the cold front mentioned in the previous narrative moved into the state. The cold front advanced across the state accompanied by a strong upper level short wave. Severe parameters were not all that impressive, however it was a case of low top convection close to the upper low. The zero to 1 km helicity was quite high, in the 350 to 400 J/kg range and there was significant shear with effective shear in the 50 to 60 kt range. Other parameters were not all that impressive with most unstable CAPE in the 500 to 1000 J/kg range and lifted indices between zero and -3 C. The downdraft CAPE was around 500 J/kg with only about 100 J/kg of CAPE available in the -10 to -30 C. layer of the atmosphere. The LCL was quite low given the saturation caused from the previous convection. It was between 750 and 1000 meters. As the line of convection from the morning shifted to the east, a narrow line of strong thunderstorms developed along the cold front and the approach of the upper low. Initially, downburst winds occurred with the line with winds estimated around 65 MPH south of New Market in Taylor County. A short distance to the west of the CWA, a 75 MPH wind gust occurred at an RWIS site. As the storms raced east they produced gusty winds and very heavy rainfall. The storms produced a small, but intense, tornado in downtown Des Moines. Two power poles snapped and power lines down at 13th and Mulberry. At 6th and Mulberry, two vehicles were flipped including one SUV that was likely flipped nose down due to engine weight. The SUV slid about 30 feet. Eyewitness saw a small 10 foot tree lifted into the circulation and rotating around briefly. Media reported some roof debris on the SW 9th overpass at Martin Luther King Parkway, but no building damage is evident at this time. Some buildings were damaged in the area. Multi story and roof damage would be difficult To see from the street. The tornado was rated an EF1 with 110 MPH winds. This was the first tornado to touchdown in the Des Moines city limits since 30 May, 2000. High winds hit just east of the Des Moines Airport, blowing out the windows of 6 cars in a parking lot. As the storms moved east, another tornado touched down near the town of Seymour, in Wayne County. A farmer reported seeing a tornado touch down just southwest of Seymour. The tornado tore metal roofing off his shed. The tornado curved through town, blowing open doors at a school but causing little damage to the school. Windows were blown out of a church and a large tree feel to the west, knocking out power. A fabric roof was partially torn off a hoop storage shed at the elevator in town. A few trees were also topped. Path was very narrow and intermittent No other damage in the county. The tornado was rated an EF1 with 95 MPH winds. Two other small tornadoes touched down in Mahaska County. One was east-northeast of Bussy and was on the ground for about 4 minutes. The tornado tracked through open fields and only did agricultural damage. The second was an anti-cyclonic tornado that touched down briefly in an open field southeast of Bussy.

Strong winds aloft were in place over Iowa with a strong southwest flow of 35 to 55 kts in place through the lower and middle levels of the atmosphere. A cold front approached Iowa from the west during the afternoon and evening hours. The airmass was not all that unstable, with limited CAPE available for the event. Most unstable CAPE values were in the 1000 to 1500 J/kg range with shear values around 45 kts. There was a decent amount of downdraft CAPE available, in the 1000 to 1200 J/kg range. Morning convection complicated the weather situation by reducing the solar insulation across the area. Eastern Iowa did clear out enough to allow temperatures to warm in to the mid 80s, along with dew point temperatures in the mid 60s. A line of thunderstorms formed along this discontinuity during the last afternoon. This line lifted northeast quite rapidly, producing high winds as it did. A strong short wave lifted out of the southern plains during the late afternoon and evening hours. This in combination with the approaching cold front resulted in a strong line of thunderstorms along the front in western Iowa. As the storms advanced east, several small bow echo segments and meso-cyclones developed, resulting in high winds for parts of west central into central Iowa. Both of the lines of storms featured high wind as the mode of severe weather. Wind gusts were recorded in the 60 to 70 MPH range with the storms as strong winds from aloft mixed into the outflow of the storms. Several reports of tree and power line damage were received. One of the storms in Wayne County removed some shingles from a roof of a house and tore off a half sheet of plywood from the chimney.

A very unstable airmass remained in place across Iowa on the evening of the 6th with an east-west boundary lying across the mid section of the state. CAPE rose to around 4000 J/kg by late afternoon as afternoon highs reached the upper 80s to low 90s, and dew point temperatures were in the mid 70s to low 80s. The freezing level was very high, between 16,000 and 16,500 feet, reducing the threat of hail even though the CAPE in the hail layer, -10 to -30 C. layer, was in the 500 to 700 J/kg range. Downdraft cape was significant at around 1200 J/kg. The lifted index fell to between -4 and -8 C. by late afternoon with an effective shear of 35 to 45 kts across the area. LCL values were between 750 and 1000 meters. There was copious amounts of moisture in the atmosphere with between 1.7 to over 2 inches of precipitable water. Heavy rainfall was the most significant threat. Heavy rainfall of around 3 inches occurred in Cass County. The town of Griswold recorded 3.6 inches of rain. This resulted in flash flooding in the Griswold area. Reports of 4 feet of water running over the highways were received. Two to three inches of rain fell in Audubon County, with water running over Highway 173 southeast of Kimballton. Severe weather was spotty. Thunderstorms winds downed trees in Cass County from Griswold to about 3 miles northeast of Griswold. There was also a 60 MPH wind reported northwest of Griswold. Later in the evening, the thunderstorms moved east into central Iowa. One storm produced a microburst northwest of Van Meter in Dallas County. The winds blew in a garage wall and tossed the roof down on a nearby car. An uninstalled modular home was demolished along with several trees being downed. As the storms developed east into the metro Des Moines area, lightning struck a house in Urbandale starting it on fire. There were no injuries. In addition, lightning struck a garage in Denison, setting it on fire. The garage was destroyed along with numerous vehicles inside. Later on, thunderstorms moved across southwest Iowa. One of the storms struck a chicken barn in Taylor County. The lightning bolt blew a whole in the electrical box and set the chicken barn on fire. The barn was destroyed, but fortunately it was empty at the time. The lightning also knocked out the power at a nearby hog building, killing 700 young pigs due to lack of ventilation when the fans went out.

A warm, moist, and unstable airmass was in place over Iowa on the afternoon of the 21st. A Warm front lifted north into the state with temperatures rising into the upper 80s to low 90s south of it with dew point temperatures in the upper 60s to low 70s. This combination produced most unstable CAPE values in the 3000 to 4000 J/kg range and lifted indices in the -9 C. range. The environment was not strongly sheared with 25 to 35 kts of effective shear. The freezing level was quite high at 14,700 feet. In spite of this, there was plenty of cape in the -10 to -30 C. layer of the atmosphere, with 500 J/kg available. The LFC in the 1200 to 2000 meter range. The MCS developed rapidly and move east-southeast across Iowa. Many of the storms produced significant hail, with hail size ranging from nickel to over tennis ball size. Two and one half inch diameter hail fell north of Renwick in Humboldt County. Golf ball size hail fell in Hancock County in the Corwith area. The largest hail occurred during the first couple hours of the systems development. Most of the hail was in the three quarter to one inch diameter range later on. Four tornadoes were reported with the system. All of the were brief touchdowns however and caused little damage. One touched down in Wright County near Eagle Grove. Two others touched down in Butler County one west of Shell Rock, the other north of Steamboat Rock. The fourth tornado touched down northwest of Kelly in Story County. The final tornado touched down on the south side of Waterloo in Black Hawk County. Many of the storms produced strong winds of at least 45 to 50 MPH. There were several reports of winds in excess of 60 MPH however. Numerous trees were blown down and a few power poles snapped. Winds caused damage in the Poweshiek County with winds estemated at near 80 MPH.

A moist and unstable airmass was in place over Iowa. The airmass became uncapped by the early afternoon hours with CAPE values in the 1000 to 2000 J/kg range. Temperatures warmed to the low 80s by mid day with dew points in the low 60s. The soundings indicated a slight inverted V configuration. Isolated thunderstorms developed by the early afternoon hours. The storms produced some gusty winds and small hail. Storms continued to develop during the afternoon. The storms were pulse in nature with many of them only lasting about 30 minutes. A cluster of thunderstorms moved through central Iowa. A wet microbust occurred in Polk County with damage reported in the Polk City and Des Moines area. Near severe winds occurred at the Des Moines Airport with a 49 MPH wind gust. Power poles were downed in the Polk City area, with a few trees toppled in the Des Moines area. Gusty winds and nickel size hail was reported west of Redfield in Dallas County.

A major winter storm developed over the central U.S. as a strong upper level system move in on the southern jet stream. The system came through as a bowling ball type event as the upper low first became negatively tilted, then closed off over Iowa. Low pressure moved across Kansas into northern Missouri, then turned northeast across central into northeast Iowa as it intensified. The low dropped to about 978 mb as it moved through Iowa. The low brought a variety of weather to the state, with a blizzard over much of the west half of the state, and thunderstorms with pea to marble size hail over the east half. As the low passed to the east cold air and high winds overspread the state. Sustained winds of 30 to 40 MPH were widespread, with occasional gusts to between 50 to 60 MPH were common. Visibility in rural areas dropped to zero, remaining that way for an extended period of time. Heavy snowfall occurred over the western part of Iowa with snowfall rates approaching 4 inches per hour at times as the snow was convective in nature. A large area of Iowa northwest of a a Creston to Mason City line received in excess of 10 inches of snow. Some of the heavier totals include 18 inches at Estherville, 17 inches at Carroll, 16.8 inches in Estherville, 15.5. inches in Ringsted, and 14 inches in Pocahontas, Atlantic, and Goldfield. The combination of high winds, heavy snowfall, and the preexisting snow on the ground resulted in roads drifting shut quite rapidly. Widespread blizzard conditions resulted in numerous road closures over the northwest half of the state. Interstate 80 was closed westbound at Iowa City to the Nebraska border, and both east and westbound at Des Moines. Interstate 35 was close both north and southbound at Ankeny to the Minnesota border. Hundreds of people were stranded in their cars during the height of the blizzard. The National Guard was called out to conduct numerous SAR missions. Reports of 5 to 10 foot snow drifts were common across western and northern Iowa, with drifts of 16 feet reported in the Carroll area. The high winds and wet snow caused additional power outages over parts of the state as well. An additional 30,000 people lost power during the storm. Governor Chet Culver declared the remaining 39 counties of the state disaster areas, bringing all 99 counties under disaster declaration. In addition, a request was made to place 44 Iowa Counties into Federal Disaster Status. The request was granted, along with two additional counties. A total of 46 counties received a Presidential Disaster Declaration. The blizzard was considered the worst blizzard in decades for parts of western Iowa. In Carroll for example, the blizzard was the worst since the blizzard of 1947. During the storm in Des Moines, thunderstorms moved across the city. A woman was struck by lightning outside of Lovejoy Elementary School in Des Moines. She received minor injuries and reported pain in her arm following the strike.

A major winter storm affected Iowa through the 24th and 25th of February. A powerful upper low moved onto the west coast during the middle of the week, and advanced east through the Rockies during the end of the week. Strong warm air advection took place over the top of a shallow polar airmass that was in place over Iowa. The east-southeasterly flow at the surface drew cool and dry air into the state from the east, setting the stage for a significant ice storm. The main area of precipitation overspread the state during the early morning hours of the 24th and persisted through much of the 25th. Initially, very warm air aloft meant that the precipitation fell in the form of freezing rain and sleet. The central and northeast sections of the CWA were most effected with the ice as the southwest warmed to just above freezing. Ice accumulations ranged from around one quarter of an inch or so along a Carroll to Centerville line, to between one half and on inch over the northeast part of the CWA in the Waterloo, Tama, Marshalltown, to south of Mason City areas. Widespread tree and power line damage was reported across much of the northeast two thirds of the CWA. Reports of 345 KV lines down were received from Tama and Black Hawk Couties. During this time, easterly winds were blowing in the 20 to 40 MPH range, exacerbating the problem. Tama County reported 75 miles of power lines down. Butler County reported at least 250 power poles snapped already by the evening of the 24th. At the height of the storm, at least 265,000 customers were without power. Interstate Power and Light Company reported that 1000 miles of transmission line was down at one point and 2000 utility poles were snapped in their area covered by Alliant Energy. MidAmerica Energy reported 360 miles of transmission line down and 1600 utility poles snapped in their area. Final damage figures for the three utility entities involved in the ice storm were $70,000,000 damage to Alliant Energy equipment, $36,000,000 damage to MidAmerica Energy equipment, and $32,000,000 damage to Rural Electric Cooperative equipment. These figures are statewide figures and therefore were not entirely within the Des Moines CWA. The freezing rain changed over to sleet, and eventually snow late on the 24th into the 25th. Six to twelve inches of snow was common across much of Iowa northwest of a Bedford, to Des Moines, to Grundy Center line. Some of the heavier amounts include 11.5 inches at Algona in Kossuth County, and 10 inches at Dana in Greene County and Estherville in Emmet County. Along with the snow, many areas reported occasional visibility near zero in blowing snow on the night of the 24th into the 25th. Travel became very hazardous with many roads closed due to the combination of snow, blowing snow, fallen wires, and fallen trees. Numerous activities were canceled on the 25th as well. By the afternoon of the 25th, Iowa Governor Chet Culver had already given 60 counties the state disaster declaration by the afternoon following the storm. Subsequently, 46 of the counties, mostly in northeast Iowa, received a Presidential Disaster Declaration. Some of the hardest hit areas were in Poweshiek, Marshall, Tama, and Black Hawk Counties. Costs in the city of Waterloo, for example, were over $2,000,000 during the first week after the storm. This winter storm went into the books as one of the worst winter storms in many years. Although ice storms are not documented all that well, this storm appears to be the worst ice storm in Iowa in the past 40 years due to the large areal extent of the storm. Farther to the south and west the precipitation fell as rain. Enough rain fell to cause some minor flooding on the Chariton and Middle Rivers. The Middle River crested about a foot over flood state in Indianola, while the Chariton River crested a little over 2 feet over flood stage in Chariton.

A weak frontal boundary extending from northwest Minnesota into southwest Kansas advanced toward Iowa. The flow was very week, but the airmass was very moist. Precipitable water values were above 2 inches with a deep warm layer in place. The freezing level was between 14,500 and 15,500 feet. The CAPE in the -10 to -30 layer was significant at 800 J/kg, but in spite of that there was little hail due to the very high freezing level. Afternoon temperatures warmed in to the upper 80s to low 90s with dew points in the mid 70s. This pushed the most unstable CAPE to around 5500 J/kg. Lifted indices were in the -9 to -11 range by late afternoon. Tornadoes did not occur with a weak shear environment (under 20 kts) and with an LCL of 1000 to 1200 meters. There was a fair amount of DCAPE available, about 1500 J/kg. Thunderstorms formed in three areas as the afternoon progressed. One area was in northwest Iowa, with the second over eastern Nebraska moving into west central and southwest Iowa. The third area was smaller with development over the southeast counties of the state. Initially the storms produced some marginally severe half of three quarter to one inch in diameter. As the afternoon progressed, the two clusters in northwest and southwest Iowa merged, and the storms over the southeast weakened. The systems over the west took on more of a linear structure and the event transitioned into a wind event. There were several reports of trees and power lines downed by the high winds. The strongest winds was measured at 75 MPH in Adair.

The MCS that moved into Iowa during the morning hours weakened by the late morning hours. A wake low and pressure couplet developed on the north side of the decaying complex with a large area of 35 to 50 MPH winds. High winds were concentrated in a small area of central Iowa. Northern Dallas, northern Polk, much of Boone and all of Story Counties were affected. Winds in these areas were in the 40 MPH sustained range for an hour or so. Winds gusted to 67 MPH at the Ames Airport, with a 61 MPH wind gust reported at Kelly. In Polk County, a 59 MPH wind gust was reported at a schoolnet site in Grimes. Wind damage was limited except for in Story County. There were numerous reports of trees and power lines being downed by the winds. Along the southern edge of the high winds, a heat burst occurred at the end of the event. Temperatures warmed from the low to mid 70s, into the mid 80s to low 90s as the heat burst occurred during the early afternoon. The area of high winds spread east slowly with high winds reported to the east in Marshall, Tama, and Poweshiek Counties. A wind gust of 58 MPH recorded in Tama. As the high winds moved across Marshall County, 14 flatbed rail cars were derailed by the high winds from an elevated track 2 miles west-northwest of Le Grand in Marshall County.

Low pressure lifted northeast from the southwest U.S. in the upper atmosphere. A surface low formed and tracked east-northeast across northern Missouri into Illinois during the late afternoon and evening hours. Moisture with this system was quite limited with surface dew points holding in the 50s across southern Iowa. In spite of the limited moisture, with precipitable water values around one inch, thunderstorms fired during the evening hours. The wind profile was quite favorable for thunderstorm development, and freezing levels were relatively low, in the 11,000 to 12,000 foot range. The bulk of the severe weather was to the south of Iowa, however thunderstorms developed in south central into central Iowa during the evening. There were a few reports of high winds, but most of the storms produced hail. The severe storms produced three quarter inch to one inch diameter hail from the south central counties into the central counties. The most significant wind damage occurred in Jasper County around the Colfax area. High winds downed power poles in the area.

An intense low pressure moved southeast out of northern Alberta during the night of the 23rd and early morning of the 24th. The low tracked southeast across Lake Winnipeg early on the 24th and was over Lake Superior during the afternoon of the 24th. The low continued to move southeast during the late afternoon and evening. A deep trough of low pressure formed in the upper levels with a 140 kt jet streak passing over Iowa during the day on the 24th. A strong tropospheric fold was evident as the jet streak passed with stratospheric air extending well below 850 mb. Winds increased quite rapidly after sunrise with mid day winds sustained in the 40 to 45 MPH range over the CWA by mid day. Winds became quite gusty as well with most locations recording gusts of at least 50 to 55 mph. Several locations reported wind gusts in excess of 60 MPH. The strongest wind gust recorded was a 69 MPH wind gust at the Ames Airport in Story County. The strongest winds were in a band about 40 miles wide extending from Calhoun and Webster Counties on the northwest, southeast to Lucas, Marion, and Mahaska Counties on the southeast. Winds in this band gusted to 60 to 65 MPH for a one to two hour period. There as also a wind gust to 61 MPH in southwest Iowa in Union County, and a gust to 51 MPH in Cerro Gordo and Franklin Counties. Two people were injured in Des Moines by flying glass. High winds blew out a window broke out of the Polk County Human Resources Building. There were numerous reports of local power outages as branches took down power lines. Some accidents were caused by the high winds as drivers lost control of their vehicles. Spotty reports of trucks being overturned were also received. In Polk County, the mile long bridge over Saylorville Reservoir was closed for several hours due to the high wind.

As the low pressure system mentioned in the narrative above liftednortheast, a cold front swept through the state. In the wake of thefront, strong subsidence took place and very strong winds were mixeddown in the dry slot behind the front. Winds picked up to 35 to 45 MPHin most areas with scattered gusts in excess of 58 MPH. The strongestwind gust was recorded in central Iowa with a 65 MPH wind gust in Windsor Heights. Damage from the strong winds was limited by the fact that most of the leaves had fallen out of the trees. There were spotty reports of tree and power line damage caused by the high wind. The strong winds affected much of the Des Moines CWA with 39 counties reporting either wind gusts of 58 MPH or sustained winds of 40 MPH or higher.

A nearly stationary front extended east-southeast to west-northwest across Iowa. Cooler and drier air was to the north of the front, with very warm and unstable air to the south. Dew point temperatures approached 70 to the south of the boundary during the morning hours of the 8th. A short wave tracked southeast across the area in a general northwest flow. The air mass became quite unstable in the vicinity of the boundary with lifted indices around -7 C. The shear profile was favorable with about 40 kts of shear in the lower layers. Plenty of deep moisture was available with the system with precipitable water values in the 1.5 to 1.8 inch range. Hail was somewhat limited with the storms, but not absent with freezing levels in the 12,500 to 13,000 foot range. CAPE values ahead of the storms were in the 1500 to 2000 J/kg range, with CAPE in the -10 C to -30 C layer of the atmosphere in the 400 J/kg range. Thunderstorms which began well to the northwest during the previous night tracked southeast into Iowa during the morning of the 8th. A steady flow of moisture was transported into the area with a feed at 850 mb of about 25 kts. The storms were fast moving and the area tended to bow out. Wind damage was wide spread with numerous reports of winds of 60 to 70 MPH. An intense cluster of storms moved through the central Iowa area with measured wind gusts of 83 MPH reported at both Ames and Ankeny with the gust front passage. There was one reported tornado with the system in Ames. The tornado touched down near the power plant o nthe ISU Campus. Eight people were injured by the tornado. One was injured seriously enough to be taken to hospital. Initial damage estimates were around $150,000. Many of the storms produced hail, however much of the hail was below severe limits. Reports of penny size hail were received from several locations. The largest hail came with the cluster in central Iowa. Golf ball size hail fell west of Elkhart in Polk County. The storm and high winds resulted in power outages to 8700 customers in the Des Moines area. The high winds caused a semi-tractortrailer and a camper to oberturn on INterstate 80 just west of exit 141 in Polk County. The thunderstorms also produced locally heavy rainfall. Local flooding occurred on the north side of Indianola as the storms moved through.

A very dynamic synoptic situation was in place over the central U.S. during the day on the 29th. Warm and moist air was in place over Iowa with high temperatures for the day reaching the upper 80s to low 90s across the area. Surface dew point readings rose into the low to mid 70s by the early evening hours. This resulted in a very unstable airmass over the state with lifted indices in the -10 to -12 C. range and CAPE values in the 4500 to 5000 J/kg range. The airmass was quite warm with freezing levels in the 14000 to 15000 foot range. A closed upper low lifted northeast out of the central Rockies during the afternoon and evening. Surface low pressure lifted northeast across Nebraska, northeast into eastern North Dakota. A cold front trailing south from the low approached the state by the early evening hours. During the day, scattered convection broke out over the state. Clearing spread northeast as the upper level dry slot pushed northeast into the central U.S. Upper level winds increased in response to the approaching low with 500 Mb winds around 75 kts by the mid evening hours. Thunderstorms erupted quite rapidly during the early evening hours. Once initiation began, thunderstorms spread quickly in the unstable airmass. Mid level lapse rates were around 8 degrees C, which aided in thunderstorm development. With freezing levels quite high, hail was not a major factor with the storms. There were spotty reports of three quarter inch diameter hail to nickel size hail. Though hail was limited, a report indicated that hail fell hard enough in Warren County at mile post 44 along Interstate 35 that motorists were unable to see the road. The main mode of severe weather winds high wind. Reports of 60 to 75 MPH winds were very numerous. The highest winds recorded was in Union County west of Thayer with a measured gust of 81 MPH. Numerous trees were downed by the storms with power outages reported around the state. High winds destroyed a 40 x 80 foot storage building west of Manning in Crawford County. Another storm a camper in Boone County at Boxholm. In Hamilton County a semi-tractortrailer truck was blown over at the Flying J Truck Stop in Stanhope. Scattered reports of barns and grain bins being destroyed by the high winds were received. In Jasper County, some of the stronger winds occurred as the storm pass through areas east of Baxter. Winds of around 85 MPH blew down numerous trees. blew down an anchored corn crib, a machine shed, and blew hard enough to blow an air conditioning unit through the window into a house.

An unstable airmass was in place over the central U.S. on the afternoon of the 20th. A large area of high pressure aloft was located over the west half of the country, placing Iowa in a large scale northwest flow pattern. A weak cold front dropped southeast through the Dakotas and approached northwest Iowa. At the same time, a series of MCS's developed over the Rockies, and rode around the upper level ridge of high pressure. During the day, the dew points across Iowa warmed into the mid 60s to mid 70s with surface temperatures in the mid to upper 80s. The lifted index by evening was in the -5 C. range with CAPE values in the 2000 to 3000 J/kg range. The provided a rich environment for an MCS that approached the state during the later part of the afternoon. The MCS developed over eastern Wyoming and southwest South Dakota earlier in the day. As it overtopped the upper ridge, it turned southeast into Iowa. As it did, the storms took on more of a bow echo appearance and the cluster became a small Derecho. Early on in the event a tornado touched down briefly in Emmet County north of Gruver. It was in open fields and caused little damage. The main mode of severe weather was in the form of high winds. There were few hail reports, however with the freezing level above 16,500 feet, hail was limited. The winds caused widespread damage from Emmet County, east to Winnebago County, then south into the central part of the state about as far south as Interstate 80. South of this area no damage was reported as the storms weakened rapidly. Two semi-tractortrailer trucks were overturned in Story County by the high wind about 2 miles west of Nevada. There was one injury from this. One of the drivers had to be rescued as he hung over the edge of a bridge. He was taken to hospital, treated, and released. There were numerous reports of tree and power line damage over the northwest, north central, and central counties of the state. High winds blew windows out of a home at the ISU Agronomy Farm. Structural damage was reported in Marshall County at State Center. The roof of a large building with a roof of less than two years of age received damage. A high school roof in Story County at Nevada had its roof partially peeled back as well. In addition to these reports, there were scattered reports of outbuildings and sheds being flattened by the wind. Visibility during the high winds was occasionally reduced to near zero in blowing dust by the time the storms reached central Iowa. The gust front from the storms had moved well ahead of the storms themselves, some 10 to 15 miles ahead, with some of the areas receiving severe winds not receiving any rainfall at all.

A volatile situation took shape during the afternoon of the 10th. A unseasonably deep upper low had formed aloft over the southwest U.S., while at the same time a cold front dropped south across the state during the day. Behind the cold front was a strong polar high pressure area. The southwest flow aloft impinged on the frontal boundary, setting the stage for very strong thunderstorm development. Temperatures reached the low 90s over far southwest Iowa, with mid 80s over the central sections. Dew points reached the mid 60s to the south of the front by late afternoon. North of the front, temperatures were in the 50s during the afternoon. The very unstable air was lifted north over the frontal boundary with explosive development during the early evening as the low level jet began to strengthen. The airmass to the south was very unstable with lifted indices of -11 C., CAPE values of 3500 J/kg, and a freezing level of only 13,300 feet. Hail was very widespread with the event. During the initial convection, a super-cell moved into southwest Iowa. This storm dropped three small tornadoes in Audubon County. All of the tornadoes were relatively short lived and caused little damage as they were in open areas. The main weather feature was the hail. There were numerous reports of nickel to quarter size hail with the storms. Th largest hail occurred with the super cell in Audubon County, with tennis ball size hail falling southwest of Audubon. In several reports of hail of ping pong to golf ball size were received from Carroll and Guthrie Counties. As the evening progressed, a secondary line of storms formed to the north of the developing MCS. These formed in an east to west line across northern Iowa, producing a round of hail there. Late in the storm life cycle, a few of the storms began to produce strong winds. As one of the storms moved through the Des Moines area, winds of 57 MPH were measured. Some minor damage occurred to a fast food sign. Sixty MPH winds were reported in Marion County, while 60 to 65 MPH winds blew down power line poles in Poweshiek County. Late in the event, as the storms moved through Hamilton County, lightening struck a storage and repair shop building in Webster City. The building was set ablaze and was a total loss.

Low pressure dropped southeast out of the Canadian Prairie Provinces and into the lower Great Lakes. The low itself was not all that deep, about 1005 mb, however there was very strong dynamics associated with it. At 500 mb, a strong short wave dived southeast into the central U.S. on a 110 kt jet. As the low passed and a 1044 mb Arctic high pressure area built into the area, strong winds overspread Iowa from the west. Sustained winds of 40 to 45 MPH were common over nearly all of Iowa, with gusts in the 55 to 65 MPH range. The winds caused considerable blowing and drifting snow over the northeast counties. Damage due to the wind was minimal for the most part. The ground being frozen as well as the leaves being off the trees was helpful. There were scattered power outages due to fallen limbs, but little significant damage.

A cold front advanced across the plains and moved into Iowa during the night of the 6th. The weather situation was quite dynamic for early September. A low level jet of 50 kts developed ahead of the cold front. Warm air moved in at 500 mb during the day, which reduced the lapse rate significantly. There was a lot of CAPE, shear, and helicity in the lowest one to two kilometers of the surface, but parameters were weak above that. This lead to a mini supercell event. CAPE values were around 1500 J/kg and lifted indices in the -4 to -5 C. range. The freezing level was quite high and was in the 15,000 to 15,500 foot range. A line of thunderstorms that had persisted through the day ahead of the cold front strengthened during the mid and late afternoon hours before pushing east across Iowa. There was very little in the way of wind with this event with only an isolated event reported in Story County, and no hail reported. High winds caused tree damage in the Lacona area of Warren County. The winds were along the track of a tornado that touched down in Lucas County, however there was no evidence that the tornado was on the ground in Warren County. Several small tornadoes occurred over northwest into central Iowa. Most of them were brief touchdowns in open area, resulting in little damage. One of the tornadoes was on the ground for about 2 miles in Greene County. The tornado damages garages, porches, and trees for the most part. Several power lines were taken down as well. A second tornado in Greene County caused minor house damage west of Jefferson. Another stronger tornado touched down southeast of Collins in Story County. Four out buildings were damages or destroyed and numerous trees were taken down. This tornado was on the ground for nearly 3 miles as it headed northeast of Collins. The tornado lifted and another tornado formed in Marshall County shortly after the cell crossed the border. A tornado touched down in northwest Lucas County and tracked for 2 miles northeast. One farmstead had extensive damage with one machine shed destroyed and others damaged. Three other tornadoes occurred, One in Polk County east of Elkhart did minor damage. Another tornado touched down northwest of State Center and caused F1 damage along its 3 mike long track.

A very unstable airmass was located over Iowa on the 26th. Surface dew points rose into the mid to upper 70s along with surface temperatures near 90. Soundings indicated CAPE values around 5000 J/kg with lifted indices in the -9 C. range. The freezing level was relatively low, being a little over 12,000 feet. A steep lapse rate was in place with a 7 to 8 C. lapse rate between 850 and 500 mb. At the same time, a strong west to southwest jet in excess of 75 kts was in place over the central U.S. During the afternoon, a cold front dropped southeast into the state. Thunderstorms erupted during the late afternoon in advance of the cold front. The storms became severe very quickly and produced high winds and hail. There were a few tornadoes reported with the stronger storms. They touched down in open countryside and resulted in little damage. One tornado northwest of Maxwell in Story County tracked across the north end of a farmstead there. Several trees were downed and one window was blown out of the farm house. A tornado touched down in Marshall County south of Melbourne. The tornado may have actually been three separate tornadoes that developed and dissipated very rapidly. It was hard to distinguish if there were three, or if the damage path was produced by vortices rotating around the parent storm. There were three areas along the path of more noticeable damage. One was of F0 strength, the other two areas were F1 strength. The entire event took place in about 5 minutes. High winds and hail were widespread during the event. There was some very impressive hail reported. Very large hail of five and one half inches in diameter fell in Hancock County in the Kanawha area. Incredibly, three inch diameter hail fell in the same area about 30 minutes before the very large hail hit. The hail resulted in considerable vehicle and home damage in the area. There were reports of baseball size hail in Pocahontas County near Gilmore City. Reports from Sac County indicated two and one half inch diameter hail in the town of Odebolt. The hail did considerable damage in the city, including smashing out the windows in several homes and smashing car windshields. Most of the other hail reported around the state was golf ball and smaller size. Many of the storms produced high winds, resulting in a lot of tree and power line damage. Storms in central Iowa produced 60 to 75 MPH winds, resulting in many cars being blown off highways in central Iowa. Flash flooding occurred in Davis County as heavy rainfall of 3 to 4 inches fell on the already saturated county. This weather system was the third heavy rainfall to hit the county in as many days. County officials reported numerous roads closed to flowing water over the highways, even as sunrise approached.

Iowa remained in a northwest flow with numerous short waves embedded in the flow. A mid level cap was in place over southwest Iowa and areas southwest, limiting the formation of thunderstorms. The airmass was very unstable with lifted indices in the -12 C. range and CAPE values between 5000 and 6000 J/kg. Surface dew point readings were in the mid 70s well into the night. Thunderstorms erupted over northwest Iowa during the early morning hours. They became severe quite quickly and tracked southeast across the state. The storms produced hail of up to golf ball size in Greene County as well as Boone County. As the storms progressed southeast, they began to become wind producers. Wind gusts around 60 MPH were reported in parts of central and southeast Iowa with spotty tree and power line damage occurring.

A cold front moved southeast slowly southeast across Iowa during the day on the 17th. The surface front moved about half way through the state, while the front at 850 mb remained over the northwest part of the state. The airmass was unstable, but not extremely unstable. Lifted indices were around -2 to -5 C during the afternoon. The convective inhibition had dropped to zero by mid afternoon with CAPE values around 1500 J/kg. Thunderstorms erupted in the vicinity to just north of the surface cold front by late afternoon. An MCS developed over southwest Iowa and tracked east across the state during the late afternoon and evening. The main severe weather mode from this system was hail. There were numerous reports of three quarter to one inch diameter hail during the period. Some of the larger hail reached golf ball to baseball in size. The largest hail fell in Madison County in the Winterset area as baseball size hail pummeled the area twice. A few storms produced high winds. One of the stronger storms was over Adams County. In what appeared to be a macroburst, winds of around 60 MPH downed power poles and a few outbuildings east of the Corning area. The power poles were set on fire as they fell. Later in the evening, over Monroe and Mahaska Counties, a thunderstorm turned into a bow echo segment and caused considerable damage near the Eddyville area. One mile east of Eddyville on 340th St. along the Wapello-Mahaska county line was the hardest hit area. Two farmstead received extensive damage around 9:15 p.m. A microburst likely occurred on the farmstead located along the north side of the road (western-most farmstead), followed by a damage path spreading one-quarter mile east-southeast to a farmstead along the south side of the road. At the southern farmstead, two farm outbuildings were destroyed. Three poles rooted five feet into the ground were lifted complete out of the ground. The roof of a shed was peeled back. Pieces of the outbuildings from the northern farmstead spread out to the east and southeast up to 150 yards in width near the southern farmstead. Length of the visible damage path was around ½ mile. Persons in both farmsteads reported the duration of the strongest winds to be from 20 to 30 seconds. Maximum winds were estimated to be around 85 mph. When all was said and done, high winds flattened a barn and several outbuildings, silos, and trees. Boards from the barn were driven through a car east of Eddyville along the southern Mahaska County border. Several roads were blocked by fallen trees throughout the area. Several hogs were killed when one of the barns collapsed near Eddyville.

An intense low pressure moved across the northern tier of states during the day on the 27th. Very strong south-southwest winds developed with profilers indicating wind of 50 to 65 kts within the lowest range gates. Temperatures warmed into the mid 80s to low 90s with the atmosphere becoming adiabatic to between 750 and 600 mb, allowing for strong mixing down to the surface. Winds increased during the day and reached high wind criteria by the early afternoon. Most of the state saw sustained winds of 40 MPH or higher. Several locations gusting to between 60 and 65 MPH. The winds also produced blowing dust around the state. Isolated reports of visibility reduced to near zero were received. Spotty damage occurred around the state. An 18 inch tree limb broke off and fell through the roof of a house in Windsor Heights. A two to three foot diameter tree was snapped off at the base in Ames. There were numerous reports of power outages caused by downed tree limbs. In Union County, a 200 X 40 foot chicken house had the roof blown off. There were several head of cattle in addition to the chickens contained therein trapped in the debris.

A warm front lifted north across the state during the previous night. At the same time, intense low pressure formed to the west of Iowa and tracked northeast through South Dakota into Minnesota. The low intensified as a negatively tilted upper level trough of low pressure in the upper atmosphere lifted northeast out of the southwest U.S. A strong jet and pronounced dry slot was evident in the warm sector of the system. The jet and dry slot tracked across Iowa during the afternoon and evening of the 18th. This set the stage for the high wind event. A very strong south to southwest flow developed over the state. Profiler data showed wind of 50 kts at 500 meters during much of the morning into the early part of the afternoon. The winds increased to 75 kts at the 500 meter level by the late afternoon and evening hours. The strong winds in the lowest range gates were not realized during much of the day do to strong upward vertical velocities. Strong subsidence developed during the late afternoon and evening hours, allowing for sufficient mixing and for the strong winds to be realized at the surface. During the day, winds were in the 30 to 35 MPH range across the state, with frequent gusts to around 55 MPH. During the late afternoon and early evening hours, winds increased with sustained winds of 40 MPH or more across most of the state, with many areas reporting gusts of 60 to 65 MPH. Widespread light damage was reported over the area, with scattered reports of significant wind damage. Several reports of tree, power line, and out building damage were received from around the state. Reports of semi-tractortrailers being blown off the roads. U.S. Highway 18 in Cerro Gordo County was closed by two overturned trucks that were blown over by the wind. Also, traffic was rerouted in Warren County at the junction of U.S. Highway 65-69 due to a truck being blown over. In addition to the wind damage problems, dry conditions around the state lead to areas of blowing dust. Visibilities were restricted at times, especially over the west half of the state. In Kossuth County, the visibility dropped to as low as three eigths of a mile at the Algona Airport for about an hour.

An intensifying low pressure system moved southeast across southern Minnesota into the lower Great Lakes. As the storm passed Iowa, strong subsidence took place. A tropospheric fold reached below 700 mb in the wake of the storm, enhancing the wind. Strong winds were sustained above 40 MPH for several hours over much of the state for a period of a few hours. Several locations reported gusts of 50 to over 60 MPH. Trees were damaged over a large part of the state as well. Some of the higher winds reported were 64 MPH at Glidden in Carroll County as well as at Rockwell City in Calhoun County. Winds at the WFO in Johnston gusted to 63 MPH. Sixty two MPH winds were reported at Farnhamville in Calhoun County as well as in Prairie City in Jasper County. There were too many locations to list here with winds of 58 to 61 MPH. Significant damage occurred in West Des Moines. Two full roofs and one partial roof off commercial buildings in the Valley Junction district of West Des Moines. Property damage estimated at up to $250,000. Numerous reports of power lines down, tree damage and power outages (at least 9000 customers without power in Des Moines. Johnston, a suburb of Des Moines also lost power). Overall, MidAmerica Energy reported that at one point they had 20,000 customers without electricity. Two reports of semi-trucks overturned, but unsure if these are weather related. In north central Iowa, a semi-tractortrailer was overturned near the town of Thornton. The driver received minor injuries and was taken to hospital, treated, and released. In Polk County, a 74 year old Des Moines woman was injured when the wind pulled her out of her house as she was exiting. She suffered shoulder and leg injuries. They were minor and she was treated and released.

Once again strong convection affected Iowa during the overnight hours. A forward propagating MCS developed over the High Plains of western Nebraska into western South Dakota. The MCS advanced east through the night. During the early predawn hours, thunderstorms developed along the upper air warm front extending from north of Des Moines toward Sioux City. Very heavy rainfall of 2 to 5 inches occurred along this line, though little in the way of severe weather occurred with it. There was one storm that developed further south and dropped one inch diameter hail north of Vail in Crawford County. Shortly before sunrise, the lead bow echo from the MCS entered the DMX CWA. As it did, it produced pea to marble size hail and 30 to 50 MPH winds at most locations. High winds of 60 to 70 MPH were reported in a few locations, causing damage in the form of blown down trees and power line damage. Winds in the Grand Junction area of Greene County knocked out windows in a house there. As the winds moved into the Ogden area of Boone County, several trees were downed on a farmstead there. Two cars were destroyed, a 1992 Chevrolet pickup and a mid 1980s Dodge.

A very moist and unstable airmass was in place over Iowa. South winds at the surface into the mid levels drew precipitable water values were in excess of 50 mm over the CWA with 850 mb dew point values reported at +19 degrees C. A cold front held nearly stationary during the previous few nights to the northwest of Iowa. The front began to move southeast during the day on the 25th, and moved across the state during the evening hours. Thunderstorms from the previous nights convection north and west of Iowa moved into the state during the morning hours. As temperatures warmed during the morning hours, the atmosphere became very unstable. Temperatures rose into the 80s quickly over central Iowa with dew points at the surface in the low to mid 70s. During the afternoon, temperatures in eastern Iowa rose into the mid 90s. With CAPE values over 3000 J/kg and Lifted Indices around -8 C., the thunderstorms re-intensified rapidly. The initial line of thunderstorms produced scattered severe weather in parts of central and eastern Iowa. There were few reports of any hail as the freezing level was 15,100 feet. Gusty winds were common with the stronger storms producing severe winds. Winds as high as 65 MPH were reported in the Hudson area of Black Hawk County. Roof damage was reported on a farm southeast of Hudson. Trees and power lines were damaged in the Tama area by 60 MPH winds. By early afternoon, a second line of thunderstorms developed in western Iowa along the cold front. In similar fashion to the earlier storms to the east, the second line of thunderstorms produced high winds. The high winds were scattered in nature with most damage limited to trees and power lines. Winds broke windows of a house south of Delphos in Ringgold County. As the thunderstorms moved through Central Iowa, lightning struck the National Weather Service office in Johnston. The office took a direct strike with damage reported to some of the equipment in the office. Heavy rainfall was associated with many of the thunderstorms. Rainfall 3 to 5 inches fell in a 2 hour period over Marion County. In the Melcher-Dallas area, 5.26 inches of rain was recorded. The heavy rainfall caused some flash flooding. Being as antecedent conditions were very dry, the flooding was minor and limited to agricultural areas and low rural roads. A few county roads were closed for a brief period of time due to the flooding. As the storms moved through Jasper County, lightning struck a garage and set it on fire. The fire was contained quickly by the volunteer fire department.

An intense late May low pressure dropped southeast across northern Minnesota into southern Wisconsin during the afternoon hours. The low took on the characteristics of an Alberta Clipper as it dropped to around 993 mb during the afternoon hours. A strong surge of warm air pushed into Iowa, sending the mercury into the upper 80s to low 90s. A cold front pushed southeast into the state during the mid afternoon hours. The atmosphere was too dry for any thunderstorm development. Strong winds aloft were brought to the surface as the atmosphere became super adiabatic under strong cold air advection behind the front. Winds were sustained in the 30 to 45 MPH range for several hours during the late afternoon, with gusts to between 40 and 60 MPH. The highest recorded wind speed came from the Boone area with a 58 MPH wind gust. Numerous reporting sites had wind gusts over 50 MPH. Scattered damage was reported with tree limbs and some power lines being taken down. Several power poles were blown down by the wind in Wright County. Another problem was with blowing dust. Visibilities were reduced significantly causing traffic slow downs. In a few areas motorists were required to turn on the headlights. One fatality occurred from the wind event. A family was camping at a campground 5 miles southeast of Oskaloosa. Three people were in a tent when an 80 foot tree, weakened by high winds during the previous 18 hours, fell on the tent at approximately 0425 on the morning of the 31st. A 23 year old female was killed instantly. The other two occupants were uninjured.

A very unstable air mass was located over Iowa during the afternoon of the 18th. Low pressure moved across the northern U.S. with a trailing cold front extending south from the low. A warm front had lifted north into Iowa during the afternoon. Temperatures warmed well into the 80s over the south half of Iowa, with surface dew point temperatures in the upper 60s to low 70s. This produced lifted indices of -5 C. and below. During the late afternoon thunderstorms erupted east of the approaching cold front. A line of thunderstorms developed rapidly and produced numerous reports of hail ranging from three-quarters of an inch up to golf ball in size. The line progressed east into central and eventually eastern Iowa before it weakened. The system began to become more of a wind system after sunset. Wind gusts of 60 MPH were reported in south central into parts of central Iowa. The most significant damage occurred in Marion County where high winds downed power pols west of Attica.

A nearly stationary front extended east to west across Iowa during the afternoon of the 22nd. The airmass was primed with dew point temperatures in the mid 70s south of the front and precipitable water values around 2 inches. Thunderstorms erupted during the early evening hours over Nebraska and advanced east into Iowa along the front. The storms were generally speaking now severe. Gusty winds and heavy rain was produced by most of them. Just as the storms approached central Iowa, a bow echo beta element formed in Dallas County. The bow echo tracked east into Polk County. Heavy wind damage occurred in eastern Dallas and Polk Counties. Winds gusted as high as 80 MPH as the storm roared through Des Moines. At one point, near 50,000 customers were without electricity in the metro Des Moines area. By the evening of the 23rd, power was restored to all but 13,000 to 15,000 customers. Some of the harder hit areas were without power for 2 to 3 days. Damage to trees and power lines was extensive. There were several reports of semi-tractortrailer trucks being blown over by the high winds and structural damage occurred to a few homes. Just before the storm moved into the metro Des Moines area, a very distinct funnel cloud was visible. The funnel cloud persisted for about 15 minutes, but did not come closer than about 40% of the way to the ground. The Des Moines public schools were closed for the day in what was the first time in the history of the city that schools were closed due to severe thunderstorm damage. The severe weather ended about as quickly as it began. After passing through Des Moines, the bow echo lost its character. In addition to the severe weather, flash flooding was a problem. The storms produced very heavy rainfall of in some cases nearly 2 inches in 20 minutes. Highways were under water in Dallas and Audubon Counties. Evacuations were considered for the town of Brayton in Audubon County, and Highway 144 was impassible in Perry.

The airmass over Iowa was quite unstable during the predawn hours of the 10th with surface dew points in the 70s. In spite of the fact that a weak cold front had passed through the state, little drying of the atmosphere took place. An unseasonably strong upper level closed low pressure system moved southeast across North Dakota into west central Minnesota during the morning hours of the 10th. Several lines of thunderstorms formed over southeast South Dakota into northwest Iowa and moved southeast from there. The storms produced very heavy rainfall during the initial round of storms along with winds of 40 to 50 MPH. The thunderstorms formed into a well developed MCS by dawn with the second round of storms forming into a bow echo. Very high winds pushed from west central into central and parts of south central Iowa as the bow echo pushed southeast. Numerous reports of 60 to 70 MPH winds were received. Carroll County was especially hard hit with a 96 MPH wind gust recorded in Glidden. Carroll and Crawford Counties were the most heavily impacted. There were approximately 140 electrical transmission poles down in about a 4 mile stretch 2 miles north of Carroll and to the west. The loss of these lines disrupted large portions of western Carroll County, and eastern Crawford County. Newspaper reports received in early August indicated damage to the transmission lines at $1,500,000. The strongest winds, those exceeding 70 MPH, extended into Guthrie County. Winds in the Panora area topped out at 77 MPH. Extensive damage was reported to grain bins. One of the largest was in Guthrie County, where a 300,000 bushel bin was collapsed on one side by the winds. Crop damage in the area was into the millions of dollars. Survey results indicated that nearly 25% of the corn crop in Carroll County was totally flattened. Damage surveys also indicated very extensive crop damage on either side of Carroll County, in Crawford and Guthrie Counties as well as the north half of Audubon County. Governor Vilsack declared Carroll and Crawford Counties disaster areas. Early reports indicated damage to 70 to 80 percent of farm fields in both counties. Although no injuries were reported, high winds overturned a semi-tractortrailer truck in Madison County west of Winterset. The bow echo continued to move south-southeast across south central Iowa. The Lorimor area of Union County was hard hit. Tree Limbs and Power Lines down in Lorimor with 3 residences receiving minor damages from tree limbs. Two cars, a pickup, and camper were damaged by tree limbs in Lorimor. In rural Lorimor the top half of a large barn was gone along with the hay stored inside. Steel grain bins were damaged by flying debris and trees, and machinery was damage by sections of the building debris.

The weather pattern was very similar to the previous day. Temperatures were close to 90 F. by early afternoon with surface dew point tempertures in the low to mid 70s. Thunderstorms developed in the weak flow environment rapidly. Though the initial storms were not severe and were heavy rain producers, numerous outflow boundaries resulted from the storms. A few of the storms became severe along the outflow boundaries of pre existing storms. Wind and hail damage occurred in Polk County southeast of Altoona from one of these storms. The downburst winds damaged crops, trees, and downed power lines. Another storm produced a strong downburst south of Winterset in Madison county. Several small trees were damaged and doors were ripped off of sheds and several grain bins were thrown. Downburst winds in Mahaska County caused a 6 miles stretch of damage along U.S. Highway 63 east of New Sharon. Numerous large branches were downed, crops were flattened, and a few large trees were downed. The width of the damage path ranged from a few tens of meters to nearly a kilometer wide.

A weak cold front moved southeast across Iowa during the afternoon of the 26th. The airmass was quite capped and thunderstorm development was limited. CAPE values by mid to late afternoon reached 3000 to 3500 J/kg just ahead of the front. Surface temperatures topped out around 90, with dew point readings in the low to mid 70s. Thunderstorms erupted just ahead of the front, but the line of storms was scattered to broken at best. For the most part, the storms produced hail around an inch in diameter. There were two reports of golf ball size hail from one cell as it moved through the Mitchellville area of Polk County. There were reports of high wind from a few of the cells in southwest Iowa. Trees were blown down by 60 MPH winds west of Lenox. The scattered line of thunderstorms produced winds of 60 to 70 MPH. The greatest damage reported came from Union County in the city of Kent. High winds damaged part of the front of a brick building and tore off a large barn door. Most of the other wind damage was limited to downed trees and power lines. One tornado touched down briefly in Tama County. The tornado reportedly only touched the ground and caused no damage.

A strong southerly flow was well established over the central U.S. Temperatures pushed well into the 80s during the afternoon. Surface dew point temperatures rose into the mid 60s to low 70s across the state. Initially, the atmosphere was capped. By the late afternoon hours the cap broke as the cold front pushed into the state from the northwest. Thunderstorms developed rapidly into a scattered to broken line. Hail was widespread with the storms with sizes ranging up to 2 inches in diameter. Two inch hail was reported at Brooklyn in Poweshiek County as well as southwest of Bedford in Taylor County. There were numerous reports of golf ball size hail with the storms. Windows were shattered with some of the larger hail with a few reports of damage to vinyl siding on houses. A few of the storms produced high winds. Winds of 65 MPH were reported in Hardin County south of Hubbard. Winds were around 80 MPH in Madison County, toppling power poles. There were several tornadoes with the squall line. The first tornadoes touched down in the northeast part of the state. They did not cause much damage as one touched down briefly in Hardin County, another in Grundy County. A short time later a tornado made a brief touch down north of Altoona in Polk County. Another tornado touched down between Bondurant and Elkhart. This tornado was the strongest of the afternoon and tracked southeast toward the Mitchellville area. Damage was reported to power lines and out buildings along the path. Fortunately the track did not move through a populated area. The last tornado touched down near the Waterloo area southwest of Eagle Center. This was also a brief touch down.

Intense low pressure located northeast of Iowa, combined with high pressure building into the area produced a very strong pressure gradient across the state. The low pressure deepened to below 990 mb as it approached Lake Superior during the afternoon. Winds gusted to over 50 MPH in most places throughout the day on the 9th. A few locations reported winds gusting in excess of 60 MPH. Several reporting sites in the CWA had sustained winds of 40 MPH or more for a period of a few hours during the day as the low intensified. Scattered damage was reported around the state along with spotty power outages. For the most part, damage was limited to trees and some roof damage to out buildings. Though not major, the damage was quite widespread.

As the storm system mentioned above lifted out of the southern Plains a line of thunderstorms formed near the strong frontal boundary. Strong divergence aloft combined with increasing instability resulted in rapid development of linear thunderstorms. Several bow elements were embedded in the line as well. Most of the storms produced hail, and in some cases enough to cover the ground. The hail was small with mostly pea size being reported. High were were the main feature with the storms. Numerous reports of 60 to 80 MPH winds were received. Structural damage was reported with some of the storms. For example, high winds destroyed grain bins on one farm in Cass County at Massena. In Ringgold County, the storms damaged garage doors and walls and blew several animal shelters away. As the storms moved into Clarke County, high winds struck a rural home south of Hopeville. One man was caught outside and was lifted by the winds and thrown into the porch. He was hospitalized with 5 broken ribs. In Marshall County, corn cribs were blown away south of Marshalltown and the roof was ripped off of a house in Le Grand. Several reports of trees and power line being downed were received across the south half of the state. The storms spread northeast toward the end of the event with winds around 70 MPH pushing northeast as far as Bremer County. Plainfield reported wind damage as 70 MPH winds swept through the city around 0100. Some of the worst damage occurred in Jasper County in the town of Lambs Grove. A microburst formed at the apex of a small bow echo. Winds tore through the area with speeds near 100 MPH. Six houses sustained severe damage and several other buildings in the area were destroyed by the high winds. Countless trees were downed in the area as well. Damage was similar to that of an F1 tornado. Damage was in the millions of dollars in the community. One homestead sustained $500,000 damage as a 40 by 70 foot machine building and its contents were destroyed. Two people were injured from the storms. In Clarke County, two semi-tractortrailer rigs were overturned as the gust front hit the area. One of the drivers sustained minor injuries. In Warren County, high winds overturned a semi-tractortrailer rig on U.S. Highway 65 in Indianola. The driver of that rig also received minor injuries.

A strong upper level low pressure lifted northeast out of the southern Plains during the afternoon of the 6th. During the heating of the afternoon, thunderstorms erupted in the unstable air. The freezing level was around 15,000 feet, so hail was not a great threat. Surface dew point temperatures were in the upper 60s to low 70s with precipitable water values around 1.75 inches. Thunderstorms fired southwest of the Des Moines metropolitan area. A tornado touched down in rural Madison County. The tornado was about 60 feet wide and produced a half mile long path of damage in open country. As the storms moved northeast they continued to intensity. One cell dropped a tornado at the Glen Oaks Golf Course in West Des Moines, causing some minor damage there. The tornado tracked northeast and flipped a semi tractor-trailer truck in Interstate 35 resulting in one injury. It continued northeast and hit an apartment complex causing damage to the building and destroying an 8-car garage. The path was more intermittent as it continued northeast into the city. There were numerous reports of trees and power lines being downed. The tornado lifted as the event transitioned into a high wind event. The storms produced wind damage in Johnston as it moved through the area. High winds of 80 to 85 MPH occurred in northern Polk and southern Story Counties before they weakened. A grain bin was flattened, along with tree and crop damage, as the storm moved through the Elkhart area. Just northwest of that, in Slater, high winds took the roof off of a house in southern Story County. One person in the house was injured. The storms continued to track northeast, eventually dropping another tornado in Butler and Bremer Counties. The tornado had a somewhat intermittent track touching down south of Shell Rock and lifting northeast of Waverly. For the most part the tornado tracked through corn fields there. One farmstead was hit in Butler County. A grain bin was destroyed and blown one quarter of a mile across a field, another was blown off its foundation, a shed was destroyed, and crops were damaged. In Bremer County, one car and a garage were damaged along the tornadoes path. Another farmstead was hit north of Waverly. Part of a machine garage was destroyed and blown about 30 feet off of its foundation.

A hot and unstable airmass was in place once again over Iowa. Thought the sub-tropical ridge of high pressure was in place over the state, thunderstorms were able to break the cap during the late afternoon. Temperatures soared into the mid 90s to near 100 with dew point temperatures in the mid 70s to mid 80s. Lifted indices at the time were around -12 degrees C, with CAPE values in excess of 6500 J/kg. An outflow boundary was located east to west just north of the Des Moines metropolitan area. Thunderstorms erupted just north of the city during the late afternoon. Though isolated, the storms became severe quite quickly and produced high winds. There was some marble size hail, however with freezing levels near 15000 feet, hail was quite limited. Sixty five MPH winds swept into the town of Bondurant causing power line damage and downed trees. There were several waves of wind as cells developed rapidly in the same area as the entire area sank southeast around 5 MPH. Structural damage was reported in Bondurant as the last cell moved through. This cell produced winds around 80 MPH, damaging roofs in the area. One bar and grill in town sustained $85,000 in damage. A clearly defined funnel cloud was visible with the storm, however it did not touch down. As the storm moved southeast, 65 MPH winds were repotted in the Altoona area by a HAM radio operator with a hand held anemometer. The winds spread out into western Jasper County, causing crop damage in the area. Thunderstorms fired a little later in the afternoon near the town of Gilbert in Story County. The storms produced 60 MPH winds for a short period of time, however the storms weakened rapidly.

A very unstable situation unfolded during the afternoon of the 18th into the evening hours. Very warm and fairly moist air was drawn north into Iowa as the warm front that had been to the south of the state the previous two days lifted north of Iowa during the day on the 18th. Dew point temperatures were in the low to mid 60s over much of Iowa. In spite of the relatively low dew points, the airmass became quite unstable. CAPE values were in the 3000 to 4500 J/kg range by the early evening. A cold front entered the state during the late afternoon hours. Thunderstorms developed explosively along the cold frontal boundary by early evening. A nearly solid like of thunderstorms began to move east across the state. One tornado was reported in Carroll County south of the Glidden area. The touchdown was brief and occurred in open country. Much of the severe weather with this event was in the form of hail. Numerous locations reported hail anywhere from three quarter inch in diameter up to golf ball size. The largest hail report was received from Emmet County. Baseball size hail fell south of the Armstrong area, causing considerable damage to roofs and crops in the area. As the evening progressed, the storms produced more winds, in part due to the collapse of the line. high winds caused scattered power outages around the state. A wind gust in Worth County moved a livestock trailer, pushing the trailer sideways. The line of thunderstorms weakened rapidly as the midnight hour approached.

A very powerful storm system moved through the southern Rockies during the night of the 10th and early morning of the 11th. Intense surface low pressure formed over western Kansas with a central pressure by sunrise on the 11th of 977 Mb. The weather situation was very dynamic with 500 Mb winds over 100 kts and a very sharp dry punch clearly visible on the satellite pictures. During the day the warm front that extended east from the low reached into southern Iowa, then extended eastward. There were two things that occurred during the day. The first was a very strong supercell that formed over northern Missouri during the morning. This storm lifted north-northeast at about 50 kts into Iowa, producing a long track tornado with a path extending nearly all the way to Des Moines. During the afternoon the warm front surged north with the northeast progression of the surface dry line. Dew points rose into the mid 60s to the south of the warm front across much of the southeast half to two thirds of Iowa. Surface temperatures in these areas reached the 60s north, with 70s south. With the atmosphere primed, the dry line began to move into Iowa. Dew point temperatures behind the dry line were in the 30s with southwest winds of 30 to 50 MPH. A broken squall line formed on the nose of the dry punch and became severe quickly. The storm cells themselves were not all that large, but nearly every cell along the line did carry a mesoscale circulation. There were several tornado touchdowns as the line lifted north as well. The primary severe weather during this even was the tornadic nature of it. There were reports of wind and hail, but everything considered these reports were pretty scattered. There were very few reports of wind and hail with the first supercell as it lifted north out of Missouri. One inch diameter hail was reported in Ringgold County east of Redding. Reports of winds and hail were more frequent with the second line of thunderstorms. There were numerous reports of hail up to marble size with this line, however there were not all that many reports of hail larger than that. A few reports of three quarter to one inch diameter hail were received from Marion and Polk Counties. The most significant hail occurred in northeast Iowa in Butler County. Golf ball size hail fell in the town of Parkersburg as the line passed over the city. There were more reports of wind with the second round. Nearly all locations reported winds of at least 50 MPH as the line passed overhead. Scattered reports of winds of 70 to 85 MPH were received. Wind damage occurred in Boone County as high winds downed power lines and downed outbuildings north of Ogden. The greatest wind damage occurred over northeast Iowa in Black Hawk and Franklin Counties. A building was blown off of its foundation and onto an adjacent road southwest of Hampton in Franklin County. A roof of a barn was damaged and a grain wagon was tipped over northwest of Hampton. Roof and house damage was reported over parts of Black Hawk County as well. Five injuries occurred in Warren County at Carlisle when winds of around 65 MPH toppled a school bus. Twenty one children were on board the bus when it overturned with 5 treated for minor injuries. Spotty damage was reported around the greater Des Moines metropolitan area. Several tornadoes occurred with this system. The most significant tornado entered southern Iowa around mid day. This tornado reached minimal F3 intensity just east of Mt. Ayr (Ringgold County). Property damage is estimated at over $500,000 in Ringgold county alone. Across the Des Moines area of responsibility, at least 15 homes were destroyed, and 60 residences were damaged as around a dozen tornadoes touched down. A supercell thunderstorm moved north from Missouri into southern Iowa late in the morning of April 11. The storm produced a tornado in northern Missouri and crossed into Iowa in Ringgold County. The storm, and tornado, moved north through Ringgold County with a continuous damage path half way through the county. The damage path continued north through northern Ringgold County, southeast Union County and into northwest Clarke County. In this area, the path was not continuous. Based on damage reports, the tornado continued to produce occasional damage in Madison County. Chaser reports indicate the tornado had a multi-vortex structure as it moved through Ringgold and Union Counties. The last reported sighting was in northern Polk County where a brief touchdown was reported with no damage. The storm likely produced one tornado from the Missouri border to Madison County with an intermittent damage track. Damage in Ringgold County was severe with initial estimates around $1 million. The county was later declared a federal disaster area by President Bush. A second tornado briefly touched down in northern Polk County. The touchdown in Polk County was indeed a separate tornado. Even though the tornado was from the same parent cell, the system had occluded and was in the process of forming a new tornado as it passed over the western part of the Des Moines area. Reports from this tornado indicate that at least 9 homes were damaged or destroyed, one business destroyed, and a school building damaged. In addition to losses to homes, one farmstead was hit with considerable damage and some livestock damage. A series of tornadoes formed on the heels of the supercell tornado as the dry line pushed into the state. Most of these were brief touchdowns, however the storms were moving around 60 MPH. Three tornadoes touched down in Boone County. The most significant tornado touched down north of Ogden. It produced a 3 mile long track up to 1/8 mile wide. Farm site hit along highway P70. Barn and grain bins destroyed, knocking out windows in house. Otherwise only minor damage to house. Debris scattered 1 mile to next farm site where there was minor damage to many buildings. Track continued north-northeast across highway E26 into the campground at Don Williams Lake. A storage building was destroyed, several trees downed, plus outhouses, picnic tables and signs were damaged. The damage track dissipated on the northeast side of the Don Williams Recreation Area. There were several brief touchdowns with relatively minor damage in Guthrie, Greene, and Hamilton Counties. A stronger tornado touched down in southeast Black Hawk County, causing significant damage to two homes in the La Porte City area. The most serious tornado in terms of loss of life occurred in Wapello County. A tornado developed in rural southern Wapello County, a mile southwest of Agency, Iowa, around 1600 CDT, on Wednesday, April 11. The tornado path was 50 to 100 yards wide with sporadic touchdowns toward the north-northeast for the next 6 miles. Survey responses indicated that the duration of impact at any one location was only 15 to 30 seconds as the tornado quickly moved through Agency and over farms at a 60 mph horizontal movement. The Odd Fellows Lodge in Agency was destroyed, and over 50 residences were damaged. Two women inside were killed, three people injured and three people had no injuries. As the storm moved through Agency, a garage was lifted and carried about 100 meters off of its foundation. The car inside was twisted and covered with debris. In another incident, one house was hit by the tornado causing damage to the house. The family dog was in the dog pen at the time. The tornado lifted the pen and twirled it through the air. The dog pen was deposited some distance downstream and what was truly amazing was the fact that the dog was uninjured. Following the tornado, U.S. Highway 34 was closed for 2 hours in order to removed debris from the highway. Governor Tom Vilsack visited the area during a storm survey. The governor spoke with Brenda Brock of the National Weather Service, Ellen Gordon, Administrator, Iowa Emergency Management Division, emergency management personnel (fire department, law enforcement, mayor) and the public. A proclamation for emergency disaster assistance was signed.

Following the passage of the powerful storm system earlier in the weekend, another round of severe weather was on tap for the state. The cold front from the previous storm did not move all that far to the south of Iowa. As a result, warm and moist air was able to move north into Iowa rapidly. A warm front lifted into southern Iowa during the late afternoon hours, sending temperatures into the 80s over parts of southern Iowa. Dew point temperatures jumped into the low to mid 60s. The atmosphere became very unstable with thunderstorms developing along the front. Most of the storms were associated with the warm front itself, though a mesoscale feature moved along the front setting the stage for an additional like of thunderstorms that developed north to south in south central Iowa. The main feature with the storms was hail. There were numerous reports of hail ranging from nickel size up to golf ball size. Several of the storms had well developed meso circulations associated with them. A few tornadoes resulted. Two of the tornadoes were very small and only touched down briefly in Tama and Dallas Counties. The other tornadoes were stronger. One tornado touched down in Decatur County near Leon. Two people were injured, one requiring hospitalization, as a mobile home was overturned by the gust front ahead of the storm itself. The second of the stronger tornadoes moved through Adams County. A trailer house was overturned and the roofs were removed from two sheds on a farm northeast of Mt. Etna. Thunderstorms produced very heavy rainfall of one to two inches per hour over Ringgold County. Total rainfall approached 4 inches in less than 3 hours as storms repeatedly moved across the same areas. The rain caused flash flooding in the county. In one instance, Lotts Creek overtopped a road southeast of Mt. Ayr, causing nearly $50,000 in damage as the road washed out. As the storms moved through Decatur County, lightning stuck a house in Garde Grove. The house was set on fire, but it was not detected for several hours after the lightning strike. The house was destroyed and completely burned to the ground.

A powerful storm system lifted northeast out of the Rockies during the night of the 6th into the morning of the 7th. The storm intensified rapidly as it moved across the central U.S. with the central pressure falling below 980 Mb during the day on the 7th. A very strong pressure gradient resulted. Winds increased during the predawn hours of the 7th as the gradient tightened and the dry slot moved over the state. Winds gusted to as much as 61 MPH by shortly after 0400 CST in Carroll. During the day on the 7th, sustained winds increased to 35 to 45 MPH across the state by shortly after sunrise. The winds caused at least minor damage in most areas of the state. There were numerous reports of tree limb damage and objects being blown around. The strongest winds were over the north and west portion of the Des Moines CWA. A few of the wind gusts include an 83 MPH wind gust near Mason City. At one point reports indicated winds were sustained at 55 MPH with gusts to 83 MPH. Trees were toppled, street signs were blown down, and shingles were removed from many buildings. Several semi-tractortrailer trucks were blown over on Interstate 35 by the storm force west wind. An official wind gust of 82 MPH was received from Storm Lake, just outside of the Des Moines CWA. Eighty MPH winds were reported in Emmet County at Wallingford. One to two foot diameter trees were uprooted. In addition, roof damage was reported as well as numerous reports of grain bins being blown over. In Wright County, 74 MPH winds were recorded at the Eagle Grove Airport. A section of the hanger roof was blown off by the winds there. Wind gusts of 70 MPH were received from both Algona and Wesley in Kossuth County. In Worth County, 70 MPH winds blew a three foot diameter tree onto a squad car in Northwood. Farther to the west, winds of 69 MPH were reported at Denison in Crawford County. Wind gusts in the 60 to 70 MPH range were too numerous to mention. Damage was widespread over the northwest half of the state ranging from fallen trees to shingle damage and blown over outbuildings. Over the southeast half of the state damage was not as widespread with most being in the form of broken branches, shingle damage, and a few fallen trees. Two people were injured in Thompson in Winnebago County. High winds toppled a camper in a recreational park in town. The camper toppled end over end with the two occupants treated and released in local hospital. Two others were injured in Hancock County as winds blew a car off of the road near Crystal Lake.

A late winter storm took aim on Iowa on the 15th. Initially, a large amount of very warm air was drawn north into the state, sending temperatures into the 50s over the southern third of the state. This caused a considerable amount of snow melt during the day on the 14th. During the early morning of the 15th, rain began to breakout over the southeast part of the state. During this time, a complex weather system was taking shape over the southwest High Plains. Two upper level systems merged over the central U.S., forming one low pressure system over south central Kansas by the morning of the 15th. During this time, cold air began to sink south into Iowa. the low tracked east across Missouri, eventually passing just south of St. Louis. A large precipitation shield formed on the north and west sides of the low. This deformation zone precipitation remained stationary for several hours. Rain changed to snow over central Iowa by the early afternoon hours of the 15th, with snow falling over most of the south half of the state by the mid evening hours. Snow fell heavily through the night with a large area of eight inches or more reported from parts of central Iowa, south into south central Iowa. The heaviest snow fall over the south central counties. A National Weather Service off-duty employee measured 14 inches of snow in central Decatur County. In nearby Lamoni, a NWS observer reported 12.4 inches from the storm. A band of very heavy snow, about 25 miles wide, extended from Lamoni northeast into Marion County. Ten inch plus reports were received in this area, with a narrow area of 12 inch plus amounts extending from Lamoni into Clarke and southeast Marion Counties. There was a sharp cut off of the heavy snowfall as you went northwest. Des Moines was near the northwest edge of the snow. Nearby Ames to the north received about an inch, while the NWS office in Johnston on the north side of the metropolitan area picked up 5.1 inches. Just 10 miles to the south of the NWS office, 8.2 inches was measured in the city of Windsor Heights. Even though the winds during the event were in the 20 to 40 MPH range, there was little blowing snow due to the very wet nature of the snow. Some drifting occurred and caused some problems with travel conditions. The very wet nature of the snow also caused some power outages. Snow caked on trees and power lines. A few branches were broken by the weight of the snow, resulting in the power outages. Nearly all schools across the southeast third of the state were closed by the storm.

A very intense storm system moved into the wester U.S. during the first and middle part of the week. This system began to affect the central U.S. by the middle of the week as pieces of energy lifted northeast from the main system. The weather made a turn for the worse on the evening of the 7th and early morning of the 8th as the first round of freezing precipitation began. This event was not a major event, but did cause glazing over a good part of the state and resulted in many school closings. Very warm and humid air streamed north ahead of the main system during the day on the 8th. Surface dew point temperatures rose into the 60s across southeast Kansas into central Missouri. In contrast to that, Arctic high pressure was poised to the north of Iowa. A sharp frontal boundary extended from Kansas into southeast Iowa. While the southeast corner of the state saw temperatures soar into the low 60s, northwest Iowa fell into the single digits. Warm air aloft, with a layer of air as warm as 55 degrees F., was in place over Iowa. Rain began to fall during the afternoon of the 8th and continued through the night. Thunderstorms accompanied the rain, increasing amounts of ice accumulation considerably. Nearly all of the southeast two thirds of the state picked up one quarter to one half inch of ice accumulation. There were numerous reports of fallen tree limbs and power outages. Damage occurred due to falling limbs as well as freezing damage caused by power outages. Fortunately, widespread power outages did not occur. Road surfaces became completely ice covered over all of the state. There were hundreds of reports of people falling on the ice, resulting in injury. Nearly all activities in the state were called off for the 9th. Travel became very hazardous. Reports of accidents and jack-knifed trucks were far too numerous to mention. In large part this was because of the icing, but also due to a winter storm which will be mentioned below.

The first major winter storm system in nearly two years struck Iowa during the night of the 10th through the day on the 11th. A large Arctic high pressure area was poised to the northwest of Iowa. Cold air spilled south into Iowa with temperatures falling into the single digits above and below zero over nearly all of the state prior to the storms beginning. During the afternoon of the 10th, low pressure began developing over the southern Rockies. The surface low took a track northeast passing near Saint Louis, MO to just north of Indianapolis, IN by late on the afternoon of the 11th. This track was similar to the track taken by the last significant snowstorm to affect much of Iowa on 31 December 1998 through 01 January 1999. Two factors took place to produce the snow in Iowa. Initially, snow broke out over the state as warm air was lifted over the cold dome during the evening of the 10th into the early morning of the 11th. This isentropic lift zone was replaced by the dynamics of the storm itself toward dawn on the 11th when heavier snow developed. Some of the snowfall was convective over the far southern part of the state. Nearly every reporting station in the Des Moines CWA reported at least 6 inches of snow from this system. Six to eight inches of snow were common over the north half of the state, while over the south half snowfall amounts were generally in the nine to twelve inch range. The heaviest snow band was generally across the second tier of counties north of the Missouri border. Some convection took place across that area which enhanced the snowfall. The heaviest snowfall total came from the Ottumwa area, where fourteen inches of snow was recorded. Several locations were close to a foot from Ottumwa west toward Osceola. Coming in close behind was Indianola, in Warren County, with eleven inches. The snow hampered travel in many areas, but now as badly as is often the case. The light fluffy nature of the snow made it fairly easy to blow off the highways. Many of the roads were reported only partially snow covered even during the height of the storm. The light nature of the storm did present some other problems however. Gusty northerly winds of 20 to 35 MPH produced significant drifting and some blowing of the snow. The biggest problem was along east to west highways. Travel was not recommended over the south third of Iowa by the late afternoon hours. Schools closed across most of the state by the afternoon of the 11th and many remained closed on the 12th as well. Numerous businesses closed and some Government offices closed early on the 11th. Another problem with this storm was with the cold temperatures and the winds. Temperatures close to zero F. combined with the 20 to 35 MPH winds produced wind chill values across the entire state in the 35 to 50 degree below zero range. Although not unusual for Iowa, these readings were colder than had been experienced during the past few winters. Actual property damage was quite minor during this event. There were report of spotty power outages caused by the cold and some icing on power lines. The winds were of such speed that some "galloping" of power lines was observed. With the very cold temperatures, the wires were brittle and susceptible to breakage. No long lasting or extended power outages were reported.

A very unstable airmass was over Iowa during the morning hours of the 5th. CAPE values were well over 4000 J/kg at sunrise with lifted indices near -10 C. Thunderstorms erupted in two clusters around 1200 UTC. The first cluster went up over north central Nebraska, the second over northwest and west central Iowa. The cluster over Iowa produced VIL levels of 80 kg/m/m over west central Iowa. Even with the VIL values so high, only pea size hail occurred with the cell. As the morning progressed, the cluster in western Iowa advanced east and a mesoscale convective vorticity center formed within the cluster. By mid to late morning, the cluster took on a small bow echo shape in its southwest quadrant. The bow echo turned southeast and caused wind damage in an area extending from Guthrie County...southeast into Monroe County. Winds of 60 to 70 MPH were common. Winds estimated around 85 MPH tore through Dallas County north of De Soto. Two airplane hangers were destroyed and several ultra light aircraft were damaged. Damage in the area was estimated at around $100,000. The same storm system struck the west side of the Des Moines metropolitan area. High winds caused considerable tree and power line damage. At one point, power was knocked out to about 25,000 homes. A major transmission line was taken down in West Des Moines as the winds toppled three power poles. One housing development lost between 50 and 60 trees as the winds blew through. Des Moines was certainly no exception. Tree and power line damage was very widespread in a broad band from west central into southeast Iowa. As the afternoon progressed, the cluster of thunderstorms that was in north central Nebraska advanced into western Iowa. The two merged as rapid development occurred along the outflow from the first cluster was overtaken by the second. Thunderstorms became severe over southwest Iowa with one inch diameter hail damaging crops in Union County. The storms were persistent with very heavy rainfall the result. Flash flooding occurred in parts of Union and Adams Counties as 3 to 5 inches of rain fell. Several roads were under water for a short time, however the water receded quickly. Southwest Iowa was not the only place to experience flooding. Considerable urban and small stream flooding took place in the Des Moines metropolitan area as well. Walnut Creek, on the west side of Des Moines, rose 7 feet in just one hour. It crested just below flood stage. Numerous city streets were covered in water, at times up to 4 feet in depth.

A very dynamic situation took shape over Iowa as an unseasonably strong upper level trough of low pressure punched southeast into the state. Deep tropical moisture was in place at the time with surface dew points in the upper 60s to mid 70s across the region. Several rounds of convection had taken place across the state during previous days, leaving several boundaries in place. One of the boundaries merged with an east-west warm frontal system over southern Iowa. Thunderstorms erupted during the morning hours. These storms brought a round of high winds and some hail to central into northeast Iowa. Hail was not that large with the storms with most reports under one inch in diameter. Gusty winds were widespread however. Winds of 60 to 75 MPH were fairly common from Des Moines, northeast into the Waterloo area. There were numerous reports of trees down. Structural damage occurred on a maintenance garage in Des Moines as 60 to 70 MPH winds blew through. High winds also took down high tension lines in the Ankeny area. Farther to the north, a semi-tractortrailer truck was blown off a highway in Marshall County. The storms continued northeast into the Waterloo area, causing power outages and downed trees in the metropolitan area. As the storms moved through Jasper County, lightning struck a driver education car in the town of Newton. Though nobody was injured, three of the cars tires were blown out and damage was done to the engine by the lightning strike.

The weather situation during the afternoon was similar to that had taken place in the morning with the exception that the convection in the afternoon was ahead of the cold front instead of the warm front. The upper air pattern remained very dynamic with a powerful upper level jet stream punching into Iowa. The airmass was very unstable. Thunderstorms erupted quite rapidly during the early afternoon hours to the west of Iowa. They moved into the state during the early afternoon with several reports of tornadoes in the far west. The storms weakened somewhat before entering the Des Moines CWA. They took on the form of a line echo wave pattern as they headed across the state. Portions of the line bowed out and produced high winds in many areas. Indeed, high winds was the main severe threat with this line as it raced across the state. There were numerous reports of trees and power lines downed by the high winds. Gusts to around 80 MPH swept into Cass County as the line moved through. Fortunately, this gust occurred in largely open area. The storms caused more structural damage as they headed into the more populated central Iowa counties. High winds damaged a farmstead in Story County south of Collins. Another farmstead north of Collins sustained damage to a barn and part of the house. As the storms progressed east, high winds flattened a barn and broke windows out of a house southwest of State Center in Marshall County. A tornado dropped out of the storm as it moved across Marshall County as well. The track was intermittent, but the tornado did cause damage to at least two farmsteads along its path. Another storm produced a brief tornado touchdown in Tama County. The tornado did little damage, but did manage to hit and knock over a couple of transformers east of Garwin. There was little hail reported with the storms, however one inch diameter hail was reported in Grundy County as Dike. As the thunderstorms moved through the Calhoun County area, lightning struck a gas meter on a house in Farnhamville. The lightning blew out the gas meter, melted the phones in the home, and caused some structural damage to the building itself.