Power Outage in Fort Dodge, IA

This tornado started on the east side of the Des Moines River valley southwest of Duncombe and moved quickly northeast. The tornado snapped several power poles near the intersection of Taylor Avenue and 220th Street west of Duncombe. Another outbuilding was destroyed northwest of Duncombe near the intersection of 210th Street and the Canadian National Railway. The tornado lifted not long afterwards.

Emergency manager reported numerous trees down along with power outages.

Trained spotter reported widespread power outages, upwards of 40 foot tall trees down, and estimated at least 70 mph winds. This is a delayed report.

Trained spotter reported multiple tree limbs down along with a few transformers throughout town. Power out in many locations.

Ten high tension power poles were blown down about 5 miles west of Fort Dodge.

Large trees and power lines were blown down in town.

Thunderstorms moved northeast into Iowa overnight. While overall instability was around 500 J/KG, the 0-3km MLCAPE was over 125 J/KG across southwest Iowa accounting for around a third of the overall updraft strength. Effective helicity values were nearly 500 m2/s2. The strongly sheared environment along with decent near surface instability led to the development of two tornadoes across southwest Iowa during the night. The first tornado was an EF-1 and virtually destroyed an old farm building southeast of Anita. The second more powerful tornado occurred southeast of Adair and impacted a few different farmsteads. The final farmstead encountered received EF-2 damage producing 1 injury and 1 fatality. The tornado crossed Interstate 80 and then remained in rural cropland for the remainder of the path.

An area of thunderstorms moved through the area during the previous night. As the storms moved east an area of high winds developed on the back side of the complex. High winds of 80 to 90 MPH caused damage in Calhoun and Webster Counties. Winds were recorded at 92 MPH at a Schoolnet sight in Farnhamville. High tension power lines were blown down southwest of Fort Dodge. A heat burst took place with the temperature at Farnhamville rising from 65 to 90 in a few minutes, at the Fort Dodge rise from 66 to 81 in a few minutes.

A very strong upper level low pressure trough had carved out over the western U.S. Iowa was in the strong southwest flow on the front side of this system. A surface warm front lifted north into southwest Iowa during the evening of the 5th. The airmass became quite unstable with plenty of deep moisture advection into the areas. Precipitable water values were in the 1.5 to 1.75 inch range by midnight. The lifted index fell to the -6 to -8 C. There was a reasonable amount of CAPE available with about 2500 J/kg at the onset of the event. The LCL was around 1000 meters and the freezing level was a relatively high 13,500 feet. With the warm front in the vicinity, there was a considerable amount of helicity present with values in the 300 to 550 range. During the evening of the 5th, most of the significant convection remained to the west of the DMX CWA. After midnight, the low level jet increased to 50 to 70 kts and began to veer. This helped push the convection east during the overnight hours. Strong cells developed in southwest Iowa near the warm frontal boundary. Two tornadoes occurred with this initial set of convection. An EF2 tornado touched down in Cass County. The tornado first developed right on the southern Cass County line, from highway 71 to three quarters of a mile west. Four farmsteads were damaged along county road G66 within the mile west of highway 71, producing damage up to EF1. The tornado narrowed slightly and intensified in the next mile, downing two sets of metal electrical transmission poles. The most severe damage occurred at a farm service and grain elevator business on highway 71. This was 2 miles into Cass County or 3 miles south of the town of Lyman. EF2 damage occurred at this site with winds estimated at 120-130 mph. The average path width was 100 to 200 yards, with a maximum width of about one half mile. Empty semi trailers were flipped, two tall grain bins were flattened. A large metal clad truck service building was flattened on the south end and much of the roof was off the north end. The west part of the roof of an office building was torn off and the wall collapsed. The house at the north end of the site had windows blown out and part of the roof damaged. The tornado continued north along and just east of highway 71 for another two miles causing some damage to homes with some outbuildings unroofed or destroyed. The last apparent damage along the tornado path occurred two miles northeast of Lyman where power poles were snapped. Several areas between Cumberland and Anita were also surveyed. Damage along this path was consistent with straight line winds of 70 to 90 mph. Damage included downed trees and sheet metal torn off sheds and outbuildings. A storage building in Anita was significantly damaged. A total of 115 to 120 homes were damaged in Cass County by the storm. As the night progressed, a bow echo advanced into the state from the southwest. There were several reports of high winds and hail with this line. One of the storm in the line produced a small EF0 tornado in Union County. Some damage occurred at several farmsteads along the path. This same cell produced very large hail with hail up to baseball size reported in the Afton area. The hail was wind driven, damaging skylights, windows, and cars. Hail stones were driven through car windshields and also through windows in houses. Some damage even occurred inside of two homes as the hail stones continued inside of the house. This was the most significant hail from the storms. The hail reportedly piled up several inches deep and lasted for at least 4 hours after the storm. In the survey conducted by the Emergency Manager it was found that in Afton, 236 primary buildings and 174 out buildings and garages had moderate hail damage consisting of roof damage...primarily to the slopes facing south and west. All roof vents and eves, either aluminum or plastic, were damaged. Almost 100 percent of the buildings with south-facing windows had damage to screens, broken glass storm windows, interior single and double pane windows, and in cases of plastic framed windows even the sashes and stools were damaged. All siding was damaged on those sides no matter of the material. In the rural areas around Afton, 30 of the 38 residences received moderate damage. In Arispe, 5 miles south of Afton, hail damage occurred, but was not as severe with 40 residences reporting minor damage and 30 out buildings being damaged. All together, 346 vehicles were hail damaged and many had Windows broken completely out. Twenty three campers suffered vent and sky lite damages as well as exterior damages. Hardly any of the skylights withstood the hail, either in campers or houses. Though many of the storms produced hail, much of it was under one half inch in diameter. Another brief tornado touched town in Guthrie County south of Bayard. The tornado caused EF1 damage. A roof was blown off of a building there, and blown westward. Wind was the primary threat with the storms. There were several reports of trees downed by the high winds, barns, and outbuildings being blown over or destroyed. A semi-tractortrailer was blown off of Interstate 80 west of Adair. The event turned into a significant event both in areal coverage, as well as for its variety of weather features. Flooding became a significant problem later in the event with several reports of 3 to 5 inch rainfall received. Flash flooding occurred over parts of southwest into west central Iowa. Cass, Audubon, and Carroll Counties were the hardest hit. Areal flood warnings were issued for these counties. Widespread flooding too place, with Cass County hard hit. The Governor of Iowa, Chet Culver, declared a state disaster for several counties across southwest and south central Iowa due to the flash flooding. This included Decatur County in the Des Moines CWA. Toward dawn, high winds became a problem over parts of northwest Iowa. The winds affected a 6 county area with wind gusts in the 50 to 65 MPH range for several hours.

A weak trough moved east across Iowa during the afternoon and evening of the 29th. A few thunderstorms formed along the upper level vorticity center. The atmosphere was not all that unstable with little CAPE and a nearly neutral lifted index, however the soundings did present a good straight line pattern with an inverted "V" sounding. As the thunderstorms moved through the Fort Dodge area they produced high winds. Several trees were downed as well as power line damage reported.

A very warm and unstable airmass was in place over Iowa, as had been the case for the past several days. A cold front sank southeast into the state during the afternoon and evening hours. The freezing level was very high, ranging from 15,500 to 17,000 feet across the area. The lifted indices were in the -8 range by late afternoon. There was considerable cloud debris over the northern part of the CWA, however clearing set in across the south. Temperatures soared into the mid 90s with dew point readings in the low to mid 70s. Plenty of CAPE was available with values by late afternoon in the 3500 to 4000 J/kg range. Thunderstorms fired along the front and became severe. The storms did not remain severe for very long as in spite of the linear presentation on radar, the storms became multi-cellular. The cloud shield and outflow from the storms diminished their intensity within 90 minutes of the storms becoming severe. During the early stages of the line, a tornado dropped down into Kossuth County south of Algona. The tornado tracked across a corn field and hit a two year old shed. The shed was 60 X 90 feet and was damaged significantly. The farmhouse was damaged with siding pulled off of it, however it was not directly struck. There were numerous reports of high winds of 60 up to 75 MPH across the west central into the north central counties. Numerous trees were damaged or toppled and some crop damage was reported. One of the stronger storms produced winds high enough to topple 3 power poles north of Aspinwall in Crawford County. Hail from the storms was quite limited, though spotty reports of up to dime size hail were received. One storm did produce quarter size hail in Crawford southeast of Vail during the initial stages of the storm development.

A strong push of warm and unstable air came into Iowa during the afternoon of the 16th ahead of an approaching warm front. The situation was very dynamic for mid August as a strong 70 to 100 kt jet max approached the state. Surface dew points south of the warm front were in the mid 70s. Thunderstorms erupted over northwest Iowa. Initially the storms produced hail as they were quite elevated in nature. Generally speaking, the hail was an inch or less in diameter. By late afternoon as the next round of development occurred the storms produced high winds. Wind gusts were between 60 and 80 MPH with the stronger storms. Most of the damage was limited to tree, power line, and crop damage. The winds did damage a grain bin and twisted small buildings in Humboldt southwest of the town of Humboldt.

A very humid airmass was in place over Iowa during the afternoon of the 10th into the evening. High temperatures were not all that high with upper 70s and 80s common. Dew point temperatures were in the low to mid 70s. A cold front approached Iowa from the northwest. Thunderstorms fired up along the front. The main focus of thunderstorm development was over eastern Nebraska into western Iowa. A strong low level jet developed during the early evening hours. The combination of high amounts of low level moisture and the strong low level jet impinging on the approaching front was enough to break the cap in spite of a +13 C. temperature at 700 mb over Omaha. The storms formed into a Mesoscale Convective System. Though there was some hail with the thunderstorms, the main severe weather event was high winds. The lead edge of the system transitioned into a bow echo and produced winds of 60 to 70 MPH in several locations. One of the higher winds was at the apex of the bow echo. Seventy one MPH winds swept through the Fort Dodge area of Webster County. There were numerous reports of tree damage across western into parts of central Iowa. Scattered reports were received of power poles being blown down by the high wind. Southwest of Clarion in Wright County, high winds downed several power poles for example.

Once again, very warm and humid air spread over Iowa with temperatures in the 80s to mid 90s during the afternoon of the 13th. The airmass was again very capped with 700 mb temperatures of 12 degrees C. or higher over most of the area. As a result, thunderstorms had a hard time developing. Once the thunderstorms did develop they became severe quite quickly. There was one tornado reported during the early part of the thunderstorm development. A brief touchdown occurred southeast of Ayrshire in Palo Alto County. No significant damage was reported with this tornado. The main severe weather feature with these storms was hail, though there were several reports of high winds as well. The big story was hail of an inch or more in diameter, with frequent reports of hail up to golf ball in size. Considerable crop damage was reported with soybeans being hard hit. Some reports indicate up to 50% of the soybean pots cracked open by the hail. Golf ball size hail war reported ankle deep east of Ellsworth in Hamilton County. Hail fell for a 30 minute period in Wright County at Eagle Grove. High winds also caused tree, power line, and crop damage. Trees were toppled in several locations by winds of 60 to 70 MPH. The winds also caused considerable lodging of the corn crop due in part to stalk rot brought about by the very dry weather. The down of Duncombe in Webster County was hard hit with considerable roof damage reported there.