Storm Events Database

Event Details

Event Flash Flood
-- Flood Cause Heavy Rain
State IOWA
County/Area SAC
WFO DMX
Report Source Law Enforcement
NCDC Data Source CSV
Begin Date 2007-05-06 04:35:00.0 CST-6
Begin Location 0N SAC CITY
Begin Lat/Lon 42.42/-95
End Date 2007-05-06 08:30:00.0 CST-6
Deaths Direct/Indirect 0/0 (fatality details below, when available...)
Injuries Direct/Indirect 0/0
Property Damage 50.00K
Crop Damage 0.00K
Episode Narrative 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.
Event Narrative


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All events for this episode:

Location County/Zone St. Date Time T.Z. Type Mag Dth Inj PrD CrD
Totals: 0 0 5.393M 0.00K
GRISWOLD CASS CO. IA 05/06/2007 01:40 CST-6 Tornado EF2 0 0 1.000M 0.00K
FLETCHER CHAPEL CASS CO. IA 05/06/2007 01:54 CST-6 Hail 0.75 in. 0 0 0.00K 0.00K
ANITA CASS CO. IA 05/06/2007 02:00 CST-6 Thunderstorm Wind 70 kts. EG 0 0 100.00K 0.00K
GRAVITY TAYLOR CO. IA 05/06/2007 02:20 CST-6 Thunderstorm Wind 65 kts. EG 0 0 100.00K 0.00K
ADAIR ADAIR CO. IA 05/06/2007 02:30 CST-6 Thunderstorm Wind 57 kts. EG 0 0 30.00K 0.00K
ATLANTIC CASS CO. IA 05/06/2007 02:42 CST-6 Flash Flood 0 0 50.00K 0.00K
BAYARD GUTHRIE CO. IA 05/06/2007 02:45 CST-6 Thunderstorm Wind 70 kts. EG 0 0 50.00K 0.00K
CUMBERLAND CASS CO. IA 05/06/2007 02:48 CST-6 Flash Flood 0 0 100.00K 0.00K
CORNING ADAMS CO. IA 05/06/2007 02:50 CST-6 Thunderstorm Wind 50 kts. EG 0 0 3.00K 0.00K
ATLANTIC CASS CO. IA 05/06/2007 02:55 CST-6 Flash Flood 0 0 200.00K 0.00K
CUMBERLAND CASS CO. IA 05/06/2007 02:55 CST-6 Flash Flood 0 0 200.00K 0.00K
ATLANTIC CASS CO. IA 05/06/2007 03:08 CST-6 Flash Flood 0 0 50.00K 0.00K
ADAIR ADAIR CO. IA 05/06/2007 03:12 CST-6 Thunderstorm Wind 56 kts. EG 0 0 10.00K 0.00K
BRIDGEWATER ADAIR CO. IA 05/06/2007 03:17 CST-6 Thunderstorm Wind 61 kts. EG 0 0 75.00K 0.00K
AFTON UNION CO. IA 05/06/2007 03:20 CST-6 Hail 1.75 in. 0 0 100.00K 0.00K
ARISPE UNION CO. IA 05/06/2007 03:25 CST-6 Hail 2.00 in. 0 0 100.00K 0.00K
NORTH BRANCH GUTHRIE CO. IA 05/06/2007 03:25 CST-6 Thunderstorm Wind 56 kts. EG 0 0 10.00K 0.00K
AFTON UNION CO. IA 05/06/2007 03:30 CST-6 Hail 2.75 in. 0 0 750.00K 0.00K
BAYARD GUTHRIE CO. IA 05/06/2007 03:37 CST-6 Tornado EF1 0 0 50.00K 0.00K
YALE GUTHRIE CO. IA 05/06/2007 03:37 CST-6 Thunderstorm Wind 70 kts. EG 0 0 75.00K 0.00K
THAYER UNION CO. IA 05/06/2007 03:45 CST-6 Tornado EF0 0 0 75.00K 0.00K
JAMAICA GUTHRIE CO. IA 05/06/2007 03:50 CST-6 Thunderstorm Wind 52 kts. EG 0 0 0.00K 0.00K
JAMAICA GUTHRIE CO. IA 05/06/2007 03:53 CST-6 Thunderstorm Wind 57 kts. EG 0 0 50.00K 0.00K
GRISWOLD CASS CO. IA 05/06/2007 04:15 CST-6 Flash Flood 0 0 200.00K 0.00K
NEW VIRGINIA WARREN CO. IA 05/06/2007 04:15 CST-6 Thunderstorm Wind 61 kts. EG 0 0 40.00K 0.00K
NEW VIRGINIA WARREN CO. IA 05/06/2007 04:19 CST-6 Thunderstorm Wind 61 kts. EG 0 0 50.00K 0.00K
AUDUBON AUDUBON CO. IA 05/06/2007 04:20 CST-6 Flash Flood 0 0 50.00K 0.00K
HUMBOLDT (ZONE) HUMBOLDT (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 35 kts. ES 0 0 25.00K 0.00K
KOSSUTH (ZONE) KOSSUTH (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 35 kts. ES 0 0 25.00K 0.00K
WRIGHT (ZONE) WRIGHT (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 50 kts. MG 0 0 25.00K 0.00K
WEBSTER (ZONE) WEBSTER (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 35 kts. MS 0 0 25.00K 0.00K
POCAHONTAS (ZONE) POCAHONTAS (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 35 kts. ES 0 0 25.00K 0.00K
PALO ALTO (ZONE) PALO ALTO (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 35 kts. ES 0 0 25.00K 0.00K
EMMET (ZONE) EMMET (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 56 kts. MG 0 0 25.00K 0.00K
HAMILTON (ZONE) HAMILTON (ZONE) IA 05/06/2007 04:30 CST-6 High Wind 52 kts. MG 0 0 25.00K 0.00K
SAC CITY SAC CO. IA 05/06/2007 04:35 CST-6 Flash Flood 0 0 50.00K 0.00K
AUDUBON ARPT AUDUBON CO. IA 05/06/2007 05:20 CST-6 Flash Flood 0 0 75.00K 0.00K
EXIRA AUDUBON CO. IA 05/06/2007 05:42 CST-6 Flash Flood 0 0 50.00K 0.00K
LANESBORO CARROLL CO. IA 05/06/2007 08:45 CST-6 Flood 0 0 250.00K 0.00K
GRAY AUDUBON CO. IA 05/06/2007 08:54 CST-6 Flood 0 0 250.00K 0.00K
ANITA CASS CO. IA 05/06/2007 09:18 CST-6 Flood 0 0 1.000M 0.00K
Totals: 0 0 5.393M 0.00K