Strong thunderstorms formed over central Iowa during the morning hours of the 4th. The ground was already quite saturated, resulting in rapid runoff of the heavy rainfall.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DMX wrote it up.
Strong thunderstorms formed over central Iowa during the morning hours of the 4th. The ground was already quite saturated, resulting in rapid runoff of the heavy rainfall. Rainfall for the most part ranged from 1 to 3 inches in a short period of time. This resulted in flash flooding in parts of central Iowa. As the water ran off, rises in mainstem river systems took place in central toward southeast Iowa. The river flooding itself was relatively minor and short lived.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Des Moines, IA wrote its last area forecast discussion before the first event at Aug 3, 11:42 PM CST, 1 hour 34 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 1242 AM CDT TUE AUG 4 2010 ...UPDATED FOR 06Z AVIATION DISCUSSION... .SHORT TERM /TONIGHT/... QUASI-STATIONARY FRONTAL BOUNDARY IS SET UP OVER SOUTHERN IOWA/NORTHERN MISSOURI...BUT CONVERGENCE SEEMS LACKING ALONG THE BOUNDARY. NAM/GFS CONSISTENT IN BRINGING PRECIP ALONG SOUTHERN IOWA WHERE ECMWF/SREF BOTH EXPAND PRECIP AREA INTO NORTHERN IOWA. FEEL THE NAM/GFS TO BE MORE REPRESENTATIVE. MOISTURE TRANSPORT SHOULD BE FAIRLY WEAK TONIGHT AS WEST-SOUTHWESTERLY LLJ REMAINS UNDER 20 KTS AS INDICATED BY MODELS...HOWEVER AIRMASS IS ALREADY FAIRLY MOIST WITH PWATS OF AROUND 2.4 INCHES. FORWARD AND BACKWARD PROPAGATING CORFIDI VECTORS BOTH INDICATING STORM MOTION SHOULD BE PROGRESSIVE TONIGHT. HIGH PWATS NOTWITHSTANDING...BELIEVE THE LACK OF ANY STRONG FORCING AND PROGRESSIVE STORM MOTION WILL PRODUCE LOWER QPF THAN GUIDANCE. .LONG TERM /WEDNESDAY THROUGH TUESDAY/... HUDSON BAY UPPER TROUGH SHOULD BE STRONG ENOUGH TO PUSH PERSISTENT QUASI-STATIONARY BOUNDARY WELL SOUTH BY WEDNESDAY NIGHT. LINGERING THUNDERSTORMS FROM TONIGHT PLUS SOME SHORTWAVE ENERGY MOVING INTO CENTRAL IA IS ENOUGH TO JUSTIFY SMALL POPS ON WEDNESDAY. SUBSIDENCE BEHIND THE WAVE WEDNESDAY NIGHT COUPLED WITH 850 MB DRYING AND WEAK COLD ADVECTION SUGGEST DRY CONDITIONS SO PCPN WAS REMOVED FROM THE FORECAST. RELIEF FROM HIGH HUMIDITY THURSDAY AND THURSDAY NIGHT AS SURFACE RIDGE BUILDS IN. BASED TEMPS ON BLEND OF MET/MAV WHICH APPEARED REASONABLE IN LOWERING TEMPS TO NEAR NORMAL. IN THE DAY 4-7 RANGE /FRIDAY THROUGH TUESDAY/...BASED FORECAST ON A COMBINATION OF 00Z GFS ENSEMBLES...00Z ECMWF AND TO A LESSER EXTENT THE 06Z GFS. HUDSON BAY UPPER TROUGH FORECAST TO FLATTEN THE UPPER RIDGE EARLY IN THE PERIOD OVER THE GREAT LAKES AND OHIO VALLEY. IN TURN...THE RIDGE IS FORECAST TO BUILD NORTH OVER THE PLAINS BY THE END OF THE WEEK AND INTO THE WEEKEND AND BEYOND. THE MODELS ARE IN FAIR AGREEMENT WITH THE OVERALL PATTERN. SURFACE HIGH PRESSURE RIDGE SHOULD BE NEAR IOWA ON FRIDAY BEFORE IT MOVES EAST ALLOWING RETURN FLOW DO DEVELOP UNDER RISING 500 MB HEIGHTS. KEPT WAA THUNDERSTORM CHANCES GOING AS DEEPER MOISTURE AND WARM AIR RETURN. BY DAYS 6-7...RIDGE SHOULD BE WELL ESTABLISHED PUSHING THE WESTERLIES NORTH OF IA. THIS SHOULD DECREASE PRECIPITATION CHANCES. CENTRAL IA SHOULD BE WELL INTO THE WARM AIR AND EXPECT TO SEE HOT AND HUMID CONDITIONS. MADE SOME ADJUSTMENTS COMPARED TO HPC GUIDANCE INCLUDING SLIGHTLY WARMER TEMPERATURES AND HIGHER DEWPOINT TEMPERATURES. .AVIATION...04/06Z MCS PUSHING EASTWARD ACROSS SOUTHERN IOWA WILL BRING IFR CEILINGS TO KDSM...AND KOTM BEFORE CLEARING THE AREA. WILL ALSO SEE GUSTY WINDS AT THESE SITES ALONG WITH THUNDER. HAVE INCLUDED LOWER CEILINGS AT MORE NORTHERN TAF SITES AS EXPECT OCCASIONAL SHOWERS TO MOVE THROUGH THE NORTH. ALSO...ANTICIPATING EARLY MORNING FOG DEVELOPMENT AT ALL SITES. WEAK HIGH PRESSURE WILL BUILD IN TOMORROW...AND LINGERING FOG WILL BURN OFF BY MID MORNING...LEAVING VFR CEILINGS THROUGH THE REMAINDER OF THE PERIOD. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...HINSBERGER AVIATION...WILKINS LONG TERM...JAJ
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 825 PM CDT TUE AUG 3 2010 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086- 092>097-041100- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN- WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE- BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER- POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION- CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE- DAVIS- 825 PM CDT TUE AUG 3 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF CENTRAL IOWA. .DAY ONE...TONIGHT ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED OVERNIGHT ACROSS CENTRAL IOWA...WITH THE MAIN THREAT SOUTH OF HIGHWAY 20. SEVERE WEATHER IS NOT EXPECTED AT THIS TIME. HOWEVER...HEAVY RAINFALL MAY OCCUR WITH LOCALIZED FLOODING POSSIBLE. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY SCATTERED THUNDERSTORMS ARE EXPECTED INTO WEDNESDAY MORNING BEFORE GRADUALLY ENDING BY AFTERNOON. AT THIS POINT...SEVERE WEATHER IS NOT EXPECTED. ADDITIONAL THUNDERSTORMS CHANCES ARE EXPECTED BY THIS WEEKEND...HOWEVER IT IS TOO EARLY TO DETERMINE SEVERE WEATHER CHANCES. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME. CC
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1130 PM CDT TUE AUG 03 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1112 PM TSTM WND GST WSW FONTANELLE 41.29N 94.57W
08/03/2010 M62 MPH ADAIR IA MESONET
SCHOOLNET INSTRUMENT MEASURED A WIND GUST TO 54 KT / 62
MPH.
&&
LEEPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1243 AM CDT WED AUG 04 2010
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1140 PM TSTM WND DMG S EARLHAM 41.49N 94.12W
08/03/2010 MADISON IA TRAINED SPOTTER
TRAINED SPOTTER REPORTED 1 FOOT DIAMETER LIMBS DOWN ON
THE SOUTH SIDE OF EARLHAM.
&&
CCOGILThe national radar mosaic for the moment the first event began.
5 flood. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2010Every state in 2010This day in weather historyWarnings in Iowa, August 2010
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 248931, 248932, 248942, 248940, 248929.