A weak cold front dropped south across the state during the afternoon of the 7th. High temperatures reached the mid to upper 90s, with surface dewpoint values in the upper 50s to mid 60s.
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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.
A weak cold front dropped south across the state during the afternoon of the 7th. High temperatures reached the mid to upper 90s, with surface dewpoint values in the upper 50s to mid 60s. CAPE increased to around 2000 J/kg, however the atmosphere was very weakly sheared with under 20 kts of effective shear available. There was considerable downdraft CAPE available with around 1800 J/kg present. A small area of thunderstorms developed during the heat of the afternoon. Many of them produced brief heavy rain and gusty winds. One storm in Madison County produced an apparent microburst. It tore the siding from a house east of Macksburg and also blew windows out of the house.
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 7, 11:46 AM CST, 2 hours 29 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 1246 PM CDT TUE AUG 7 2012 .SHORT TERM /TODAY/... UPDATED ZONES FOR HIGHER TMAX ACROSS THE SOUTH WITH STILL SOME POTENTIAL FOR CONVECTION THERE. NORTH ON TRACK. OTHERWISE NO CHANGES. .PREVIOUS SHORT TERM /TODAY/... MAIN FORECAST CONCERN IS WITH MAX TEMPS AND POPS WITH A WEAK COLD FRONT DRIFTING SOUTH ACROSS THE STATE TODAY. NAM IS THE WARMEST MODEL WITH PUTTING SEVERAL AREAS WELL INTO THE UPPER 90S ACROSS THE SOUTH. WENT COOLER THAN THE NAM AND WARMER THAN THE GFS/ECMWF/SREF FOR MAX TEMPS TODAY...ESPECIALLY OVER THE SOUTH WHERE THE FRONT LOOKS TO TAKE ITS TIME DRIFTING SOUTH. MODELS ARE IN DECENT AGREEMENT WRT THE TIMING OF FRONT MOVING INTO SOUTHERN IOWA BY LATE THIS MORNING INTO THE EARLY AFTERNOON. NOT MUCH MOISTURE OR FORCING WITH THIS FRONT AND HAVE LOW CONFIDENCE WITH ANY WIDESPREAD PRECIP. LATEST NSSL/SPC 4.0KM WRF MODEL RUNS DEPICTING A FEW SPOTTY STORMS TO DEVELOP PAST 18Z ACROSS THE SOUTHWEST. .LONG TERM /TONIGHT THROUGH MONDAY/... FRONTAL BOUNDARY WILL SETTLE SOUTH INTO NORTHERN MISSOURI TONIGHT BEFORE WASHING OUT. UPPER LEVEL SHORT WAVE ENERGY OVER MONTANA AND ARCHING INTO SRN BRITISH COLUMBIA THIS MORNING...WILL DROP SOUTHEAST TODAY AND ARRIVE LATE TONIGHT. MID LEVEL CLOUDINESS WILL BE ON THE INCREASE IN ADVANCE OF THE SYSTEM. SHOWERS AND THUNDERSTORMS WILL BE ON THE INCREASE AS WELL PRIMARILY AFTER MIDNIGHT OVER THE CENTRAL AND WEST. ENHANCED UVV WILL BEGIN TO REACH THE EAST TOWARD 12Z. A WEAK SFC LOW PRESSURE REFLECTION WILL PASS THROUGH THE STATE INTO THE AFTERNOON AND THIS WILL KEEP THE THREAT FOR CONVECTION GOING. HIGH TEMPERATURES WEDNESDAY WILL BE LIMITED BY CLOUD COVER MUCH OF THE DAY. SOME AREAS MAY REBOUND IN THE AFTERNOON AS SKY CONDITIONS BEGIN TO SCATTER FROM THE WEST. A SECOND MORE SIGNIFICANT UPPER LEVEL SYSTEM WILL DIVE SOUTHEAST THROUGH THE NORTHERN PLAINS AND GREAT LAKES REGION ON THURSDAY WITH THE ASSOCIATED UPPER LEVEL PV ANOMALY CLIPPING INTO NORTHEAST IOWA. A FEW SHOWERS AND ISOLATED THUNDERSTORMS WILL BE ASSOCIATED WITH THIS SYSTEM MAINLY ALONG ALONG THE MISSISSIPPI VALLEY AND TO THE EAST. SOME OF THIS ACTIVITY MAY AFFECT THE EASTERN FRINGES OF THE FORECAST AREA AS WELL. THE OTHER ASPECT OF THIS SYSTEM IS THE INFLUX OF MUCH COOLER CANADIAN AIR ARRIVING INTO THE STATE. EXPECT OVERNIGHT LOW TEMPERATURES BY FRIDAY MORNING TO DROP INTO THE 50S FOR MUCH OF THE AREA AND HIGHS ONLY IN THE 70S FOR FRIDAY. CANADIAN HIGH PRESSURE WILL SETTLE OVER THE REGION FOR FRIDAY NIGHT AND CERTAINLY POSSIBLE SOME AREAS DROP INTO THE 40S BY SATURDAY MORNING. ANOTHER POTENT SHORT WAVE IS EXPECTED TO ARRIVE SATURDAY AFTERNOON AND EVENING AND WILL BRING ANOTHER CHANCE FOR PRECIPITATION. VERY LIKELY THIS ACTIVITY WILL BE FIGHTING LOW LEVEL DRY AIR FROM THE SLOW MOVING HIGH PRESSURE TO THE EAST WHICH WOULD LIMIT PRECIPITATION AMOUNTS. THE END OF THE PERIOD IS EXPECTED TO BE SEASONAL AND DRY SUNDAY AND MONDAY. && .AVIATION...07/18Z POST FRONTAL CONVERGENCE TAKING PLACE OVER NORTH CENTRAL IOWA AT THIS TIME...BUT SO FAR CONVECTION HAS NOT TAKEN PLACE. BEST CHANCES APPEAR OVER FAR SOUTH...SOUTH OF ALL SITES...BUT WILL NEED TO MONITOR THIS AFTERNOON IF CONVERGENCE INCREASES ALONG US HIGHWAY 30 AND AREAS SOUTH WHICH WOULD MEAN UPDATES NEEDED FOR KDSM AND KOTM. OTHERWISE VFR CIGS AND GENERALLY LIGHT WINDS UNDER 12KTS ARE EXPECTED THROUGH END OF TAF PERIOD. WILL ALSO EVALUATE OVERNIGHT PERIOD FOR THUNDER CHANCES AND MAKE CHANGES IF NECESSARY PRIOR TO 00Z PACKAGE./REV && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...PODRAZIK/REV AVIATION...REV LONG TERM...DONAVON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 429 AM CDT TUE AUG 7 2012 IAZ027-028-033>039-044>050-057>062-070>075-081>086-092>097-080930- 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- 429 AM CDT TUE AUG 7 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND SOUTH CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT ISOLATED NON SEVERE THUNDERSTORMS ARE POSSIBLE TODAY. SCATTERED THUNDERSTORMS ARE EXPECTED TONIGHT...MAINLY AFTER MIDNIGHT. A SEVERE STORM WITH 60 MPH WINDS AND QUARTER SIZED HAIL IS POSSIBLE TONIGHT. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY SCATTERED THUNDERSTORMS ARE POSSIBLE WEDNESDAY. CHANCES FOR STORMS WILL CONTINUE EAST OF INTERSTATE 35 WEDNESDAY NIGHT AND THURSDAY. ADDITIONAL CHANCES FOR THUNDERSTORMS ARE FORECAST FOR LATE SATURDAY AND SATURDAY NIGHT. THE THREAT FOR SEVERE WEATHER IS LOW DURING THE PERIOD. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. IAZ004>007-015>017-023>026-080930- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN- 429 AM CDT TUE AUG 7 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE POSSIBLE TONIGHT...MAINLY AFTER MIDNIGHT. A SEVERE STORM MAY OCCUR WITH 60 MPH WINDS AND QUARTER SIZED HAIL. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY SCATTERED THUNDERSTORMS ARE POSSIBLE WEDNESDAY. CHANCES FOR STORMS WILL CONTINUE EAST OF INTERSTATE 35 WEDNESDAY NIGHT AND THURSDAY. ADDITIONAL CHANCES FOR THUNDERSTORMS ARE FORECAST FOR LATE SATURDAY AND SATURDAY NIGHT. THE THREAT FOR SEVERE WEATHER IS LOW DURING THE PERIOD. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 300 PM CDT TUE AUG 7 2012 IAZ092-093-072100- RINGGOLD-TAYLOR- 300 PM CDT TUE AUG 7 2012 ...GUSTY WINDS WITH THE THUNDERSTORMS THIS AFTERNOON... AT 256 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER EXTREME WEST CENTRAL RINGGOLD COUNTY... MOVING SOUTHEAST AT 25 MPH. WINDS UP TO 50 MPH...BRIEF HEAVY DOWNPOURS...ARE POSSIBLE WITH THIS STORM. LOCATIONS IMPACTED INCLUDE... DIAGONAL... BENTON... DELPHOS... MOUNT AYR... KELLERTON... GUSTY WINDS MAY CAUSE SMALL BRANCHES TO BE BLOWN DOWN...AND LOOSE OBJECTS TO BLOW AROUND. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. COGIL
The Des Moines radar (KDMX), 67 km away, was scanning. The volume nearest the first event began at 20:15 UTC.
1 thunderstorm wind. Local standard time, as filed.
A resident reported the siding was torn off of a house and outbuilding. Windows were also blown out of the house and power was out.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2012Every state in 2012This day in weather historyWarnings in Iowa, August 2012
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: 389127.