A cold front moved into Iowa during the afternoon. Though much of the convection was well to the east, a narrow band of thunderstorms formed along the cold front.
Every event with a place to put it. Tap one for its entry below.
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 cold front moved into Iowa during the afternoon. Though much of the convection was well to the east, a narrow band of thunderstorms formed along the cold front. The SPC mesoanalysis had very little CAPE, but this was right on the cold front in the transition from the humid airmass to a cool airmass. LCLs were below 750 m, and 0-3 km CAPE was around 75 J/kg. The storm produced some strong winds near Zearing causing some damage to one farmstead. The strong winds resulting in damage to a sheet metal building and nearby crops.
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 Sep 3, 5:28 PM CST, 2 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 628 PM CDT SAT SEP 3 2011 ...UPDATED FOR THE 00Z AVIATION DISCUSSION... .SHORT TERM /TONIGHT/... ONGOING THUNDERSTORM ACTIVITY WILL CONTINUE SOUTH AND EAST OF AN ADVANCING COLD FRONT IN NORTHWEST IOWA. MODELS ARE IN GOOD AGREEMENT WITH TIMING OF FRONT CLEARING THE FORECAST AREA B/T 00-03Z SUNDAY. INSTABILITY HAS BEEN TARNISHED BY THIS MORNINGS THUNDERSHOWER ACTIVITY AND HAVE LOW CONFIDENCE WITH ANY SEVERE POTENTIAL THE REST OF THIS AFTERNOON AND INTO THE EVENING HOURS. MAY SEE SOME RE-DEVELOPMENT WITH THE FROPA ACROSS THE CENTRAL AND SOUTHEAST FORECAST AREA...BUT WITH LESS THAN 500 J/KG OF MLCAPE NOT EXPECTING ANYTHING TOO SIGNIFICANT. DECREASED POPS PAST 03Z AND CONFINED THEM TO ONLY THE FAR SOUTHEAST PORTION OF THE CWA. .LONG TERM /SUNDAY THROUGH SATURDAY/... LITTLE WEATHER OF NOTE IN THIS PERIOD. EFFECTS FROM CURRENT SYSTEM SHOULD BE SOUTH AND EAST OF IA BY SUNDAY MORNING. PATTERN OF ROCKIES RIDGE/ERN CONUS TROUGH WILL BE IN PLACE THROUGH AT LEAST MIDWEEK WITH EXPANSIVE PLAINS SURFACE HIGH PRESSURE KEEPING FAIR AND COOL WEATHER IN PLACE. TEMPERATURES SHOULD BE NEAR GUIDANCE BASED ON RAW MODEL TEMPS. EXTRATROPICAL REMNANTS OF TS LEE WILL BE THE ONLY CONCERN FOR LATE NEXT WEEK. RECENT GFS/GEFS/GEM AND 00Z ECMWF ENSEMBLES SUGGEST THIS SYSTEM WILL REMAIN FAR ENOUGH EAST TO KEEP OUR FORECAST DRY. HOWEVER OPERATIONAL ECMWF HAS STEADILY BEEN TRENDING FARTHER WEST WITH TIME...WHICH IS ALSO NOW HINTED AT BY 12Z GFS TO A LESSER EXTENT. THIS WOULD SUGGEST AT LEAST SLIGHTS NEED TO BE INTRODUCED FOR FRI AND/OR SAT CENTRAL AND EAST AS SYSTEM BACKS TOWARD MS RIVER. BECAUSE OF THIS UNCERTAINTY...AND THE FACT THAT ITS DAYS 6 AND 7...WILL KEEP THIS PERIOD DRY FOR NOW BUT CONTINUE TO WATCH. && .AVIATION...04/00Z SHOWERS AND THUNDERSTORMS DIMINISHING ACROSS THE AREA EARLY THIS EVENING. A COLD FRONT WITH MUCH DRIER AIR OVER NORTHWEST IOWA...WILL QUICKLY SWEEP SOUTHEAST THIS EVENING AND BRING WIDESPREAD VFR CONDITIONS AND A SWITCH TO NORTHWEST WINDS. LOCAL MVFR CIGS WILL BE POSSIBLE BEFORE THE DRY AIR ARRIVES. VFR CONDITIONS AND GUSTY NW WINDS WILL PREVAIL ON SUNDAY. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...PODRAZIK AVIATION...DONAVON LONG TERM...SMALL
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 347 PM CDT SAT SEP 3 2011 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- 347 PM CDT SAT SEP 3 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR MUCH OF CENTRAL IOWA. .DAY ONE...THIS AFTERNOON AND TONIGHT SCATTERED THUNDERSTORMS ARE EXPECTED THIS EVENING. SEVERE WEATHER IS NOT ANTICIPATED. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. SMALL
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 158 PM CDT SAT SEP 3 2011 IAZ097-031930- DAVIS- 158 PM CDT SAT SEP 3 2011 ...STRONG THUNDERSTORM TO AFFECT SOUTHEAST DAVIS COUNTY... AT 156 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER SOUTH CENTRAL DAVIS COUNTY...MOVING EAST AT 35 MPH. NICKEL SIZE HAIL...WINDS GREATER THAN 40 MPH...FREQUENT CLOUD TO GROUND LIGHTNING...BRIEF MODERATE DOWNPOURS...ARE POSSIBLE WITH THIS STORM. * THE THUNDERSTORM WILL BE NEAR... PULASKI BY 205 PM CDT... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS TREES. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. PODRAZIK
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 238 PM CDT SAT SEP 3 2011 IAZ034-035-032030- CALHOUN-WEBSTER- 238 PM CDT SAT SEP 3 2011 ...A STRONG THUNDERSTORM WILL MOVE ACROSS CALHOUN AND WEBSTER COUNTIES... AT 233 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 23 MILES SOUTHWEST OF FORT DODGE...MOVING EAST AT 25 MPH. WINDS GREATER THAN 40 MPH...BRIEF MODERATE DOWNPOURS...ARE POSSIBLE WITH THIS STORM. * THE THUNDERSTORM WILL BE NEAR... RINARD BY 245 PM CDT... SOMERS AND KNIERIM BY 250 PM CDT... 8 MILES NORTH OF GOWRIE AND 8 MILES SOUTH OF BARNUM BY 305 PM CDT... CALLENDER AND MOORLAND BY 310 PM CDT... OTHO AND FORT DODGE BY 325 PM CDT... LEHIGH BY 330 PM CDT... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. BOKSA
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 257 PM CDT SAT SEP 3 2011 IAZ017-026-032030- CERRO GORDO-FRANKLIN- 257 PM CDT SAT SEP 3 2011 ...A STRONG THUNDERSTORM WILL MOVE ACROSS SOUTHERN CERRO GORDO AND NORTHERN FRANKLIN COUNTIES... AT 251 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER EXTREME SOUTH CENTRAL CERRO GORDO COUNTY... MOVING EAST AT 30 MPH. WINDS GREATER THAN 40 MPH...BRIEF MODERATE DOWNPOURS...ARE POSSIBLE WITH THIS STORM. * THE THUNDERSTORM WILL BE NEAR... ROCKWELL BY 305 PM CDT... DOUGHERTY BY 315 PM CDT... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. BOKSA
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 324 PM CDT SAT SEP 3 2011 IAZ025-035>037-032130- HAMILTON-HARDIN-WEBSTER-WRIGHT- 324 PM CDT SAT SEP 3 2011 ...A STRONG THUNDERSTORM WILL AFFECT EASTERN WEBSTER COUNTY AND NORTHERN HAMILTON COUNTY... AT 319 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER CENTRAL WEBSTER COUNTY...MOVING EAST AT 30 MPH. WINDS GREATER THAN 40 MPH...BRIEF HEAVY DOWNPOURS...ARE POSSIBLE WITH THIS STORM. * THE THUNDERSTORM WILL BE NEAR... DUNCOMBE BY 330 PM CDT... WEBSTER CITY AIRPORT BY 340 PM CDT... WEBSTER CITY AND 9 MILES SOUTH OF WOOLSTOCK BY 345 PM CDT... KAMRAR BY 350 PM CDT... BLAIRSBURG BY 400 PM CDT... WILLIAMS BY 415 PM CDT... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. BOKSA
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 424 PM CDT SAT SEP 3 2011 IAZ026>028-037>039-032330- BLACK HAWK-BREMER-BUTLER-FRANKLIN-GRUNDY-HARDIN- 424 PM CDT SAT SEP 3 2011 ...STRONG THUNDERSTORMS OVER NORTHEAST IOWA LATE THIS AFTERNOON... AT 418 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 27 MILES NORTH OF WATERLOO TO 6 MILES WEST OF IOWA FALLS...MOVING EAST AT 30 MPH. WINDS GREATER THAN 40 MPH AND MODERATE TO HEAVY RAINS ARE POSSIBLE WITH THESE STORMS. LOCATIONS IMPACTED INCLUDE... IOWA FALLS... FREDERIKA... ACKLEY... SHELL ROCK... APLINGTON... WAVERLY... TRIPOLI... SUMNER... PARKERSBURG... JANESVILLE... STOUT... NEW HARTFORD... READLYN... DENVER... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THESE STORMS HAVE PASSED. SMALL
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 513 PM CDT SAT SEP 3 2011 IAZ092-032245- TAYLOR- 513 PM CDT SAT SEP 3 2011 ...STRONG THUNDERSTORM MOVING ACROSS SOUTHERN TAYLOR COUNTY... AT 509 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER SOUTH CENTRAL TAYLOR COUNTY...MOVING SOUTHEAST AT 20 MPH. WINDS GREATER THAN 40 MPH...BRIEF MODERATE DOWNPOURS...ARE POSSIBLE WITH THIS STORM. * THE THUNDERSTORM WILL BE NEAR... ATHELSTAN BY 540 PM CDT... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. BOKSA
The Des Moines radar (KDMX), 61 km away, was scanning. The volume nearest the first event began at 23:32 UTC.
1 thunderstorm wind. Local standard time, as filed.
High winds damaged farm buildings and crops.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2011Every state in 2011This day in weather historyWarnings in Iowa, September 2011
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: 331809.