The area of thunderstorms that moved into Iowa during the night decayed rapidly around sunrise. This produced high winds in a small area of central Iowa.
Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
The area of thunderstorms that moved into Iowa during the night decayed rapidly around sunrise. This produced high winds in a small area of central Iowa. A heat burst was reported by a trained observer in Marion County with 60 MPH winds. Winds of 76 MPH were measured in Mahaska County at Pella, along with a heat burst.
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 May 3, 5:56 AM CST, 49 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 656AM CDT THU MAY 3 2012 ...UPDATED AVIATION DISCUSSION... .SHORT TERM /TODAY/... FORECAST CONCERN INVOLVES THE ONGOING CONVECTION ASSOCIATED WITH A DYING MCS MOVING ACROSS THE SOUTHERN TWO-THIRDS OF THE FORECAST AREA THIS MORNING. LATEST HRRR (05Z RUN) HAS CONVECTION DISSIPATING AND MOVING EAST THROUGH 15Z AND THE 00Z 4KM WRF HAS CONVECTION DISSIPATING BY AROUND 18Z IN EASTERN PORTIONS OF THE FORECAST AREA. Q2 CURRENTLY DEPICTING RAINFALL RATES AROUND 2 IN/HR OR LESS WITHIN THE STRONGER CORES...BUT LINE IS MOVING FAIRLY PROGRESSIVE AT 30-35KTS. SO NOT ANTICIPATING MUCH FLOODING ISSUES...ESPECIALLY FURTHER EAST WITHIN THE FLASH FLOOD WATCH AREA IN NORTHEAST IOWA. CONVECTION SHOULD BE MUCH WEAKER BY THE TIME IT REACHES IT AND THUS...WENT AHEAD AND CANCELLED FLASH FLOOD WATCH. OTHER CONCERN IS WITH POTENTIAL FOR AFTERNOON CONVECTION ALONG AND SOUTH OF THE BOUNDARY IN NORTHERN IOWA. RUC/NAM/GFS ALL KEEP THE SURFACE FRONT LAID UP ALONG THE MN/IA BORDER KEEPING THE FORECAST AREA WITHIN THE WARM SECTOR. BEST INSTABILITY WILL BE LOCATED SOUTH OF HIGHWAY 30 WHERE LOW LEVEL CAPE INCREASES TO AROUND 2000-3000 J/KG BUT LOW LEVEL SHEAR VALUES NOT IMPRESSIVE. CLOUDS LEFTOVER FROM DYING MCS SHOULD LIMIT SOME OF THE DAYTIME HEATING...BUT THINKING THE WAA WILL BE STRONG ENOUGH TO BUMPED TEMPS BACK INTO THE LOWER 80S BY THIS AFTERNOON. TIMING OF AFTERNOON CONVECTION LOOKS TO BE AFTER 21Z WITH MID-LEVEL SHORTWAVE MOVING INTO WESTERN IOWA BY 00Z FRIDAY. SURFACE DEW POINTS REMAIN WELL INTO THE 60S...SO PLENTY OF MOISTURE AVAILABLE. .LONG TERM /TONIGHT THROUGH WEDNESDAY/... CURRENT LONG WAVE PATTERN...WRN CONUS TROUGH/ERN RIDGE...WILL REMAIN INTACT THROUGH MUCH OF THE PERIOD BUT WITH SLOW PROGRESS. THIS SHOULD HAVE TROUGH ONLY REACH CENTRAL CONUS BY EARLY NEXT WEEK. EXPECT CONVERGENCE FROM CURRENT NE TO MN FRONTAL BOUNDARY AND/OR OUTFLOW FROM WEAKENING WRN IA MCS TO EVENTUALLY POSITION ITSELF INTO CENTRAL/SRN IA BY EARLY THIS EVENING AND TRIGGER ANOTHER ROUND OF CONVECTION...TIMED MUCH LIKE PAST FEW EVENTS MAINLY AT NIGHT. MCS SHOULD THEN PUSH TO THE SOUTH AND EAST DIMINISHING POPS OVERNIGHT. CONFIDENCE IN THIS SCENARIO IS SOMEWHAT LOW HOWEVER AS CURRENT MCS CONTINUES TO BACK BUILD ACROSS SRN NE. FORECASTING EVENTUAL POSITION OF SYNOPTIC AND/OR MESOSCALE BOUNDARIES WILL BE DIFFICULT. BY FRI MODEL CONSENSUS SUGGESTS A RELATIVE LULL WITH IA IN FAIRLY WEAK SELY SURFACE FLOW. STILL UNSTABLE BUT LITTLE FOCUS. ATTENTION TURNS TO THE WEST AGAIN EYING RESPONSE TO GRADUALLY APPROACHING WRN TROUGH. THIS WILL LEAD TO INCREASING WARM ADVECTION AND BAROCLINICITY THROUGH SIOUXLAND MO VALLEY REGION. 305K FLOW IS FAIRLY WEAK SO DO NOT EXPECT SIGNIFICANT MCS BUT INCREASING POPS. CONVECTION MAY BE MORE SIGNIFICANT BY SAT NIGHT AND SUNDAY HOWEVER AS FLOW AND ASSOCIATED THETA-E ADVECTION INCREASE. KINEMATIC FORCING WILL INCREASE AS WELL AS LOBE OF UVM PUSHES ACROSS NRN PLAINS INTO EARLY SUN WHICH IS ALSO FOCUSED BY PASSAGE OF INVERTED SURFACE TROUGH. THIS ALL LEADS TO POPS BACK UP INTO LIKELIES DURING THIS PERIOD. BY EARLY NEXT WEEK PATTERN WILL SHIFT SUFFICIENTLY TO LOWER OUR PRECIP CHANCES AND COOL TEMPS SOMEWHAT AS IA ENDS UP IN NWLY SURFACE FLOW. THIS RESULTS IN EXTENDED FORECAST EITHER DRY OR WITH ONLY SLIGHT CHANCES AND MAXES ONLY IN THE 60S OR POSSIBLY LOWER 70S. && .AVIATION...03/12Z CONVECTION DIMINISHING ACROSS CENTRAL IOWA THIS MORNING WITH GRAVITY WAVE CAUSING SOME GUSTY WINDS ACROSS NORTHERN IOWA. WINDS SHOULD SHIFT AROUND TO THE SOUTH ONCE RAIN/TSRA DIMINISH AND BUFR SOUNDINGS HAVE ENOUGH MIXING TO WARRANT GUSTS IN THE UPPER TEENS THROUGH THE DAY. LOW CONFIDENCE WITH TIMING OF CONVECTION THIS AFTERNOON/EVENING...AND ONLY HAVE VCTS MENTIONED AT OTM/DSM ATTM WITH THE BOUNDARY DRIFTING SOUTH. DECENT CHANCE FOR SOME FOG DEVELOPMENT OVERNIGHT INTO FRIDAY MORNING AND HAVE MVFR VIS MENTION FOR ALL TAF SITES EXCEPT DSM. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...KLP LONG TERM...BSS AVIATION...KLP
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 621 AM CDT THU MAY 3 2012 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- 621 AM CDT THU MAY 3 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR MUCH OF CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS BELOW SEVERE LIMITS WILL AFFECT CENTRAL AND EASTERN IOWA EARLY THIS MORNING. ADDITIONAL THUNDERSTORMS MAY DEVELOP LATER THIS AFTERNOON AND TONIGHT AS WELL WITH THE BEST POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS OVER CENTRAL AND SOUTHERN IOWA INTO THE EVENING. LOCALLY HEAVY RAINS AND FLASH FLOODING ARE ALSO POSSIBLE. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY OUR RECENT ACTIVE WEATHER PATTERN WILL CHANGE LITTLE THROUGH THE WEEKEND WITH OFF AND ON CHANCES FOR THUNDERSTORMS. A FEW OF THESE STORMS MAY STILL BE SEVERE WITH LARGE HAIL AND DAMAGING WINDS THE PRIMARY THREATS. LOCALLY HEAVY RAINS AND FLASH FLOODING REMAIN POSSIBLE AS WELL. OTHER LESSER THUNDERSTORM CHANCES ARE IN THE FORECAST EARLY NEXT WEEK...BUT THE POTENTIAL FOR SEVERE WEATHER APPEARS LOW AT THIS TIME. .SPOTTER INFORMATION STATEMENT... A FEW EPISODES OF SPOTTER ACTIVATION MAY BE NEEDED THROUGH THE WEEKEND. SMALL
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 451 AM CDT THU MAY 3 2012 IAZ037-038-031015- GRUNDY-HARDIN- 451 AM CDT THU MAY 3 2012 ...STRONG THUNDERSTORM TO AFFECT PORTIONS OF NORTH CENTRAL IOWA... AT 448 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER CENTRAL HARDIN COUNTY...MOVING NORTHEAST AT 40 MPH. ONE HALF INCH DIAMETER HAIL...WINDS UP TO 50 MPH...CONTINUOUS CLOUD TO GROUND LIGHTNING...BRIEF MODERATE DOWNPOURS...ARE POSSIBLE WITH THIS STORM THROUGH 515 AM CDT. LOCATIONS IMPACTED INCLUDE... ELDORA... STEAMBOAT ROCK... ACKLEY... WELLSBURG... GUSTY WINDS MAY CAUSE SMALL BRANCHES TO BE BLOWN DOWN...AND LOOSE OBJECTS 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 503 AM CDT THU MAY 3 2012 IAZ016-017-025>027-031100- BUTLER-CERRO GORDO-FRANKLIN-HANCOCK-WRIGHT- 503 AM CDT THU MAY 3 2012 ...STRONG THUNDERSTORM TO AFFECT NORTH CENTRAL THROUGH THE EARLY MORNING... AT 457 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER WEST CENTRAL FRANKLIN COUNTY...MOVING EAST AT 45 MPH. ONE HALF INCH DIAMETER HAIL...WINDS UP TO 50 MPH...CONTINUOUS CLOUD TO GROUND LIGHTNING...BRIEF MODERATE DOWNPOURS...ARE POSSIBLE WITH THIS STORM THROUGH 6 AM CDT. LOCATIONS IMPACTED INCLUDE... SHEFFIELD... HAMPTON... GENEVA... ROCKWELL... HANSELL... DUMONT... DOUGHERTY... AREDALE... APLINGTON... PARKERSBURG... BRISTOW... ALLISON... GREENE... CLARKSVILLE... GUSTY WINDS MAY CAUSE SMALL BRANCHES TO BE BLOWN DOWN...AND LOOSE OBJECTS TO BLOW AROUND. STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS TREES. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. PODRAZIK
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
509 AM CDT THU MAY 03 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0345 AM TSTM WND GST 2 WNW CLARION 42.75N 93.77W
05/03/2012 M61 MPH WRIGHT IA AWOS
MEASURED AT CLARION AIRPORT
&&
SMALLSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 525 AM CDT THU MAY 3 2012 IAZ006-007-016-017-024>028-035>039-031300- WINNEBAGO-WORTH-HANCOCK-CERRO GORDO-HUMBOLDT-WRIGHT-FRANKLIN- BUTLER-BREMER-WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK- INCLUDING THE CITIES OF...FOREST CITY...NORTHWOOD...GARNER... MASON CITY...HUMBOLDT...CLARION...HAMPTON...ALLISON...WAVERLY... FORT DODGE...WEBSTER CITY...ELDORA...GRUNDY CENTER...WATERLOO 525 AM CDT THU MAY 3 2012 ...STRONG GUSTY NON THUNDERSTORM WINDS TO AFFECT NORTH CENTRAL IOWA... STRONG WEST WINDS BEHIND A LINE OF THUNDERSTORMS WILL AFFECT NORTH CENTRAL IOWA THROUGH 8 AM CDT THIS MORNING. SUSTAINED WINDS OF 30 TO 40 MPH WITH HIGHER GUSTS TO NEAR 50 MPH ARE POSSIBLE...GENERALLY ALONG AND NORTH OF HIGHWAY 20 EAST OF FORT DODGE TO WATERLOO. THESE WINDS ARE NOT ASSOCIATED WITH ANY THUNDERSTORMS. KLP
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
540 AM CDT THU MAY 03 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0530 AM TSTM WND GST 4 NNW SWALEDALE 43.03N 93.34W
05/03/2012 M58 MPH CERRO GORDO IA MESONET
IDOT RWIS SITE ALONG INTERSTATE 35 SOUTHWEST OF MASON
CITY.
&&
SMALLPRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DES MOINES IA
639 AM CDT THU MAY 03 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0338 AM TSTM WND DMG 1 SE YETTER 42.31N 94.84W
05/03/2012 CALHOUN IA TRAINED SPOTTER
LARGE HEALTHY MAPLE TREE DOWN IN YARD...ROUGHLY 3 FEET IN
DIAMETER. TIME ESTIMATED BY RADAR.
0352 AM TSTM WND GST 4 NNW ROCKWELL CITY 42.45N 94.66W
05/03/2012 M58.00 MPH CALHOUN IA MESONET
IDOT RWIS SITE. TIME ESTIMATED.
0359 AM TSTM WND GST 3 SSE SOMERS 42.34N 94.41W
05/03/2012 M60.00 MPH CALHOUN IA MESONET
MEASURED AT KCCI TV FARNHAMVILLE/PRAIRIE CITY SCHOOLNET
SITE.
0445 AM TSTM WND GST 2 WNW CLARION 42.75N 93.77W
05/03/2012 M61.00 MPH WRIGHT IA AWOS
MEASURED AT CLARION AIRPORT
0530 AM TSTM WND GST 4 NNW SWALEDALE 43.03N 93.34W
05/03/2012 M58.00 MPH CERRO GORDO IA MESONET
IDOT RWIS SITE ALONG INTERSTATE 35 SOUTHWEST OF MASON
CITY.
&&
SMALLThe national radar mosaic for the moment the first event began.
2 high wind. Local standard time, as filed.
Winds of 60 MPH along with a heat burst.
Heat burst. The winds blew down a grain bin near Leighton.
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, May 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: 368834, 368835.