Severe thunderstorms developed rapidly during the late morning and afternoon along and behind a slow moving cold front. These thunderstorms initially developed over Minnesota and then moved southeast into northeast Iowa where they produced large hail and some wind damage.
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 ARX wrote it up.
Severe thunderstorms developed rapidly during the late morning and afternoon along and behind a slow moving cold front. These thunderstorms initially developed over Minnesota and then moved southeast into northeast Iowa where they produced large hail and some wind damage. The largest hail reported was 1.75 inches in Ridgeway (Winneshiek County) before the storms became wind dominated. Trees were blown down or uprooted from Hesper (Winneshiek County) east through Waukon (Allamakee County) including a 65 mph gust near Calmar (Winneshiek County). 7 calves were killed when an almost 100 year old barn was blown down near Dorchester (Allamakee County).
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 La Crosse, WI wrote its last area forecast discussion before the first event at Jul 18, 11:40 AM CST, 1 hour 55 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 1240 PM CDT WED JUL 18 2012 .SHORT TERM... 1117 AM CDT WED JUL 18 2012 HAVE BEEN ASSESSING INFORMATION THIS MORNING AND HAVE BEEN WORKING ON INCREASING THE RAIN AND STORM CHANCES. CONFIDENCE IS INCREASING... BUT STILL MODERATE ON THE OUTCOMES OF THIS AFTERNOON AND EVENING. WATCHING SOME KEY FEATURES INCLUDING THE SHORTWAVE TROUGH OVER THE DAKOTAS WITH A LOCAL TIGHT CIRCULATION OVER KFSD RIGHT NOW PER GOES WATER VAPOR AND SOME RADAR ECHO...HEADING TOWARD THE AREA. THE MINNEAPOLIS CONVECTION AND NW-SE ARM OF THUNDER IS ALONG A FRONTOGENETIC AREA IN THE 925-800MB LAYER AND THIS FORCING CONTINUES...PER LATEST RAP/NAM TO REMAIN STATIONARY INTO THE EVENING. WITH MU CAPE BUILDING AHEAD OF THE SYSTEM...THINK THE RISK OF SEVERE WIND ACROSS CLARK-TAYLOR HAS INCREASED. IN ANY CASE...RAIN SHOULD CONTINUE FOR MOST OF THE AFTERNOON UP THERE TOO. SPC HAS UPGRADED THE AREA TO A SLIGHT RISK OF STORMS AND WITH SHORTWAVE ENERGY AND DYNAMICS COMING IN...MAIN CONCERN FOR SEVERE WEATHER WOULD BE WIND. BY AFTERNOON AS THE KFSD MID-LEVEL WAVE APPROACHES AND CONVERGENCE INCREASES WITH INSTABILITY BUILDING ACROSS THE SOUTH IN VICINITY OF THE WARM/STATIONARY SURFACE FRONT AND COLD FRONTAL INVERTED TROUGH IN THE WESTERN FORECAST AREA...SUSTAINED UPDRAFTS ARE LIKELY. THIS WOULD CONGEAL INTO A COLD POOL AND WITH STEEP LOW-LEVEL LAPSE RATES...WIND GUSTS IN THE 40-60 MPH RANGE ARE POSSIBLE. SO THE THOUGHT IS STRONG-SEVERE STORMS SOUTH OF CURRENT ACTIVITY IN WI...IN THE 3-9PM TIME FRAME. THE MINNEAPOLIS SYSTEM SEEMS POISED TO MOVE DOWN THE FRONTOGENETIC AXIS AND CAUSE SOME WARNINGS THIS AFTERNOON IN WI. THIS WOULD MAINLY AFFECT CLARK AND TAYLOR COUNTIES. WITH MU CAPE INCREASING THERE /ABOUT 2K J/KG AT 11AM/...AND A BIT BETTER SHEAR...WE MAY SEE A LINE WITH DAMAGING WIND BY EARLY-MID AFTERNOON. COULD SEE 2-3 INCHES OF RAIN TOO. WILL ALSO BE INCREASING THE RAIN CHANCES TONIGHT TO ACCOUNT FOR LATE AFTERNOON WEATHER TO SHIFT ACROSS THE FORECAST AREA. MAIN ACTIVE PERIOD APPEARS TO BE 00-03Z. MORE TO COME IN LATER DISCUSSION. .LONG TERM...SATURDAY THROUGH TUESDAY 334 AM CDT WED JUL 18 2012 18.00Z MEDIUM RANGE MODELS IN REASONABLY GOOD AGREEMENT FOR THE SAT THRU TUE PERIOD. SHORTWAVES MOVING ACROSS CENTRAL/SOUTHERN CAN FLATTEN THE MID NOAM RIDGING SAT. BY SUN/MON THE MID LEVEL RIDGE AXIS REBUILDS FURTHER WEST OVER MT/WY/DAKOTAS INTO ALB/SASKAT... LEAVING THE UPPER MIDWEST UNDER BROAD NORTHWEST FLOW ALOFT. THE NORTHWEST FLOW BY SUN/MON ALLOWS THE PASSING SHORTWAVES TO PUSH TO A COLD FRONT/SFC TROUGH SOUTHEAST INTO/ACROSS THE AREA LATER IN THE WEEKEND AND FOR EARLY NEXT WEEK. PLENTY OF DETAIL DIFFERENCES WITH LOWER LEVEL MOISTURE...CAPE AND THERMO-DYNAMIC FORCING MECHANISMS IN THE SUN-TUE TIME-FRAME...BUT IMPROVED MODEL CONSISTENCY AND LARGER SCALE SIGNAL SUPPORTS 20-35 PERCENT SHRA/TSRA CHANCES IN THESE TIME PERIODS. WITH GENERAL SOUTHWEST/WEST LOW/MID LEVEL FLOW...MODEL CONSENSUS OF TEMPS REMAINING ABOVE NORMAL IN THE DAY 4-7 PERIOD LOOKS GOOD AS WELL. && .AVIATION...THROUGH 18Z THURSDAY 1240 PM CDT WED JUL 18 2012 WATER VAPOR IMAGERY SHOWING A TROUGH OF LOW PRESSURE OVER THE DAKOTAS/NEBRASKA...MOVING EAST TOWARD THE AREA. LIFT AHEAD OF THIS WAVE EXPECTED TO KICK OFF/INCREASE CONVECTION ACROSS THE AREA THROUGH THIS AFTERNOON AND INTO THIS EVENING. SOME OF THIS CONVECTION COULD BECOME STRONG TO SEVERE BETWEEN 3 PM AND 8 PM GENERALLY ALONG AND SOUTH OF I-90 ACROSS MINNESOTA INTO WISCONSIN. DAMAGING WIND WOULD BE THE MAIN THREAT. LOOKING FOR A GENERAL DECREASE IN SHRA/TS COVERAGE AFTER MIDNIGHT AS THE TROUGH AXIS SHIFTS EAST OF THE AREA. HOWEVER...SOME LINGERING SHRA/TS EXPECTED TO CONTINUE AFTER MIDNIGHT WITH FAIRLY STEEP LAPSE RATES STILL OVERHEAD. MODELS THEN INDICATE BROKEN DECK OF MVFR CLOUD AFTER 09Z AS THE BOUNDARY LAYER COOLS BEHIND THE DEPARTING WAVE. EXPECTING THIS MVFR CLOUD COVER TO LINGER THROUGH THURSDAY MORNING..THEN SCOURING OUT BY AFTERNOON AS HIGH PRESSURE BUILDS IN. && .ARX WATCHES/WARNINGS/ADVISORIES... 334 AM CDT WED JUL 18 2012 WI...NONE. MN...NONE. IA...NONE. && SHORT TERM...BAUMGARDT/SCHMIDT LONG TERM....RRS AVIATION...DAS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LA CROSSE WI 1244 PM CDT WED JUL 18 2012 WIZ017-029-191100- CLARK-TAYLOR- 1244 PM CDT WED JUL 18 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF NORTH CENTRAL WISCONSIN. .DAY ONE...THIS AFTERNOON AND TONIGHT SCATTERED THUNDERSTORMS WILL CONTINUE INTO THIS EVENING. BESIDES PERIODIC HEAVY RAIN...A FEW STRONGER STORMS COULD PRODUCE GUSTY WIND AS THEY MOVE THROUGH. LOCALIZED RAINFALL COULD ALSO REACH 1 TO 1.5 INCHES DEPENDING ON HOW THE STORMS TRACK. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY ADDITIONAL THUNDERSTORMS COULD BE IN THE AREA EARLY ON THURSDAY BUT THE SEVERE WEATHER RISK DOES NOT LOOK FAVORABLE. THERE ARE ALSO SMALL THUNDERSTORM CHANCES FROM THE WEEKEND INTO EARLY NEXT WEEK BUT THE RISK OF ANY WIDESPREAD SEVERE WEATHER LOOKS LOW. .SPOTTER INFORMATION STATEMENT... WIDESPREAD SPOTTER ACTIVATION IS NOT LOOKING FAVORABLE BUT ANY REPORTS OF HAIL OR GUSTY WINDS...IN ADDITION TO RAINFALL TOTALS... WOULD BE APPRECIATED. .EMERGENCY MANAGEMENT COORDINATION... NO WEBINAR IS SCHEDULED. IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ032>034-041>044- 053>055-061-191100- ADAMS-ALLAMAKEE-BUFFALO-CHICKASAW-CLAYTON-CRAWFORD-DODGE-FAYETTE- FILLMORE-FLOYD-GRANT-HOUSTON-HOWARD-JACKSON-JUNEAU-LA CROSSE- MITCHELL-MONROE-MOWER-OLMSTED-RICHLAND-TREMPEALEAU-VERNON-WABASHA- WINNESHIEK-WINONA- 1244 PM CDT WED JUL 18 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF SOUTHEAST MINNESOTA...NORTHEAST IOWA...AND SOUTHWEST INTO CENTRAL WISCONSIN. .DAY ONE...THIS AFTERNOON AND TONIGHT HOT TEMPERATURES WILL IMPACT MAINLY NORTHEAST IOWA AND NEIGHBORING AREAS WITH HEAT INDEX READINGS IN THE 95 TO 105 RANGE INTO THE EVENING. PRECAUTIONS FOR HEAT SHOULD BE USED. THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER PARTS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA THIS AFTERNOON...AND COULD SPREAD MORE INTO WESTERN WISCONSIN BY EVENING. STORMS HAVE A THREAT FOR LOCALLY HEAVY RAIN...HAIL AND DAMAGING WINDS INTO TONIGHT. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THERE COULD BE LINGERING THUNDERSTORMS EARLY THURSDAY BUT SEVERE WEATHER IS NOT EXPECTED AT THIS TIME. THERE ARE ALSO SMALL STORM CHANCES THIS WEEKEND INTO EARLY NEXT WEEK BUT THE OVERALL RISK OF WIDESPREAD SEVERE WEATHER APPEARS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED AT TIMES THIS AFTERNOON AND INTO THE EVENING. PEAK WIND GUSTS OR ANY OBSERVED DAMAGE REPORTS WOULD BE USEFUL...IN ADDITION TO HAIL OR RAINFALL TOTALS. .EMERGENCY MANAGEMENT COORDINATION... NO WEBINAR IS SCHEDULED. SHEA
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
102 PM CDT WED JUL 18 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1258 PM HAIL HAYFIELD 43.89N 92.85W
07/18/2012 M1.50 INCH DODGE MN TRAINED SPOTTER
&&
TMSPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
154 PM CDT WED JUL 18 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0151 PM HAIL 2 NE DEXTER 43.74N 92.67W
07/18/2012 M0.88 INCH MOWER MN TRAINED SPOTTER
&&
DAVISPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
159 PM CDT WED JUL 18 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0158 PM TSTM WND GST 1 W GRAND MEADOW 43.71N 92.59W
07/18/2012 E50 MPH MOWER MN TRAINED SPOTTER
&&
DAVISSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LA CROSSE WI 206 PM CDT WED JUL 18 2012 IAZ008>010-018-019-MNZ094>096-182030- CHICKASAW-FILLMORE-FLOYD-HOUSTON-HOWARD-MITCHELL-MOWER-WINNESHIEK- 206 PM CDT WED JUL 18 2012 ...THUNDERSTORMS EXPECTED THIS AFTERNOON... THUNDERSTORMS WILL BECOME MORE NUMEROUS THIS AFTERNOON AND COULD BECOME SEVERE AT TIMES. BESIDES A HEAVY RAIN AND LIGHTNING THREAT... HAIL AND GUSTY WINDS ARE EXPECTED WITH STRONGER STORMS. MOVE INDOORS WHEN STORMS APPROACH AND DO NOT TAKE CHANCES WITH LIGHTNING. IF A WARNING IS ISSUED FOR YOUR AREA...STAY AWAY FROM TREES AND WINDOWS. A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 8 PM. SHEA
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
229 PM CDT WED JUL 18 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0227 PM HAIL 1 S RACINE 43.76N 92.48W
07/18/2012 E0.75 INCH MOWER MN TRAINED SPOTTER
DIME SIZED HAIL
&&
ADAMSPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
230 PM CDT WED JUL 18 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0227 PM TSTM WND GST 1 S RACINE 43.76N 92.48W
07/18/2012 E50 MPH MOWER MN TRAINED SPOTTER
&&
ADAMSThe La Crosse radar (KARX), 90 km away, was scanning. The volume nearest the first event began at 19:33 UTC.
7 thunderstorm wind, 3 heavy rain, 2 hail, 1 flood. Local standard time, as filed.
Numerous streets were flooded in Cresco and the water was deep enough in the downtown area to go over the curbs and threatened to go into some businesses. The flooding was produced by 2.65 inches of rain that fell in an hour and a half.
In an hour, 1.5 inches of rain fell in Decorah.
Golf ball sized hail fell in Ridgeway.
Trees were blown down in Hesper.
Several trees were uprooted and corn in the area was bent over from the winds south of Highlandville.
A machine shed was blown down and across Twin Springs Road just southwest of Decorah.
A large tree was uprooted just north of Decorah.
In an hour, 1.75 inches of rain fell in Burr Oak.
A wind gust of 65 mph occurred north of Calmar.
A barn was destroyed by winds near Dorchester killing 7 calves that were inside the barn.
Some trees and power lines were blown down in West Union.
In a half hour, 1.75 inches of rain fell in Monona.
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, July 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: 400415, 394578, 394569, 394570, 394571, 394572, 395350, 394574, 394774, 394575, 394576, 394577, 394770.