Large-scale atmospheric lift and wind shear associated with a short wave trough combined with an unstable air mass over the region to produce rotating thunderstorms that produced large hail over southern Wisconsin during the afternoon hours of July 23rd.
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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 MKX wrote it up.
Large-scale atmospheric lift and wind shear associated with a short wave trough combined with an unstable air mass over the region to produce rotating thunderstorms that produced large hail over southern Wisconsin during the afternoon hours of July 23rd.
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 Milwaukee, WI wrote its last area forecast discussion before the first event at Jul 23, 3:12 AM CST, 8 hours 8 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 412 AM CDT THU JUL 23 2009 FORECAST FOCUS ON FOG AND PRECIPITATION CHANCES TODAY...SEVERE WEATHER POTENTIAL ON FRIDAY AND FRIDAY NIGHT. LATEST WATER VAPOR IMAGERY INDICATED AN UPPER TROUGH EXTENDING FROM SOUTH CENTRAL CANADA INTO WISCONSIN AND LOWER MICHIGAN. A VORTICITY MAXIMUM EMBEDDED IN THE TROUGH OVER WEST CENTRAL AND SOUTHWEST WISCONSIN WAS HELPING DRIVE SOME SHOWERS ACROSS MARQUETTE AND GREEN LAKE COUNTIES. THESE HAVE SHOWN A DIMINISHING TREND IN THE LAST HALF HOUR. PATCHY FOG WAS ALSO OBSERVED ACROSS THE AREA...WITH AREAS OF DENSE FOG IN THE WISCONSIN RIVER VALLEY. .TODAY AND TONIGHT...WILL MENTION DIMINISHING SHOWERS IN A PRE FIRST PERIOD OF THE FORECAST. THESE SHOWERS HAD BEEN BUILDING SOUTHEAST INTO AN AREA OF UP TO 150 J/KG OF 0-3KM CAPE AND LITTLE TO NO CIN. HOWEVER...SOUTHEAST MOVEMENT ON GRADIENT OF THIS INSTABILITY...AND SHOWERS SHOULD CONTINUE TO DIMINISH BY 12Z THURSDAY. ANY LINGERING FOG SHOULD MIX OUT BY 14Z ACROSS THE AREA AS WELL. VARIOUS WEAK VORTICITY MAXIMA ROTATING THROUGH THE AREA THIS AFTERNOON SHOULD COMBINE WITH WEAK INSTABILITY TO BRING CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS. DESPITE PARTLY SUNNY SKIES...TEMPERATURES ARE EXPECTED TO REMAIN IN THE 70S FOR HIGHS. LAKE BREEZE SHOULD ALSO FORM THIS AFTERNOON NEAR THE SHORE GIVEN LIGHT GRADIENT WINDS. A QUIET NIGHT IS EXPECTED TONIGHT...AS WARM AIR ADVECTION BEGINS ACROSS THE AREA. PARTLY CLOUDY SKIES AND SEASONABLE TEMPERATURES ARE EXPECTED. .FRIDAY AND FRIDAY NIGHT...MODELS BRING COLD FRONT INTO NORTHWEST WISCONSIN BY 00Z SATURDAY...THEN SOUTHEAST ACROSS THE AREA BY 12Z SATURDAY. WARM FRONT ALSO EXTENDS ACROSS THE SOUTHWEST COUNTIES DURING THIS TIME...AS SURFACE LOW DEVELOPS ALONG THE FRONT BEFORE MOVING EASTWARD. DEEPENING UPPER LOW ALSO MOVES INTO THE REGION MAINLY FRIDAY NIGHT. SOME QUESTION AS TO HOW MUCH CAPE WILL BE AVAILABLE FOR POSSIBLE CONVECTION AHEAD OF THE COLD FRONTAL PASSAGE. WARM AIR ADVECTION CONTINUING INTO FRIDAY SHOULD HELP DEVELOP SOME SHOWERS AND STORMS ACROSS THE AREA. THIS WILL LIMIT THE DAYTIME HEATING ACROSS THE AREA. MODELS HAVING A TOUGH TIME GENERATING MEAN LAYER CAPE WITH DECENT 0-3KM LAYER CAPE. MOST OF THE 1000 TO 1500 J/KG OF MEAN LAYER CAPE IS ELEVATED IN NATURE FRIDAY AND FRIDAY NIGHT. GIVEN THIS UNCERTAINTY...DECIDED TO PULL SEVERE MENTION FROM THE FORECAST UNTIL BETTER GRASP ON CAPE IS ATTAINED. IF GOOD DAYTIME HEATING AND SUBSEQUENT LOW LEVEL CAPE IS ATTAINED...DEEP LAYER 0-6KM SHEAR VALUES OF 35 TO 40 KNOTS WITH STRONG TURNING IN THE LOW LEVELS WOULD CERTAINLY POINT TO A SEVERE RISK. .SATURDAY...CORE OF UPPER LOW PASSES JUST NORTH OF THE AREA ON SATURDAY. FORECAST SOUNDINGS SHOW WEAK INSTABILITY BY AFTERNOON ONCE AGAIN...SO KEPT MENTION OF SHOWERS AND ISOLATED STORMS IN THE FORECAST FOR SATURDAY AFTERNOON. COOLER TEMPERATURES SHOULD RETURN WITH THE UPPER LOW NEARBY. .SATURDAY NIGHT THROUGH WEDNESDAY...UPPER LOW SHIFTS NORTHEAST INTO CANADA...THEN IS ABSORBED BY A MORE LONGWAVE TYPE TROUGH OVER SOUTH CENTRAL CANADA. THIS SHOULD KEEP THE REGION IN BROAD CYCLONIC FLOW DURING THIS PERIOD...AND SHOULD SHIFT SEVERAL VORTICITY MAXIMA THROUGH THE AREA. KEPT POPS NEARLY THE SAME FROM PREVIOUS FORECAST FOR THIS PERIOD. TEMPERATURES SHOULD CONTINUE TO BE ON THE COOL SIDE. && .AVIATION...AREAS OF RADIATIONAL FOG ARE OCCURRING EARLY THIS AM WITH WIDE RANGING VSBYS FROM VFR TO VLIFR ACROSS SRN WI. VLIFR CIGS ARE ASSOCIATED WITH THE DENSE FOG AS WELL. FOG SHOULD MAINLY LIFT BY 1400 UTC. A LINE OF SHOWERS OVER GREEN LAKE AND FAR NRN COLUMBIA COUNTY IS EXPECTED TO CONTINUE TO MOVE ESEWD AND WEAKEN. THE OUTFLOW FROM THESE SHOWERS STILL MAY PRODUCE ENOUGH LIFT TO CONTINUE ISOLD SHOWERS THROUGH THE AM NORTH OF INTERSTATE 94. UNSTABLE CONDITIONS WILL INCREASE FOR THIS AFTERNOON AND EARLY EVENING DUE TO DAYTIME HEATING WITH SCT SHOWERS AND ISOLD TSTORMS EXPECTED TO REDEVELOP ONCE AGAIN. THEY SHOULD BE MOST FOCUSED IN ERN WI NEAR THE LAKE BREEZE FRONT. BASES OF CUMULUS CLOUDS TODAY SHOULD REMAIN MAINLY VFR WITH LOCALLY MVFR CIGS POSSIBLE. NO FOG EXPECTED TNT AS LGT SWLY WINDS DEVELOP AHEAD OF APPROACHING CANADIAN LOW PRESSURE FROM THE NW. STRONG WARM ADVECTION FROM APPROACHING LOW AND PASSAGE OF COLD FRONT WILL BRING SHOWERS AND TSTORMS TO SRN WI FROM FRI AFTERNOON THROUGH THE NIGHT. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...NONE. && SHORT/LONG TERM...08/WOOD AVIATION/MARINE...20/GEHRING
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 940 AM CDT THU JUL 23 2009 WIZ046-047-051-052-056>060-062>072-241030- MARQUETTE-GREEN LAKE-FOND DU LAC-SHEBOYGAN-SAUK-COLUMBIA-DODGE- WASHINGTON-OZAUKEE-IOWA-DANE-JEFFERSON-WAUKESHA-MILWAUKEE- LAFAYETTE-GREEN-ROCK-WALWORTH-RACINE-KENOSHA- 940 AM CDT THU JUL 23 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL WISCONSIN...SOUTH CENTRAL WISCONSIN AND SOUTHEAST WISCONSIN. .DAY ONE...TODAY AND TONIGHT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP ONCE AGAIN THIS AFTERNOON. THE THUNDERSTORMS SHOULD REMAIN BELOW SEVERE LIMITS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FRIDAY AFTERNOON AND NIGHT WEST OF A LINE FROM WISCONSIN DELLS TO COLUMBUS TO BELOIT AS A WARM FRONT APPROACHES THE REGION. A COLD FRONT WILL FOLLOW THE WARM FRONT LATE FRIDAY NIGHT. ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE FROM THE WEEKEND INTO EARLY NEXT WEEK. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT. LMZ643>646-241030- SHEBOYGAN TO PORT WASHINGTON WI- PORT WASHINGTON TO NORTH POINT LIGHT WI- NORTH POINT LIGHT TO WIND POINT WI- WIND POINT WI TO WINTHROP HARBOR IL- 940 AM CDT THU JUL 23 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP ONCE AGAIN THIS AFTERNOON. THE THUNDERSTORMS SHOULD REMAIN BELOW SEVERE LIMITS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THUNDERSTORMS ARE LIKELY FRIDAY NIGHT AS A WARM FRONT MOVES INTO THE REGION. A COLD FRONT WILL FOLLOW THE WARM FRONT LATE FRIDAY NIGHT. ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE FROM THE WEEKEND INTO EARLY NEXT WEEK. KAPELA WWW.WEATHER.GOV/MKX
The Milwaukee radar (KMKX), 54 km away, was scanning. The volume nearest the first event began at 17:20 UTC.
4 hail, 2 lightning. Local standard time, as filed.
Lightning struck an Alliant Energy electrical substation, blowing out a circuit. About 800 customers went without power for about one hour.
A 44-year-old woman was struck by lightning while standing in the doorway of a barn holding the reins of a horse. She was taken to Beloit Memorial Hospital and treated in the emergency department.
Hail up to 1 inch in diameter covered the ground white near the intersection of State Highway 22 and Grouse Avenue near Montello. Gusty winds also brought down small tree branches.
Hail, estimated to be 1 inch in diameter, fell in a 2-mile wide swath from southwest of North Cape to north of Union Grove.
The public reported that hail, estimated to be 3/4 inch in diameter and driven by gusty thunderstorm winds, damaged corn crops in northeast Walworth County.
Hail, estimated to be 1 inch in diameter, fell in a 2-mile wide swath from 1.5 miles east of Silver lake to 2 miles south of Bristol in Kenosha County.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2009Every state in 2009This day in weather historyWarnings in Wisconsin, July 2009
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: 189195, 189196, 189191, 189192, 189194, 189193.