High winds produced by an outflow from a thunderstorm uprooted trees near Neillsville and Willard in Clark County.
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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 ARX wrote it up.
High winds produced by an outflow from a thunderstorm uprooted trees near Neillsville and Willard in Clark 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 May 9, 2:54 AM CST, 10 hours 6 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 354 AM CDT MON MAY 9 2011 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT MAIN FORECAST CONCERN IS TRYING TO FIGURE OUT ANY PRECIPITATION DETAILS THROUGH THE SHORT TERM. CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED DEEP TROUGHING OVER THE WESTERN U.S. AND RIDGING DOWNSTREAM OVER THE ENTIRE MISSISSIPPI RIVER VALLEY. PROFILER DATA AT 850MB SHOWED STRONG ADVECTION OCCURRING WITH SOUTH TO SOUTHWEST WINDS OF 45-60 KT FROM EASTERN TEXAS NORTHWARD INTO SOUTHERN MINNESOTA. A COMBINATION OF 3.9 UM SATELLITE IMAGERY AND RUC 850MB DEWPOINT ANALYSES DEPICT A POOL OF LOW LEVEL MOISTURE OVER THE CENTRAL PLAINS ADVECTING NORTH AND NORTHEAST WITH THE LOW LEVEL JET. RIGHT NOW THE EDGE OF THE MOISTURE RUNS FROM SOUTHWEST MINNESOTA TO DES MOINES. WITHIN THE POOL OF LOW LEVEL MOISTURE...THE RUC SUGGESTS 850MB DEWPOINTS AROUND 12C...COMPARED TO 0 TO -4C OVER THE FORECAST AREA. SURFACE DEWPOINTS ALSO QUITE HIGH IN THE MOISTURE POOL WITH READINGS IN THE MID 60S. THE EDGE OF THE MOISTURE ALSO DEPICTS WARMER AIR. 00Z RAOBS HAD 850MB TEMPS OF 11C AT MPX AND DVN...BUT AROUND 18C AT OAX AND TOP. ON THE NOSE OF THE MOISTURE POOL AND LOW LEVEL JET...AN AREA OF CONVECTION WAS CROSSING WESTERN MINNESOTA. THERE IS ALSO AN MCV EVIDENT OVER EASTERN SOUTH DAKOTA...MOVING EAST-NORTHEAST. AT THE SURFACE...LOW PRESSURE WAS EVIDENT NEAR OGALLALA NEBRASKA WITH A WARM FRONT SORT OF EXTENDING SOUTHEAST INTO NORTHERN MISSOURI. TODAY AND TONIGHT...TROUGHING OVER THE WESTERN U.S. WILL ONLY MIGRATE SLOWLY EAST DURING THE NEXT 24 HOURS. HOWEVER...THERE DOES APPEAR TO BE A FAIRLY POTENT WAVE EJECTING OUT OF THE TROUGH TONIGHT WHICH REACHES NORTHEAST WYOMING AT 12Z TUESDAY. THIS SHORTWAVE WILL HELP TO LIFT THE SURFACE WARM FRONT IN NORTHERN MISSOURI AT LEAST TO I-80 BY 12Z TUESDAY...IF NOT SLIGHTLY FARTHER NORTH. MAIN ISSUE THROUGH TONIGHT IS THE IMPACT OF THE CURRENT WARM ADVECTION PATTERN ON POTENTIAL PRECIPITATION. THERE ARE INDICATIONS OF ELEVATED SHOWERS AND THUNDERSTORMS DEVELOPING THIS MORNING ON THE EDGE OF THE MOISTURE POOL IN IOWA...ASSOCIATED WITH ISENTROPIC LIFT ON THE 305K SURFACE. THE 08.05Z AND MANY PREVIOUS HRRR RUNS AS WELL AS THE 09.00Z CANADIAN ALL SHOW THIS. MEANWHILE...ANTICIPATING THAT THE SHOWERS AND THUNDERSTORMS IN WESTERN MINNESOTA...BEING AIDED BY THE MCV AND LOW LEVEL JET...WILL CONTINUE EAST OR EAST-NORTHEAST THROUGH THE MORNING. ALL SHOWERS AND THUNDERSTORMS WOULD THEN DIMINISH DURING THE AFTERNOON WITH THE LOSS OF THE NOCTURNAL LOW LEVEL JET. TONIGHT...AM CONCERNED THAT WE MAY NOT HAVE MUCH CHANCE FOR CONVECTION...DESPITE THE SURFACE WARM FRONT APPROACHING. ALTHOUGH THE 09.00Z NAM DEVELOPS CONVECTION OVER THE AREA AND SLIDES IT SOUTH...MOST MODELS HAVE 700MB TEMPS AT 10C OR HIGHER AT 00Z SOUTH OF I-90...SUGGESTING CAPPING IN PLACE. IN FACT...THE 08.12Z/09.00Z ECMWF...09.00Z CANADIAN AND GFS ALL POINT TO A DRIER SCENARIO WITH AT MOST SOME MIST/DRIZZLE ON THE NORTH SIDE OF THE FRONT. PREFER THE DRIER SCENARIO AND THUS HAVE DIMINISHED PRECIPITATION CHANCES FOR BOTH THIS AFTERNOON AND TONIGHT. GREATEST CHANCES TONIGHT WOULD BE NORTH OF I-90 WHERE CAPPING IS NOT AS STRONG. PLENTY OF CLOUDS SHOULD EXIST THROUGH TONIGHT THANKS TO ISENTROPIC LIFT OCCURRING. MOS GUIDANCE HAS A GOOD HANDLE ON THIS AND ITS TEMPERATURES SEEM REASONABLE...SO FOLLOWED IT FOR THE FORECAST. TUESDAY AND TUESDAY NIGHT...THE POTENT WAVE EJECTING OUT TONIGHT INTO NORTHEAST WYOMING IS PROGGED TO LIFT UP INTO SOUTHERN MANITOBA TUESDAY NIGHT. AS THIS OCCURS...ALL MODELS ARE IN AGREEMENT IN BRINGING THE SURFACE WARM FRONT INTO AT LEAST THE SOUTHERN PORTIONS OF THE FORECAST AREA. SOUTH OF THIS FRONT ON TUESDAY...THE COMBINATION OF CAPPING AND DECREASING CLOUDS ALONG WITH 850MB TEMPS AROUND 20C SHOULD ALLOW TEMPERATURES TO CLIMB INTO THE LOW TO MID 80S. NORTH OF THE FRONT...LOW CLOUDS AND POTENTIAL FOR SOME PRECIPITATION EXIST...THOUGH THE PRECIPITATION MAY BE TOUGH TO COME BY WITH THE ENTIRE AREA BASICALLY CAPPED. THEREFORE...ONLY 20 PERCENT CHANCES EXIST. ALSO...THE LOW CLOUDS NORTH OF THE FRONT WILL HINDER TEMPERATURES FROM CLIMBING AS MUCH...ESPECIALLY TOWARDS TAYLOR COUNTY WHERE READINGS MAY ONLY GET TO 70. FOR TUESDAY NIGHT...A RENEWED SURGE OF ISENTROPIC LIFT/MOISTURE TRANSPORT IS PROGGED TO OCCUR...FOCUSED FROM NORTHERN MINNESOTA INTO THE NORTHERN HALF OF WISCONSIN PER 09.00Z GFS/NAM AND 09.06Z NAM. KEPT A 30-40 PERCENT CHANCE GOING NORTH OF I-94. FOR THE REST OF THE AREA...CAPPING AND LACK OF FORCING RESULTS IN ONLY A 20 PERCENT CHANCE...AND THAT IS REALLY IN CASE AN MCS FORMS AND TRIES TO DIVE FARTHER SOUTH THAN EXPECTED. WARM NIGHT ON TAP WITH LOWS 5 TO 10 DEGREES BELOW THE NORMAL HIGHS. WEDNESDAY AND WEDNESDAY NIGHT...ATTENTION SHIFTS TO THE SOUTHWEST AS THE REST OF THE WESTERN TROUGH IS PROGGED TO EJECT OUT TOWARDS THE CENTRAL PLAINS. THE 09.00Z GFS IS BY FAR THE FASTEST TO DO SO...BUT AS SEEN THE PAST FEW DAYS...CONTINUES TO SLOW DOWN EACH RUN. THE SLOWER SOLUTIONS OF THE ECMWF AND CANADIAN SEEM MORE REASONABLE... GIVEN STRONG RIDGING DOWNSTREAM. AHEAD OF THIS WESTERN TROUGH...MOST MODELS ARE INDICATING A SUB-TROPICAL SHORTWAVE MOVING THROUGH THE SOUTHWEST FLOW AND CROSSING THE AREA DURING THE AFTERNOON. THIS SHORTWAVE COMING THROUGH DURING TIME OF PEAK HEATING WOULD FAVOR SOME SHOWERS AND THUNDERSTORMS FORMING...THUS MAINTAINED 40-50 PERCENT CHANCES. CHANCES ARE SIMILAR FOR WEDNESDAY NIGHT AS MOISTURE TRANSPORT INCREASES AHEAD OF THE UPPER TROUGH AND WITH THE SUB TROPICAL SHORTWAVE STILL LINGERING IN THE AREA DURING THE EVENING. SPC DAY 3 OUTLOOK MENTIONED A SLIGHT RISK...SINCE THERE WILL BE PLENTY OF INSTABILITY THANKS TO A WARM AND HUMID AIRMASS IN PLACE. HOWEVER...THE 0-6KM SHEAR SHOWN BY BOTH THE GFS AND ECMWF IS ONLY 20 KT. THEREFORE...FOR NOW HAVE DECLINED TO MENTION ANY SEVERE WEATHER POTENTIAL IN THE HWO. .LONG TERM...THURSDAY THROUGH SUNDAY NIGHT FOCUS AS HAS BEEN THE PAST MANY DAYS IS HOW FAST THE REST OF THE WESTERN TROUGH...IN THE FORM OF AN UPPER LOW...PUSHES EASTWARD... WHICH MODELS ARE STILL AT ODDS WITH. HOWEVER...THE SAME TRENDS ARE APPEARING...WITH THE GFS REMAINING TOO PROGRESSIVE WITH THE TROUGH AND YET SLOWING DOWN EACH RUN. THEREFORE...FOLLOWED A SOLUTION CLOSER TOWARDS A CONSENSUS THAT IS BIASED A LITTLE MORE TO THE 09.00Z ECMWF. IN THIS SCENARIO...THE UPPER LOW HEADS EAST-NORTHEAST AT A SLOW PACE...PERHAPS REACHING ILLINOIS SUNDAY MORNING. THE FORECAST AREA EVENTUALLY ENDS UP ON THE NORTH SIDE OF THE UPPER LOW...A FAVORABLE POSITION FOR DEFORMATION PRECIPITATION. FOR THURSDAY AND FRIDAY...HOWEVER...THE AREA IS BASICALLY IN A WARM SECTOR AHEAD OF THE UPPER LOW. AGEOSTROPHIC CURVATURE DIVERGENCE AT 500MB INCREASES WITH THE APPROACH OF THE UPPER LOW...SO PRECIPITATION CHANCES LOOK DECENT THROUGH FRIDAY. TEMPERATURES SHOULD GRADUALLY BE ON THE DECLINE WITH THE APPROACH OF THE UPPER LOW...PERHAPS EVEN TO SLIGHTLY BELOW NORMAL BY THE WEEKEND GIVEN THE AREA IN POTENTIAL DEFORMATION. IT APPEARS BY SUNDAY NIGHT...THE UPPER LOW WILL BE EAST OF THE AREA...ALLOWING FOR DRYING CONDITIONS. && .AVIATION...TODAY AND TONIGHT THE COMPUTER MODELS ARE GENERATING A VARIETY OF SOLUTIONS THIS MORNING WHICH RESULTS IN MUCH UNCERTAINTY FOR THE AVIATION FORECAST. AT 3 AM...THERE IS A LINE OF SHOWERS AND THUNDERSTORMS ACROSS WESTERN MINNESOTA. HOWEVER THE MAIN QUESTION WITH THIS LINE IS IF IT CAN SURVIVE...GIVEN THAT IT WILL BE MOVING EAST INTO A SLIGHTLY DRIER AIR MASS. WITH THE BEST MOISTURE TRANSPORT NORTH OF THE AREA...THIS SHOULD HELP SUSTAIN THE PRECIPITATION IN THESE AREAS. FURTHER SOUTH...IT BECOMES A BIT MORE QUESTIONABLE. CURRENT THOUGHTS IS TO KEEP BOTH THE TAF SITES DRY FOR NOW...AND CONTINUE TO MONITOR THE EASTWARD PROGRESSION OF THE LINE. FOR TONIGHT...A WARM FRONT WILL MOVE SLOWLY NORTHWARD TOWARD THE AREA. IN THIS SCENARIO...THERE IS USUALLY A CONCERN FOR AN LIFR TO MVFR DECK OF CLOUDS. HOWEVER...THE AIR MASS ALOFT IS VERY WARM AND THIS SHOULD LIMIT CONVECTION FROM FIRING...THUS...LIMITING THE PROBABILITIES FOR THESE LOWER CEILINGS. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && SHORT/LONG TERM...AJ AVIATION..........BOYNE
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LA CROSSE WI 130 PM CDT MON MAY 9 2011 WIZ017-029-101200- CLARK-TAYLOR- 130 PM CDT MON MAY 9 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF NORTH CENTRAL WISCONSIN. .DAY ONE...TODAY AND TONIGHT STRONG SUSTAINED AND GUSTY EAST WINDS ARE EXPECTED THIS AFTERNOON ACROSS NORTH CENTRAL WISCONSIN BEHIND A DEPARTING COMPLEX OF RAIN AND THUNDERSTORMS. SUSTAINED WINDS OF UP TO 40 MPH WITH SOME GUSTS UP TO 60 MPH IS EXPECTED. THERE IS A CHANCE OF THUNDERSTORMS THROUGH TONIGHT. LIGHTNING... HEAVY DOWNPOURS AND SMALL HAIL WOULD BE THE MAIN HAZARDS FROM ANY STORMS THAT OCCUR. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY A CHANCE OF THUNDERSTORMS CONTINUES THROUGH FRIDAY...WITH THE GREATEST CHANCES WEDNESDAY THROUGH THURSDAY NIGHT. IT IS TOO EARLY TO DETERMINE IF SEVERE WEATHER WILL OCCUR WITH ANY OF THE STORMS. HOWEVER...THE POTENTIAL WILL EXIST FOR THE STORMS TO PRODUCE HEAVY RAINFALL AS MORE HUMID AIR MOVES INTO THE AREA. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. .EMERGENCY MANAGEMENT COORDINATION... NO WEBINAR IS SCHEDULED. IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ032>034-041>044- 053>055-061-101200- 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- 130 PM CDT MON MAY 9 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF SOUTHEAST MINNESOTA...NORTHEAST IOWA...AND SOUTHWEST INTO CENTRAL WISCONSIN. .DAY ONE...TODAY AND TONIGHT THERE IS A CHANCE OF THUNDERSTORMS THROUGH TONIGHT. LIGHTNING... HEAVY DOWNPOURS AND SMALL HAIL WOULD BE THE MAIN HAZARDS FROM ANY STORMS THAT OCCUR. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY A CHANCE OF THUNDERSTORMS CONTINUES THROUGH FRIDAY...WITH THE GREATEST CHANCES WEDNESDAY THROUGH THURSDAY NIGHT. IT IS TOO EARLY TO DETERMINE IF SEVERE WEATHER WILL OCCUR WITH ANY OF THE STORMS. HOWEVER...THE POTENTIAL WILL EXIST FOR THE STORMS TO PRODUCE HEAVY RAINFALL AS MORE HUMID AIR MOVES INTO THE AREA. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. .EMERGENCY MANAGEMENT COORDINATION... NO WEBINAR IS SCHEDULED. DAS/AJ
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LA CROSSE WI 859 AM CDT MON MAY 9 2011 IAZ009>011-MNZ088-095-096-WIZ017-029-032>034-041-042-053-091500- ALLAMAKEE-BUFFALO-CLARK-FILLMORE-HOUSTON-HOWARD-JACKSON-LA CROSSE-MONROE-TAYLOR-TREMPEALEAU-VERNON-WINNESHIEK-WINONA- 859 AM CDT MON MAY 9 2011 AT 853 AM...DOPPLER RADAR INDICATED A LINE OF STRONG THUNDERSTORMS FROM NEAR EAU CLAIRE AND MONDOVI WISCONSIN...TO PRESTON AND LEROY MINNESOTA...MOVING EAST AT 30 TO 40 MPH. WIND GUSTS OF 35 TO 40 MPH...SMALL HAIL AND HEAVY RAIN MAY ACCOMPANY THIS LINE OF THUNDERSTORMS AS IT MOVES THROUGH. LOCATIONS THAT MAY BE AFFECTED INCLUDE... MEDFORD...ARCADIA...HOLMEN...LA CRESCENT...BLACK RIVER FALLS...CALEDONIA...LA CROSSE...WEST SALEM....AND VIROQUA. LIGHTNING CAN BE A KILLER AND MAY STRIKE MILES AWAY FROM THE STORM. MOVE INDOORS OR FIND A VEHICLE TO SHELTER IN. THESE WIND GUSTS COULD BLOW AROUND OUTDOOR FURNITURE AND OTHER LIGHT OBJECTS. SMALL BRANCHES MAY ALSO FALL. SEEK SAFE SHELTER INSIDE A BUILDING. DAS
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LA CROSSE WI 1029 AM CDT MON MAY 9 2011 IAZ010-011-019-029-030-WIZ029-034-042>044-053>055-061-091630- ADAMS-ALLAMAKEE-CHICKASAW-CLARK-CLAYTON-CRAWFORD-FAYETTE-GRANT- JACKSON-JUNEAU-MONROE-RICHLAND-VERNON-WINNESHIEK- 1029 AM CDT MON MAY 9 2011 AT 1020 AM...DOPPLER RADAR INDICATED A LINE OF STRONG THUNDERSTORMS EXTENDING FROM NEAR BLACK RIVER FALLS...THROUGH SPARTA... VIROQUA...AND WAUKON IOWA...MOVING SOUTHEAST AT 30 MPH. THESE STORMS HAVE A HISTORY OF TORRENTIAL DOWNPOURS WITH RAINFALL WITHIN ONE HOUR OF A HALF OF AN INCH TO AN INCH. WIND GUSTS OF 30 TO 40 MPH MAY ACCOMPANY THESE STRONG THUNDERSTORMS. LOCATIONS THAT MAY BE AFFECTED INCLUDE... TOMAH...MAUSTON...RICHLAND CENTER...BOSCOBEL...AND PLATTEVILLE IN WISCONSIN...AND OELWEIN...ELKADER...AND STRAWBERRY POINT IN NORTHEAST IOWA. FREQUENT LIGHTNING CAN BE A KILLER AND MAY STRIKE MILES AWAY FROM THE STORM. MOVE INDOORS OR FIND A VEHICLE TO SHELTER IN. HEAVY RAIN COULD ALSO LEAD TO MINOR FLOODING OR A SHORT PERIOD OF STANDING WATER. STAY CLEAR OF DRAINAGE AREAS AND AVOID AREAS OF HIGH WATER IF THEY DEVELOP. DAS
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LA CROSSE WI 1142 AM CDT MON MAY 9 2011 MNZ079-WIZ017-029-032>034-092000- WABASHA-TAYLOR-CLARK-BUFFALO-TREMPEALEAU-JACKSON- INCLUDING THE CITIES OF...MEDFORD...NEILLSVILLE... BLACK RIVER FALLS 1142 AM CDT MON MAY 9 2011 ...VERY STRONG WINDS POSSIBLE OVER NEXT FEW HOURS... STRONG EASTERLY WINDS WILL INCREASE BEHIND A CLUSTER OF THUNDERSTORMS CURRENTLY MOVING ACROSS NORTH WESTERN WISCONSIN. SUSTAINED EASTERLY WINDS OF 30 TO 40 MPH WITH SOME GUSTS UP TO 50 MPH WILL BE POSSIBLE ONCE THE THUNDERSTORMS END OVER THE NEXT FEW HOURS. THESE WINDS WILL LAST FOR A HALF HOUR TO AN HOUR AND COULD CAUSE SOME LARGE TREE BRANCHES TO FALL. TRAVEL WILL BECOME DIFFICULT FOR ANY HIGH PROFILE VEHICLES TRAVELING ON NORTH TO SOUTH ROADWAYS. HALBACH
The national radar mosaic for the moment the first event began.
2 high wind. Local standard time, as filed.
Trees were uprooted in Neillsville.
Trees were uprooted falling on power lines along County Road I.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2011Every state in 2011This day in weather historyWarnings in Wisconsin, May 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: 301278, 301280.