A cluster of slow moving thunderstorms produced very heavy rain in the late evening hours of August 13th and the early morning hours of August 14th. This caused flooding of roadways and mudslides in northern Trempealeau and northern Buffalo Counties.
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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.
A cluster of slow moving thunderstorms produced very heavy rain in the late evening hours of August 13th and the early morning hours of August 14th. This caused flooding of roadways and mudslides in northern Trempealeau and northern Buffalo Counties.
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 Aug 13, 1:48 PM CST, 10 hours 37 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 248 PM CDT THU AUG 13 2009 .SHORT TERM...THROUGH SATURDAY NIGHT MAIN FORECAST CONCERN IS WITH THE RAIN CHANCES THROUGH THE PERIOD. SURFACE ANALYSIS THIS AFTERNOON SHOWS HIGH PRESSURE OVER LOWER MICHIGAN. A WEAK AREA OF LOW PRESSURE WAS OVER SOUTHEAST MONTANA WITH A WARM FRONT ACROSS NORTH DAKOTA AND NORTHERN MINNESOTA. LOCAL AND REGIONAL RADARS THIS AFTERNOON SHOWING SCATTERED THUNDERSTORMS FROM WESTERN WISCONSIN AND SOUTHERN MINNESOTA INTO NORTHERN IOWA. THESE ARE IN RESPONSE TO A MCV THAT VISIBLE SATELLITE SHOWS IS SPINNING OVER SOUTH CENTRAL MINNESOTA. ML CAPES BETWEEN 2000 AND 2500 J/KG AHEAD OF THE MCV AND PROFILERS STILL SHOW A DECENT SOUTHWEST FLOW INTO THE THE STORMS WITH SLATER SHOWING ABOUT 25 KNOTS AT 850 MB. DECENT SPEED CONVERGENCE IN THIS FLOW WITH BLUE RIVER ONLY SHOWING ABOUT 10 KNOTS AT 850 MB. EXPECT THIS ACTIVITY WILL CONTINUE WELL INTO THE EVENING AS THE MCV WORKS EAST INTO WISCONSIN AND HAVE GONE WITH SCATTERED SHOWERS AND THUNDERSTORMS FOR MUCH OF THE EVENING. GIVEN THE SLOW MOVEMENT OF THE MCV...IT COULD STILL BE CLOSE ENOUGH TO PRODUCE SOME LIFT WELL INTO FRIDAY. THE NOSE OF THE LOW LEVEL JET AND MOISTURE TRANSPORT WILL SHIFT EAST OF THE AREA AFTER 06Z TONIGHT...HOWEVER...THE REGION WILL REMAIN IN THE CONVERGENT EASTERN GRADIENT WELL INTO FRIDAY. WITH THE CONTINUED WARM AIR ADVECTION...THE 13.12Z NAM SHOWS UP TO 4 MICROBARS/S OF UP GLIDE ON THE 310K ISENTROPIC SURFACE THROUGH TONIGHT BEFORE MOVING NORTHEAST OF THE AREA FRIDAY. WITH THESE FEATURES WILL CONTINUE WITH THE LOW RAIN CHANCES AFTER 06Z TONIGHT THROUGH FRIDAY. THE LOW LEVEL JET WILL LIFT WELL NORTH OF THE FRIDAY NIGHT AND SATURDAY PROVIDING FOR A COUPLE OF DRY PERIODS. THE MEAN LONG WAVE TROUGH WILL THEN START TO MOVE ACROSS THE ROCKIES WITH SHORT WAVE TROUGHS COMING OUT AHEAD OF THE MAIN TROUGH. THE FIRST OF THESE SHORT WAVE TROUGHS IS EXPECTED TO MOVE ACROSS THE UPPER MIDWEST SATURDAY NIGHT. THE COLD FRONT IS EXPECTED TO BE WELL TO THE WEST OF THE AREA ACROSS WESTERN MINNESOTA INTO CENTRAL KANSAS. WITH THE WARM AIR ADVECTION AHEAD OF THE COLD FRONT...THE NAM IS ONCE AGAIN SHOWING UP TO 4 MICROBARS/S OF UP GLIDE ON THE 305K SURFACE SPREADING ACROSS THE AREA. MAINTAINED THE RAIN CHANCES ACROSS THE WESTERN SECTIONS SATURDAY EVENING AND THEN SPREAD THEM EAST ACROSS THE REST OF THE AREA HEADING INTO SUNDAY MORNING. .LONG TERM...SUNDAY THROUGH THURSDAY THE LATEST SET OF MEDIUM RANGE MODELS REMAIN CONSISTENT WITH THE OVERALL SYNOPTIC PATTERN. THE LONG WAVE TROUGH IS STILL EXPECTED TO MOVE INTO THE CENTRAL PART OF THE COUNTRY EARLY IN THE PERIOD AND THEN LINGER OVER THE REGION THROUGH THE REMAINDER OF THE PERIOD. IN FACT...THE TROUGH MAY BEGIN TO AMPLIFY TOWARD THE END OF NEXT WEEK AS A STRONG SHORT WAVE TROUGH AND UPPER LEVEL LOW TOP THE WESTERN CONUS RIDGE AND DROP INTO THE TROUGH. AT THE SURFACE...THE MODELS ARE NOT IN SUCH GOOD AGREEMENT. THE 13.06Z GFS IS VERY PROGRESSIVE WITH THE COLD FRONT COMPARED WITH THE 13.00Z ECMWF AND GFS ENSEMBLES. GIVEN THE STRENGTH OF THE DOWNSTREAM SUBTROPICAL RIDGE OVER THE SOUTHEASTERN PART OF THE COUNTY...BELIEVE THE GFS IS TOO AGGRESSIVE WITH THE FRONT AND HAVE STAYED WITH THE SLOWER SOLUTIONS. THIS ESSENTIALLY MEANS THE FRONT WILL BE OVER THE AREA OR VERY NEAR TO IT THROUGH THE ENTIRE PERIOD. AT THIS POINT...UNABLE TO PICK OUT ANY PERIOD THAT COULD POTENTIALLY BE DRY SO HAVE INCLUDED RAIN CHANCES THROUGH THE ENTIRE PERIOD. DID LOWER TEMPERATURES SOME THROUGH THE PERIOD GIVEN THE EXPECTED CLOUD COVER AND POTENTIAL FOR RAIN. && .AVIATION... AN UPPER LEVEL CIRCULATION WILL SPIN ACROSS THE AREA THIS AFTERNOON/EVENING...TAPPING INTO INSTABILITY...A MOISTURE FEED...AND A WARM FRONT TO SPARK SCT SHRA/TS. THERE WILL BE SOME IMPACT TO KRST/KLSE THROUGH ABOUT 02Z OR SO...AND WILL COVER THIS WITH CB/VCTS...ALONG WITH SOME SHORT TEMPO TS GROUPS. MIXING SHOULD CONTINUE THE GUSTY CONDITIONS UNTIL A COUPLE HOURS AFTER SUNDOWN. THE WARM FRONT WILL LIKELY CREEP NORTH ON FRIDAY...BUT A PERSIST MOISTURE FEED INTO THE BOUNDARY...ALONG WITH THE INFLUENCE OF THE LOW LEVEL JET...COULD LEAD TO MORE CONVECTION IN THE VICINITY OF THE BOUNDARY. BELIEVE THIS WILL BE NORTH OF KLSE/KRST AT THIS TIME. STRONGER LOW LEVEL WINDS/MIXING WILL RESULT IN ANOTHER GUSTY DAY. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && SHORT/LONG TERM...04 AVIATION...RIECK
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LA CROSSE WI 456 AM CDT THU AUG 13 2009 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-032>034- 041>044-053>055-061-141000- ADAMS-ALLAMAKEE-BUFFALO-CHICKASAW-CLARK-CLAYTON-CRAWFORD-DODGE- FAYETTE-FILLMORE-FLOYD-GRANT-HOUSTON-HOWARD-JACKSON-JUNEAU-LA CROSSE- MITCHELL-MONROE-MOWER-OLMSTED-RICHLAND-TAYLOR-TREMPEALEAU-VERNON- WABASHA-WINNESHIEK-WINONA- 456 AM CDT THU AUG 13 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF SOUTHEAST MINNESOTA... NORTHEAST IOWA AND SOUTHWEST INTO CENTRAL WISCONSIN. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS WILL BE POSSIBLE THROUGHOUT THE DAY...AND LINGERING INTO THE NIGHT AS A WARM AND MOIST AIRMASS CONTINUES TO STREAM INTO THE REGION ALONG WITH A WEAK WEATHER SYSTEM ALOFT. WHILE ORGANIZED SEVERE STORMS ARE NOT EXPECTED...A FEW STRONGER STORMS WITH BRIEF HAIL OR AN ISOLATED STRONG WIND GUST ARE POSSIBLE ESPECIALLY FROM MID AFTERNOON INTO LATE EVENING. PROBABLY THE GREATER THREAT WILL BE CLOUD TO GROUND LIGHTNING...AND TORRENTIAL RAINFALL RATES WITH THE SLOW MOVING STORMS THAT COULD PRODUCE SOME SHORT TERM RUNOFF ISSUES OVER URBAN AREAS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THERE WILL BE A CONTINUED THREAT OF A FEW THUNDERSTORMS INTO FRIDAY. SEVERE STORMS ARE NOT EXPECTED. AN UNSETTLED...WARM AND HUMID PERIOD WILL BE IN PLACE FROM SATURDAY NIGHT INTO EARLY NEXT WEEK AS A WEAK COLD FRONT MOVES VERY SLOWLY THROUGH THE AREA. IT REMAINS TOO EARLY TO DISCERN THE SEVERE WEATHER POTENTIAL THROUGH THIS PERIOD...THOUGH IT DOES APPEAR THAT AMPLE MOISTURE AND A SLOW FRONTAL MOVEMENT MAY LEAD TO THE POSSIBILITY OF HEAVY RAIN WITH MULTIPLE WAVES OF THUNDERSTORMS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH SATURDAY...BUT A FEW STRONGER STORMS TODAY MAY NEED TO BE WATCHED ON A LOCALIZED BASIS. WIDESPREAD OR ORGANIZED DEPLOYMENT IS NOT EXPECTED. .EMERGENCY MANAGEMENT COORDINATION... NO CALL IS SCHEDULED. BINAU
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LA CROSSE WI 945 PM CDT THU AUG 13 2009 WIZ032-140345- BUFFALO- 945 PM CDT THU AUG 13 2009 ...STRONG THUNDERSTORMS AFFECTING NORTHERN BUFFALO COUNTY... AT 939 PM...DOPPLER RADAR INDICATED STRONG THUNDERSTORMS WITH DANGEROUS LIGHTNING AND HEAVY RAINFALL ADVANCING TOWARD NORTHERN PARTS OF BUFFALO COUNTY...MOVING EAST AT 25 MPH. THESE STORMS COULD ALSO PRODUCE HAIL UP TO THE SIZE OF DIMES...ALONG WITH WIND GUSTS OF 40 TO 50 MPH. HEAVY RAIN COULD 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. DANGEROUS LIGHTNING CAN STRIKE MILES FROM A STORM...SO GO INDOORS IF A STORM AFFECTS YOUR LOCATION. THOMPSON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LA CROSSE WI 1059 PM CDT THU AUG 13 2009 WIZ033-140500- TREMPEALEAU- 1059 PM CDT THU AUG 13 2009 AT 1055 PM...DOPPLER RADAR INDICATED STRONG THUNDERSTORMS FROM ELEVA TO 19 MILES WEST OF WICKHAM VALLEY...MOVING EAST AT 25 MPH. TORRENTIAL DOWNPOURS AND FREQUENT DANGEROUS LIGHTNING WILL ACCOMPANY THESE STRONG THUNDERSTORMS. LOCATIONS THAT MAY BE AFFECTED INCLUDE... STRUM...THE BORST VALLEY AREA...CHIMNEY ROCK...WALEK KNOB AND OSSEO. 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 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. DTJ
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE LA CROSSE WI 1148 PM CDT THU AUG 13 2009 WIZ017-029-034-140645- CLARK-JACKSON-TAYLOR- 1148 PM CDT THU AUG 13 2009 ...STRONG THUNDERSTORMS AFFECTING CLARK...JACKSON AND TAYLOR COUNTIES... AT 1146 PM...DOPPLER RADAR INDICATED STRONG THUNDERSTORMS WITH HEAVY RAINFALL AND DANGEROUS LIGHTNING ADVANCING INTO WESTERN SECTIONS OF CLARK...JACKSON AND TAYLOR...MOVING EAST AT 25 MPH. 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 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. THOMPSON
SPECIAL WEATHER STATEMENT...CORRECTION NATIONAL WEATHER SERVICE LA CROSSE WI 1149 PM CDT THU AUG 13 2009 WIZ017-029-034-140645- CLARK-JACKSON-TAYLOR- 1149 PM CDT THU AUG 13 2009 ...STRONG THUNDERSTORMS AFFECTING CLARK...JACKSON AND TAYLOR COUNTIES... AT 1146 PM...DOPPLER RADAR INDICATED STRONG THUNDERSTORMS WITH HEAVY RAINFALL AND DANGEROUS LIGHTNING ADVANCING INTO WESTERN SECTIONS OF CLARK...JACKSON AND TAYLOR COUNTIES...MOVING EAST AT 25 MPH. 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 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. THOMPSON
The La Crosse radar (KARX), 97 km away, was scanning. The volume nearest the first event began at 06:26 UTC.
2 flash flood. Local standard time, as filed.
Law Enforcement reported numerous mudslides in the northeast portions of Buffalo County and flooding of streets in the city of Mondovi.
Law Enforcement reported water over several side roads in the town of Eleva and water over several county roads in northern Trempealeau 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, August 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: 184657, 184667.