A small complex of thunderstorms became severe across the Twin Cities Metro area, and moved east across portions of west-central Wisconsin during the early morning hours of Tuesday, September 21st. Several reports of severe hail fell in the southern and eastern portions of the Twin Cities, including the Minneapolis/St.
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 MPX wrote it up.
A small complex of thunderstorms became severe across the Twin Cities Metro area, and moved east across portions of west-central Wisconsin during the early morning hours of Tuesday, September 21st. Several reports of severe hail fell in the southern and eastern portions of the Twin Cities, including the Minneapolis/St. Paul International Airport.
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 Twin Cities, MN wrote its last area forecast discussion before the first event at Sep 20, 10:15 PM CST, 2 hours 4 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED FOR 06Z TAFS NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1115 PM CDT MON SEP 20 2010 .MESO UPDATE...ISSUED 816 PM CDT THERE REMAINS POTENTIAL...ALBEIT DECREASING...FOR A COUPLE STRONG TO SEVERE THUNDERSTORMS DURING THE REMAINDER OF TONIGHT ACROSS THE FORECAST AREA. THE PRIMARY UPPER LEVEL LOW IS SEEN ON WATER VAPOR TWISTING EAST INTO SOUTHERN MANITOBA. ANOTHER WAVE IS LIFTING NORTHEAST IN THE MOIST FLOW AHEAD OF THIS FROM CO INTO SOUTHERN SD. A STRONG MID-LEVEL COLD FRONT EXISTS BETWEEN THE TWO AND IS PUSHING EAST AND WILL REPRESENT THE MAIN REASON FOR AT LEAST SHOWERS TO DEVELOP ALONG THE LOW-LEVEL BOUNDARY DUE TO WEAKENING A STRONG CAP. THE SURFACE LOW/TRIPLE POINT IN WESTERN MN WILL CONTINUE TO TRANSLATE NORTHEAST WITH THE WARM FRONTAL BOUNDARY TO ITS EAST SLOWLY LIFTING NORTH...AND THE COLD FRONT EXTENDING SOUTH WRAPPING EASTWARD. THE LOW AND DEEP LAYER SHEAR AND HELICITY VALUES TO THE EAST OF THE BOUNDARY REMAIN VERY HIGH AS SEEN ON THE 00Z MPX RAOB. BUT THE MLCIN VALUES ALSO REMAIN QUITE HIGH...WHICH IS CURRENTLY REFRAINING THE 1000 TO 2000 J/KG OF MUCAPE. IT WOULD SEEM IT WOULD TAKE CONGEALED AND SOMEWHAT SUSTAINED AND QUICK- MOVING ACTIVITY NEAR THE FRONT TO REALLY PRESENT A TORNADO AND POSSIBLY EVEN A WIND THREAT...GIVEN THE STRENGTH OF THE INVERSION AHEAD OF THE FRONT. THE MID-LEVEL LAPSE RATES WILL CONTINUE TO STEEPEN LOOKING AT THE KABR RAOB...AND AS THE MOIST PLUME AND WAVE FROM THE SOUTHWEST INTERSECT THAT...DEVELOPING AND EXISTING STORMS WILL BE ABLE TO UTILIZE THAT ELEVATED INSTABILITY WITH POSSIBLY SOME HAIL. THE HRRR HAS GRADUALLY TRENDED DOWN WITH ITS HIGHER REFLECTIVITY...BUT STILL PROMOTES GOOD COVERAGE OF SHOWERS BY EASTERN MN INTO WESTERN WI OVERNIGHT. THE PRIMARY TIME FOR A STRONG TO SEVERE STORM REMAINS BETWEEN 10 PM AND 3 AM. && .DISCUSSION.../ISSUED 340 PM/ SHORT TERM CONCERN REMAINS CONVECTIVE POTENTIAL ACROSS THE AREA. LATEST SPC MESOSCALE ANALYSIS INDICATES RAPID DESTABILIZATION ACROSS THE REGION AS SFC WMFNT LIFTS ACROSS CENTRAL MN. MIXED LAYER CAPE RISING TO 1000 J/KG OVER SC MN WITH MAIN STRONG LOW LEVEL FLOW(ABOUT 50 KTS AT H85) INTO SW MN ATTM. MID LEVEL WARMING SIGNIFICANT HOWEVER...WITH CAP ESTABLISHED ACROSS WESTERN MN WITH H7 TEMPS OF PLUS 12C ALL THE WAY INTO THE NW CORNER OF THE STATE. WATER VAPOR IMAGERY SHOWING MUCH OF THE TROUGH ENERGY LIFTING INTO WESTERN DAKOTAS NOW. THAT EXTENDS SOUTH INTO COLORADO/NEBRASKA REGION WITH SOME ACCAS INCREASING OVER CENTRAL SOUTH DAKOTA. SHOULD SEE CAP HOLD UNTIL AFTER 00Z OVER WESTERN MN...AS TROUGH SFC FRONT MOVES INTO THAT REGION. TREND OF THE HRRR SHOWS THIS FAIRLY WELL...DEVELOPING ABOUT THAT TIME AND MOVING INTO CENTRAL MN THROUGH 06Z. WILL CONTINUE CHANCE POPS FOR THIS ACTIVITY INCREASING TO LIKELY AFTER 06Z. THIS WILL CONTINUE TO MOVE EAST AS SFC FNT DROPS TO THE SOUTHEAST OF THE AREA THROUGH 18Z TUE. CHANCE POPS REMAIN IN ORDER FOR THE MORNING OVER THE SOUTHEAST CWA FOR THIS. SEVERE POTENTIAL THERE AS WELL INTO THE NIGHT AS ACTIVITY DEVELOPS ALONG THE FNT. SUPERCELL MERING/DEVELOPING INTO LINEAR COMPLEX POSSIBLE. MAIN THREAT WIND AND HAIL AS LAPSE RATES ARE STEEP. HOWEVER...SMALL TORNADO THREAT EARLY IN STORM INITIATION AS WEAK SFC LOW LIFTS INTO NORTHERN CWA...AND ALONG WMFNT. DRIER AIR WORKS INTO THE REGION FOR TUESDAY AFTERNOON...AND INTO WEDNESDAY...AS SFC FRONT DROPS SOUTH AND STALL OVER IOWA. NEXT WESTERN TROUGH LIFTS NORTHEAST AND DEVELOPS SIG SFC LOW OVER SOUTH DAKOTA. THIS LIFTS NORTHEAST ACROSS CENTRAL MN WED NIGHT INTO THU NIGHT. HEAVY RAINFALL REMAINS A DISTINCT POSSIBILITY AS THIS SYSTEM LIFTS OUT SIGNIFICANT CERTAINLY POSSIBLE...WITH PWATS AROUND 2 INCHES...WHICH IS SOME 250% ABOVE NORMAL. MODELS TRENDING BAND OF HEAVY RAINFALL...ALONG AND NORTH OF THE TRACK OF THE SFC LOW....WHICH TRAVEL MAINLY ACROSS CENTRAL CWA. CERTAINLY SOME 2-3 INCH TOTALS POSSIBLE AS SYSTEM LIFTS NORTHEAST. SHOULD SEE IMPROVING CONDITIONS INTO FRIDAY AS SYSTEM EXITS TO THE EAST. LONGER TERM IS A BIT MORE PROBLEMATIC AS GFS AND ECMWF ARE AT ODDS AS TO WHETHER ANOTHER TROUGH FOLLOWS THURSDAYS STORM INTO THE WEEKEND. HAVE TRENDED MORE TOWARD HPC/GFS/GFS ENSEMBLE MEAN FOR THIS PERIOD...WHICH HAS THE MAIN BELT OF THE WESTERLIES ALONG SOUTHERN CANADA...LIMITING SIGNIFICANT COOL AIR PENETRATION SOUTH INTO THE AREA. THIS LEAVES THE AREA IN RATHER HIGH HEIGHTS FOR THIS TIME OF YEARS...WITH TEMPERATURES TRENDING A BIT ABOVE NORMAL INTO NEXT MONDAY. && .AVIATION.../06Z TAF ISSUANCE/ CONVECTION BCMG MR WDSPRD LAST HR OR SO IN E SODAK INTO SW/CNTL MN AS SHRTWV LIFTING OUT OF CO ADDING SM ADDITIONAL FORCING. EXPCT THAT SHWRS AND TSTMS WL CONT TO BCM MR WDSPD ACRS ALL TAF SITES BUT AXN NEXT SVRL HRS. CDFNT NR BRD TO NR RWF MVG E FAIRLY RPDLY WITH 3MB 3HRLY PRES RISES IN ITS WAKE. AS CDFNT PASSES PSTFNTAL PCPN AT RWF/STC/MSP/RNH/EAU MAY CAUSE MFR CIGS/VSBYS OVRNITE. FNT SHUD REACH MSP BY 10Z. KMSP...CDFNT NR RWF SHUD REACH MSP ARND 10Z. MAINLY PSTFNL SHWRS/TSTMS SPRDG NE ACRS SW INTO CNTL MN. PCPN SHUD SPREAD INTO MSP AREA BY 07Z. XPCT MVFR CIGS TO DVLP IN PCPN IN WAKE OF CDFNT. IMPRVG CONDS TO VFR ARND 14Z. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && BAP/DWE
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 804 PM CDT MON SEP 20 2010 MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028- 211200- DOUGLAS-TODD-MORRISON-MILLE LACS-KANABEC-STEVENS-POPE-STEARNS- BENTON-SHERBURNE-ISANTI-CHISAGO-LAC QUI PARLE-SWIFT-CHIPPEWA- KANDIYOHI-MEEKER-WRIGHT-HENNEPIN-ANOKA-RAMSEY-WASHINGTON- YELLOW MEDICINE-RENVILLE-MCLEOD-SIBLEY-CARVER-SCOTT-DAKOTA- REDWOOD-BROWN-NICOLLET-LE SUEUR-RICE-GOODHUE-WATONWAN-BLUE EARTH- WASECA-STEELE-MARTIN-FARIBAULT-FREEBORN-POLK-BARRON-RUSK- ST. CROIX-PIERCE-DUNN-PEPIN-EAU CLAIRE- 804 PM CDT MON SEP 20 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND SOUTHERN MINNESOTA...AND WEST CENTRAL WISCONSIN. .DAY ONE...TONIGHT THERE IS A SMALL RISK OF SEVERE THUNDERSTORMS ACROSS THE OUTLOOK AREA...PRIMARILY IN CENTRAL MINNESOTA AND FAR WESTERN WISCONSIN. A COLD FRONT WILL MOVE EAST ACROSS THE OUTLOOK AREA THROUGH THE NIGHT. SCATTERED THUNDERSTORMS WILL OCCUR ALONG AND AHEAD OF THE FRONT AND GRADUALLY TRAVERSE EAST. A FEW OF THESE STORMS MAY BE CAPABLE OF PRODUCING DAMAGING WINDS AND HAIL UP TO HALF DOLLAR SIZE. THE THREAT OF A TORNADO IS RELATIVELY SMALL AND MAINLY CONFINED TO CENTRAL AND EAST CENTRAL MINNESOTA. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THUNDERSTORMS WILL RETURN OVER THE OUTLOOK AREA WEDNESDAY NIGHT INTO THURSDAY NIGHT AS A STRONG AREA OF LOW PRESSURE MOVES OVER THE REGION. THE PRIMARY THREAT DURING THIS PERIOD WILL BE HEAVY RAIN. RECENT RUNOFF FROM THE PAST RAIN EVENT...HAS CAUSED SEVERAL RIVERS AND STREAMS TO REACH NEAR BANKFULL. ANY ADDITIONAL RAINFALL WILL AGGRAVATE THE FLOOD THREAT...ESPECIALLY FOR TRIBUTARIES ON AND ALONG THE MINNESOTA RIVER IN SOUTHWEST AND SOUTH CENTRAL MINNESOTA. PEOPLE WITH INTERESTS ALONG THE SWOLLEN MINNESOTA RIVER AND ITS ADJACENT TRIBUTARIES SHOULD CONTINUE TO MONITOR THE LATEST STATEMENTS AND FORECASTS. .SPOTTER INFORMATION STATEMENT... SKYWARN SPOTTER ACTIVATION REMAINS POSSIBLE TONIGHT ACROSS THE OUTLOOK AREA...PRIMARILY IN CENTRAL AND EASTERN MINNESOTA AND FAR WESTERN WISCONSIN.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1237 AM CDT TUE SEP 21 2010
MNZ067-074-075-210600-
BROWN-NICOLLET-SIBLEY-
1237 AM CDT TUE SEP 21 2010
...THUNDERSTORMS DEVELOPING OVER BROWN...NICOLLET AND SIBLEY
COUNTIES THROUGH 100 AM CDT...
AT 1235 AM CDT...WEATHER SERVICE RADAR WAS TRACKING A STRONG
THUNDERSTORM 3 MILES WEST OF NEW ULM...OR 7 MILES SOUTHWEST OF
KLOSSNER. THIS STORM WAS MOVING NORTHEAST AT 55 MPH.
HAIL UP TO NICKEL SIZE IS EXPECTED WITH THIS STORM.
* LOCATIONS IN OR NEAR THE PATH OF THIS STORM INCLUDE...
KLOSSNER.
LAFAYETTE.
NEW SWEDEN.
GAYLORD.
LAT...LON 4432 9468 4472 9412 4472 9402 4461 9388
4460 9389 4459 9390 4459 9389 4457 9390
4419 9451
TIME...MOT...LOC 0537Z 227DEG 50KT 4432 9450The Minneapolis radar (KMPX), 37 km away, was scanning. The volume nearest the first event began at 06:17 UTC.
4 hail, 2 thunderstorm wind. Local standard time, as filed.
A few large tree branches were blown down in Rosemount, Minnesota.
Several reports of large hail, up to half dollar size, occurred from Bloomington, to the east side of the International Airport. In addition, the weather observer at the KMSP Airport reported quarter size hail at 12:37 AM CST.
Several large 12-inch diameter tree limbs were blown down around the Highland Park Area of St. Paul, Minnesota, and areas to the northeast.
Several reports of large hail, up to the size of half dollars, occurred from the Highland Park area of St. Paul, northeast across the north side of the city.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2010Every state in 2010This day in weather historyWarnings in Minnesota, September 2010
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: 252045, 252037, 252047, 277904, 252041, 252042.