The afternoon of September 27th, a strong cold front moved through the Upper Midwest. Several bands of showers and isolated thunderstorms developed along and behind this cold front.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
The afternoon of September 27th, a strong cold front moved through the Upper Midwest. Several bands of showers and isolated thunderstorms developed along and behind this cold front. Due to strong winds just above the surface, several non-thunderstorm wind gusts occurred as showers produced 50 to 60 mph winds. Some of the strong winds blew down trees and large limbs.
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 27, 1:57 PM CST, 1 hour 18 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
257 PM CDT SUN SEP 27 2009
.DISCUSSION...
THE FORECAST CHALLENGES CENTER ON HANDLING THIS TRANSITION TO A
MORE AMPLIFIED UP AND DOWN WEATHER PATTERN...AND THUS WINDS
TONIGHT AND TOMORROW ALONG WITH TEMPS THROUGH THE FIRST FEW DAYS
OF THE FORECAST.
A VIGOROUS UPPER LOW EVOLVING OVER THE UPPER MIDWEST THIS AFTN.
THE GOES WV LOOP AND RUC ANALYSIS OF UPPER LEVEL POTENTIAL
VORTICITY SHOW A NICE SUPPRESSION AND TROP FOLD FEATURE EVOLVING
SOUTHEAST INTO WRN MN THIS AFTN. VAD PROFILERS SHOW A STRONG
UNIDIRECTIONAL FLOW WITH THIS AND 18Z RUC AND SFC OBS UPSTREAM
INDICATE ADVISORY CRITERIA WIND TO LIKELY REMAIN OVER MUCH OF THE
ADVISORY AREA THROUGH THE CURRENT TIME WINDOW OF THE HEADLINE. SO
HAVE MADE NO CHANGES TO THAT. WINDY ACROSS THE REMAINDER OF THE
AREA AS WELL WHICH WILL LAST THROUGH THE NIGHT AS GRADIENT HOLDS
TIGHT YET ISALLOBARIC EFFECT OF PRESSURE RISES ALSO CONTINUES.
ALSO ASSOCIATED WITH THE PV ANOMALY IS A STRONG MID-LEVEL VORT
AND COOL AIR ADVECTION. RADAR MOSAIC SHOWING SCATTERED TO NUMEROUS
SHOWERS FORMING UNDER THE ADVECTION OF THESE PARAMETERS INTO WRN
MN. THESE SHOULD EXPAND EASTWARD OVER CTRL MN AND INTO WRN WI
THROUGH TONIGHT. HAVE ADJUSTED UP POPS FOR THESE. SHOULD BE LIGHT
QPF BUT FAIRLY GOOD COVERAGE IN WRN WI. CLOUDS TO EXPAND ACROSS
MUCH OF THE AREA BY OVERNIGHT WITH THE LOW LEVEL COLD AIR
ADVECTION.
HAVE USED A BLEND OF THE NAM AND GFS SOUNDINGS WITH CURRENT
FORECAST FOR WIND POTENTIAL AND TEMPS ON MON. THE SYNOPTIC SETUP
FAVORS STRONGER WINDS OVER SRN AND ERN MN AS WELL AS WRN WI. WRN
WI AND MUCH OF ERN MN TENDS NOT TO SEE THE HIGHEST WINDS.
HOWEVER...EVEN WITH BROKEN TO OVERCAST CONDITIONS...LAPSE RATES IN
THE LOWEST 2 TO 3 THOUSAND FEET ARE FORECAST TO BE NEAR DRY
ADIABATIC WITH 35 TO 40 KT WINDS WITHIN THAT 2 TO 3 THOUSAND FOOT
LAYER. FORECAST HIGH TEMPS OBVIOUSLY MUCH COOLER THAN TODAY...WITH
DIURNAL CLIMB OF ONLY 6 TO 8 DEGREES...BUT SFC TEMPS STILL ENOUGH
TO CREATE THESE FAVORABLE LAPSE RATES AND BRING DOWN GOOD WINDS.
SO HAVE NEAR WIND ADVISORY CRITERIA FORECAST FOR A GOOD PORTION
OF THE AREA. EVE SHIFT WILL WATCH INCOMING 00Z GUIDANCE AS CURRENT
ADVISORY EXPIRES AND WEIGH IF WE NEED ANOTHER FOR MON LATE MORNING
AND AFTN. EITHER WAY...WINDY AND MUCH COOLER WITH THE FEEL OF
AUTUMN.
HIGH PRESSURE RIDGE TO SLOWLY MOVE OVER THE AREA TUE. THE SFC
WINDS ARE FORECAST TO SLACKEN ENOUGH IN WRN MN MONDAY NIGHT WITH
CLEARING THAT TEMPS SHOULD TAKE A DIVE. THIS MAY HAPPEN IN ENOUGH
TIME FOR SOME FROST. TUE NIGHT THE SCENARIO IS MORE LIKELY FOR
FROST IN OUTLYING PORTIONS OF CTRL AND ERN MN AND WRN WI. HAVE
ADJUSTED GRIDS TOWARDS LOWER MOS AND LOWER 09Z SREF MEMBERS.
MODEL CONSISTENCY REMAINS VERY GOOD WITH REGARD TO THE NEXT
AMPLIFIED SYSTEM IN THE ACTIVE FLOW WHICH IS CENTERED ON THU AND
THU NIGHT. STRONG ELEVATED MOISTURE TRANSPORT ON WED NIGHT STILL
SEEN ON GUIDANCE COMING INTO SW AND WRN MN AND KEEP POP
INTRODUCTION THEN. LIKELY POPS STILL VERY MUCH WARRANTED ON THU
AND EVEN INTO THU NIGHT ACCOUNTING FOR A SLIGHT SLOW DOWN DUE TO A
SUCH AN AMPLIFIED PATTERN AS MENTIONED IN PREV AFD. 12Z GFS CAME
IN A LOT LIKE THE 00Z AND 12Z ECMWF. ONE CONCERN WITH THESE
COMPARED TO OUR FORECAST IS THAT THESE MODELS TRY TO ADVECT DRIER
AIR IN FROM THE EAST AND HOLD MUCH OF THE RAIN IN WRN AND SRN MN.
EITHER WAY THOUGH...CONSISTENCY FOR DAYS HAS BEEN THAT A LIKELY
ONE INCH PLUS RAIN EVENT FOR MUCH OF WEST CENTRAL AND SOUTH
CENTRAL MN.
&&
.AVIATION... /18Z TAF ISSUANCE/
COLD FRONT PUSHING EAST OF KMSP AND KRNH ATTM WITH PASSAGE AT KEAU
AROUND 20Z. BKN-OVC MID LEVEL CLOUDS THIS AFTERNOON IN THE WAKE OF
THE FRONT ALONG WITH INCREASING NW WINDS. BEST PRESSURE RISES
PASSING ACROSS SD/NE WITH NEAR 30 KNOT WINDS TO THE REAR. SPEEDS
WILL BE INCREASE ALONG THE MN RIVER INCLUDING KRWF BY 21Z TO
25 TO 30 KNOTS WITH GUSTS NEAR 40 KNOTS. SURFACE LOW PRESSURE OVER
ONTARIO DEEPENS OVERNIGHT WHILE DROPPING SOUTH ACROSS THE CENTRAL
GREAT LAKES AND THEN HOLDS STEADY ON MONDAY. 20 TO 25 KNOT WINDS
LIKELY TONIGHT AND MONDAY WITH GUSTS ON MONDAY INTO THE LOW 30
KNOT RANGE. GFS/NAM DISAGREE ON THE HEIGHT OF THE LOW CEILINGS BY
EARLY MONDAY WITH THE NAM MVFR AND THE GFS VFR. FOLLOWED THE SREF
PROBABILITIES OF GREATER THAN 70 PERCENT FOR MVFR WHICH YIELDED
KSTC...KRNH AND KEAU CEILINGS IN THE 025 TO 030 RANGE WITH 035
FOOT CEILINGS FOR KAXN AND KMSP.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WIND ADVISORY UNTIL 9 PM CDT THIS EVENING FOR BLUE EARTH-BROWN-
CHIPPEWA-FARIBAULT-FREEBORN-LAC QUI PARLE-MARTIN-NICOLLET-
REDWOOD-RENVILLE-SIBLEY-STEELE-WASECA-WATONWAN-YELLOW
MEDICINE.
WI...NONE.
&&
MTF/RAHHAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 112 PM CDT SUN SEP 27 2009 MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028- 281815- 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- 112 PM CDT SUN SEP 27 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND SOUTHERN MINNESOTA...AND WEST CENTRAL WISCONSIN. .DAY ONE...THIS AFTERNOON AND TONIGHT STRONG NORTHWEST WINDS WILL SPREAD ACROSS THE OUTLOOK AREA THIS AFTERNOON AND CONTINUE TONIGHT. THE STRONGEST SUSTAINED WINDS...WITH SPEEDS NEAR 30 MPH ALONG WITH GUSTS OVER 40 MPH... WILL OCCUR OVER WEST CENTRAL INTO SOUTHERN MINNESOTA. A FEW THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON ACROSS WEST CENTRAL WISCONSIN AND SOUTH CENTRAL MINNESOTA. THE STORMS ARE NOT EXPECTED TO BE SEVERE. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NORTHWEST WINDS AT 25 TO 30 MPH WILL OCCUR ACROSS THE OUTLOOK AREA ON MONDAY. A DEVELOPING LOW PRESSURE SYSTEM IS ANTICIPATED TO MOVE INTO THE CENTRAL PLAINS LATE THIS WEEK...AND IT SHOULD BRING A CHANCE OF THUNDERSTORMS...BEGINNING WEDNESDAY NIGHT AND CONTINUING THROUGH THE DAY ON FRIDAY. .SPOTTER INFORMATION STATEMENT... SKYWARN SPOTTER ACTIVATION WILL NOT BE NEEDED. RAH
The national radar mosaic for the moment the first event began.
3 strong wind, 1 high wind. Local standard time, as filed.
A trained spotter measured a 52 mph wind gust near St. Francis which caused several small branches to be blown down.
A trained spotter reported that strong winds blew down an eight inch diameter tree branch in Columbia Heights.
The public reported several small trees blown down in Oakdale.
KBDH or Willmar Airport measured a 66 mph wind gust.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2009Every state in 2009This day in weather historyWarnings in Minnesota, September 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: 190937, 190938, 190940, 190941.