

293 

WWUS20 KWNS 180001

SEL9

SPC WW 180001

IAZ000-MNZ000-180600-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 449

NWS STORM PREDICTION CENTER NORMAN OK

700 PM CDT WED JUN 17 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTH CENTRAL AND NORTHEAST IOWA

       SOUTH CENTRAL AND SOUTHEAST MINNESOTA



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 700 PM

UNTIL 100 AM CDT.



TORNADOES...HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 15 MILES WEST SOUTHWEST OF

FAIRMONT MINNESOTA TO 25 MILES SOUTH OF LA CROSSE WISCONSIN.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU9).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS.



OTHER WATCH INFORMATION...CONTINUE...WW 439...WW 440...WW

441...WW 442...WW 443...WW 445...WW 444...WW 446...WW 447...WW

448...



DISCUSSION...A VERY UNSTABLE ENVIRONMENT IS PRESENT ACROSS S/SE MN

INTO NRN IA...ALONG AND S OF A SURFACE WARM FRONT AND WEAK SURFACE

WAVE IN SRN MN.  BOUNDARY LAYER DEWPOINTS IN THE 70S AND

TEMPERATURES IN THE 80S ARE CONTRIBUTING TO MLCAPE VALUES OF

3000-4000 J/KG...AND EFFECTIVE BULK SHEAR OVER THIS AREA IS AOA 50

KTS.  THE ENVIRONMENT STRONGLY FAVORS DISCRETE SUPERCELL

DEVELOPMENT...WHILE THE RICH LOW-LEVEL MOISTURE AND 0-1 KM SRH AOA

200 M2/S2 WILL FAVOR TORNADIC SUPERCELLS.  GIVEN THESE ENVIRONMENTAL

CONDITIONS...AN ISOLATED STRONG TORNADO MAY OCCUR.  OTHERWISE...VERY

LARGE HAIL AND ISOLATED DAMAGING WINDS WILL BE POSSIBLE.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 29025.





...THOMPSON

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