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WWUS20 KWNS 202242

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SPC WW 202242

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 674

NWS STORM PREDICTION CENTER NORMAN OK

535 PM CDT THU SEP 20 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MINNESOTA

       WESTERN AND CENTRAL WISCONSIN



EFFECTIVE THIS THURSDAY AFTERNOON AND FRIDAY MORNING FROM 535 PM

UNTIL 100 AM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 60

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 65 MILES WEST

NORTHWEST OF EAU CLAIRE WISCONSIN TO 65 MILES EAST OF EAU CLAIRE

WISCONSIN.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR 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. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...CONTINUE...WW 673...



DISCUSSION...SLIGHTLY ELEVATED MCS WITH EMBEDDED SUPERCELLS NOW IN

THE TWIN CITIES AREA EXPECTED TO CONTINUE GENERALLY E INTO WI

THROUGH MID EVENING.  ADDITIONAL DEVELOPMENT MAY CONTINUE TO OCCUR

ON SSW FLANK OF SYSTEM...I.E. IN DIRECTIONAL OF 40+ KT LLJ.

RECOVERING AIR MASS ALONG AND N OF WARM FRONT EXTENDING ESE INTO

CNTRL WI SHOULD ALLOW SVR THREAT TO PERSIST DESPITE FACT THAT

CONVECTIVE SYSTEM WILL BECOME FARTHER REMOVED FROM GREATEST ELEVATED

THETA-E INFLOW.  WHILE A TORNADO CANNOT BE RULED OUT...MAIN THREATS

SHOULD BE WIND/HAIL GIVEN CURRENT AND EXPECTED STORM MODE...AND LESS

FAVORABLE SFC WARM SECTOR AIR MASS WITH EWD EXTENT.

FARTHER N...OTHER MORE ELEVATED STORMS EXPECTED TO CONTINUE E ACROSS

NW WI.  THESE SHOULD WEAKEN AS THEY BECOME FURTHER ELEVATED AND

INCREASINGLY REMOVED FROM ELEVATED MOIST INFLOW.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 27035.





...CORFIDI

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