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WWUS20 KWNS 020611

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 641

NWS STORM PREDICTION CENTER NORMAN OK

115 AM CDT THU SEP 2 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       SOUTHWEST MINNESOTA

       NORTHEAST NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS THURSDAY MORNING FROM 115 AM UNTIL 900 AM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 60

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 95

STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES NORTH

NORTHWEST OF WORTHINGTON MINNESOTA TO 40 MILES WEST SOUTHWEST OF

NORFOLK NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 640...



DISCUSSION...TSTMS EXPECTED TO CONTINUE FORMING IN MOIST AXIS

DOWNSTREAM FROM ZONE OF ASCENT ASSOCIATED WITH AMPLIFYING SHORTWAVE

TROUGH OVER THE DAKOTAS.  COMBINATION OF MID LVL COOLING...FAIRLY

RICH LOW LVL MOISTURE...AND 40+ KT WLY MID LVL FLOW MAY SUPPORT A

FEW SUSTAINED STORMS/SUPERCELLS WITH A THREAT FOR HAIL AND POSSIBLY

LOCALLY DMGG WIND.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 50

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM

MOTION VECTOR 27030.





...CORFIDI

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