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000 

WWUS20 KWNS 210732

SEL1

SPC WW 210732

MNZ000-NDZ000-SDZ000-211500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 431

NWS STORM PREDICTION CENTER NORMAN OK

230 AM CDT THU JUN 21 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       FAR WESTERN MINNESOTA

       SOUTHERN NORTH DAKOTA

       NORTHERN SOUTH DAKOTA



EFFECTIVE THIS THURSDAY MORNING FROM 230 AM UNTIL 1000 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 55

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 55 MILES NORTH

NORTHWEST OF BUFFALO SOUTH DAKOTA TO 50 MILES NORTHEAST OF

WATERTOWN SOUTH DAKOTA.  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.



DISCUSSION...SCTD TSTMS EXPECTED TO INCREASE ALONG AND N OF STALLED

FRONT IN NRN SD AS ASCENT ASSOCIATED WITH APPROACHING IMPULSE IN

WNWLY UPR FLOW OVERSPREADS REGION.  AREA OF FAIRLY RICH BOUNDARY

LAYER MOISTURE IS SURMOUNTED BY STEEP MID LEVEL LAPSE RATES.  ALONG

WITH MODEST BUT DEEPLY VEERING WIND PROFILES...SETUP APPEARS

FAVORABLE FOR STRONG ...SEMI-DISCRETE UPDRAFTS WITH A POTENTIAL FOR

LARGE HAIL AND LOCALLY DAMAGING WIND.



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 500. MEAN STORM

MOTION VECTOR 28025.





...CORFIDI

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