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WWUS20 KWNS 050224

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SPC WW 050224

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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 230

NWS STORM PREDICTION CENTER NORMAN OK

925 PM CDT FRI MAY 4 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHEAST NEBRASKA

       EASTERN SOUTH DAKOTA



EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 925 PM

UNTIL 400 AM CDT.



TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS

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



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE

MILES EAST AND WEST OF A LINE FROM 75 MILES SOUTH SOUTHWEST OF

MITCHELL SOUTH DAKOTA TO 45 MILES NORTH NORTHWEST OF BROOKINGS

SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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...THIS TORNADO WATCH REPLACES TORNADO

WATCH NUMBER 226. WATCH NUMBER 226 WILL NOT BE IN EFFECT AFTER

925 PM CDT. CONTINUE...WW 227...WW 228...WW 229...



DISCUSSION...SW/NE ORIENTED INVERTED TROUGH EXPECTED TO REMAIN A

FOCUS FOR STORM/POSSIBLE SUPERCELL DEVELOPMENT THROUGH EARLY

SATURDAY FROM N CNTRL NEB INTO E CNTRL SD.  WHILE LEAD UPPER IMPULSE

THAT WAS IN PART RESPONSIBLE FOR STORMS NOW OVER THE REGION IS

LIFTING NNE INTO ND...TRAILING SFC COOL AIR SURGE AND NOCTURNAL

STRENGTHENING OF LLJ WILL MAINTAIN FAVORABLE ENVIRONMENT FOR LOW

LEVEL UPDRAFT DEVELOPMENT AND ROTATION.  THUS THREAT MAY PERSIST FOR

ISOLATED TORNADOES/LOCALLY DAMAGING WIND DESPITE LOSS OF SFC

HEATING.



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

SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND

GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.

MEAN STORM MOTION VECTOR 20030.





...CORFIDI

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