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501 

WWUS20 KWNS 122039

SEL9

SPC WW 122039

NDZ000-SDZ000-130400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 289

NWS STORM PREDICTION CENTER NORMAN OK

340 PM CDT TUE MAY 12 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       MUCH OF CENTRAL AND SOUTHWESTERN NORTH DAKOTA

       PARTS OF NORTHWESTERN SOUTH DAKOTA



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 340 PM UNTIL

1100 PM CDT.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 105

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES WEST

SOUTHWEST OF BUFFALO SOUTH DAKOTA TO 85 MILES EAST NORTHEAST OF

BISMARCK NORTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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...DEEPENING SURFACE LOW WRN DAKOTAS AHEAD OF STRONG

UPSTREAM TROUGH AND JET STREAM.  THUNDERSTORMS DEVELOPING ALONG COLD

FRONTAL BOUNDARY NWRN ND INTO NERN WY AND EXPECTED TO RAPIDLY

INCREASE IN NUMBER AND INTENSITY.  STORMS SHOULD EVOLVE INTO A

SQUALL LINE BY THIS EVENING AND MOVE RAPIDLY NEWD ACROSS THE WATCH

AS UPPER WINDS INCREASE.  DAMAGING WINDS WILL BE THE PRIMARY THREAT

MOST LIKELY ASSOCIATED WITH THE SQUALL LINE THIS EVENING.  EARLY

PART OF WATCH LARGE HAIL WILL ALSO BE A THREAT.



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

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

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

MOTION VECTOR 24040.





...HALES

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