

000 

WWUS20 KWNS 211955

SEL3

SPC WW 211955

SDZ000-WYZ000-220400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 283

NWS STORM PREDICTION CENTER NORMAN OK

255 PM CDT MON MAY 21 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN AND CENTRAL SOUTH DAKOTA

       NORTHEAST WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 255 PM UNTIL

1100 PM 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 90

STATUTE MILES EAST AND WEST OF A LINE FROM 70 MILES WEST

NORTHWEST OF MOBRIDGE SOUTH DAKOTA TO 70 MILES SOUTH OF RAPID

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

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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 282...



DISCUSSION...TSTMS/POSSIBLE SUPERCELLS EXPECTED TO FORM IN THE NEXT

HOUR OR SO BOTH INVOF THE BLACK HILLS AND ALONG NNE/SSW PREFRONTAL

TROUGH IN WRN PART OF WW.  ENVIRONMENT IN NRN HALF OF WW IS MORE

LIKE THAT IN ND...AND SHOULD SUPPORT A FEW SUSTAINED STORMS WITH

HAIL/WIND AND POSSIBLY A BRIEF TORNADO BEFORE ACTIVITY CONGEALS INTO

A BROKEN LINE.  FARTHER S...SETUP APPEARS MORE CONDUCIVE TO CLUSTERS

OF HIGH-BASED ACTIVITY WITH A THREAT FOR HIGH WIND FROM FORWARD

PROPAGATING BOWING SEGMENTS.



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 22025.





...CORFIDI

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