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285 

WWUS20 KWNS 072255

SEL3

SPC WW 072255

SDZ000-080500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 673

NWS STORM PREDICTION CENTER NORMAN OK

455 PM MDT FRI AUG 7 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN SOUTH DAKOTA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 455 PM UNTIL

1100 PM MDT.



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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHEAST OF

BUFFALO SOUTH DAKOTA TO 75 MILES SOUTH SOUTHEAST 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 672...



DISCUSSION...THUNDERSTORMS WILL CONTINUE DEVELOPING ENEWD ACROSS WRN

SD THROUGH THE EVENING AHEAD OF LARGE UPPER LOW OVER THE NRN

ROCKIES.  REGION REMAINS WITHIN NLY SFC FLOW IN WAKE OF A SURFACE

COLD FRONT...HOWEVER SUFFICIENT INSTABILITY REMAINS FOR ROBUST

THUNDERSTORM DEVELOPMENT...DESPITE BECOMING SOMEWHAT ELEVATED.

SHEAR WILL ALSO REMAIN SUPPORTIVE OF SUPERCELLS...WITH SPLITTING

STORMS LIKELY GIVEN LARGE STRAIGHT HODOGRAPHS.  MOST LIKELY AREA

WILL BE INTO NWRN SD THIS EVENING...ALTHOUGH DEEP MIXING MAY ALSO

SUPPORT ISOLATED SEVERE THUNDERSTORMS NEAR THE NEB BORDER.



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 450. MEAN STORM

MOTION VECTOR 23030.





...EVANS

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