

000 

WWUS20 KWNS 242047

SEL3

SPC WW 242047

MTZ000-SDZ000-WYZ000-250300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 603

NWS STORM PREDICTION CENTER NORMAN OK

245 PM MDT TUE JUN 24 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME SOUTHEAST MONTANA

       WESTERN AND NORTHWESTERN SOUTH DAKOTA

       EXTREME NORTHEAST WYOMING



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 245 PM UNTIL

900 PM MDT.



HAIL TO 2.5 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 95

STATUTE MILES EAST AND WEST OF A LINE FROM 10 MILES WEST

NORTHWEST OF LEMMON SOUTH DAKOTA TO 40 MILES WEST SOUTHWEST 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 602...



DISCUSSION...SCATTERED THUNDERSTORMS WILL LIKELY DEVELOP SWD ALONG A

PRE-FRONTAL TROUGH FROM SE MT INTO NE WY IN THE NEXT COUPLE OF

HOURS...WITH ADDITIONAL DEVELOPMENT POSSIBLE OVER THE BLACK HILLS IN

SD.  MODERATE INSTABILITY IS PRESENT IN THE WARM SECTOR AND VERTICAL

SHEAR IS SUFFICIENT FOR SUPERCELLS ALONG THE SRN PERIPHERY OF THE

STRONGER MID LEVEL FLOW OVER NW SD...WITH WEAKER VERTICAL SHEAR TO

THE SOUTH.  WHILE AN ISOLATED TORNADO CANNOT BE RULED OUT ACROSS NW

SD THIS AFTERNOON...THE PRIMARY SEVERE THREATS SHOULD BE LARGE HAIL

AND DAMAGING WINDS.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 27020.





...THOMPSON

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