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147 

WWUS20 KWNS 301902

SEL3

SPC WW 301902

MTZ000-WYZ000-310100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 633

NWS STORM PREDICTION CENTER NORMAN OK

105 PM MDT MON AUG 30 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF SOUTHEASTERN MONTANA

       NORTHEASTERN WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 105 PM UNTIL 700

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 70

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

NORTHWEST OF WORLAND WYOMING TO 80 MILES EAST OF GILLETTE

WYOMING.  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.



DISCUSSION...THUNDERSTORMS ARE INCREASING AHEAD OF VIGOROUS TROUGH

MOVING ACROSS CENTRAL WY ATTM.  WITH MLCAPES TO 1000 J/KG AND LOW

LEVEL CONVERGENCE E OF BIG HORN MTNS...EXPECT SEVERE THUNDERSTORM

POTENTIAL TO INCREASE EWD ACROSS THE WATCH THRU THE AFTERNOON

HEATING PERIOD.



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 24025.





...HALES

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