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   URGENT - IMMEDIATE BROADCAST REQUESTED
   SEVERE THUNDERSTORM WATCH NUMBER 510
   NWS STORM PREDICTION CENTER NORMAN OK
   225 PM MDT TUE JUN 21 2005
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
   
          CENTRAL AND NORTHERN MONTANA
   
   EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 225 PM UNTIL
   1000 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 120
   STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHEAST OF
   CUT BANK MONTANA TO 60 MILES SOUTHEAST OF HELENA MONTANA.  FOR A
   COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
   UPDATE (WOUS64 KWNS WOU0).
   
   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 WILL DEVELOP OVER THE HIGHER TERRAIN OF
   SW/CENTRAL MT THE NEXT 1-2 HOURS AND SPREAD NEWD TOWARD N CENTRAL MT
   THIS AFTERNOON/EVENING.  ACTIVITY WILL BE ENHANCED BY A WEAK MID
   LEVEL TROUGH AND MOISTURE PLUME MOVING NNEWD FROM ID.  DEEP MIXED
   LAYERS WILL SUPPORT A THREAT OF DAMAGING WINDS ACROSS THE SW PART OF
   WW...WHILE STRONG INSTABILITY AND DEEP LAYER VERTICAL SHEAR WILL
   SUPPORT BOTH SUPERCELLS WITH LARGE HAIL AND BOW ECHOES AS STORMS
   EVOLVE/MERGE.  THE LOCAL ENVIRONMENT NEAR THE CANADIAN BORDER MAY
   SUPPORT AN ISOLATED TORNADO...THOUGH THIS THREAT WILL TEND TO SHIFT
   NWD INTO SASKATCHEWAN DURING THE EVENING.
   
   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 24025.
   
   
   ...THOMPSON