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000 

WWUS20 KWNS 042005

SEL6

SPC WW 042005

IDZ000-MTZ000-050400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 656

NWS STORM PREDICTION CENTER NORMAN OK

205 PM MDT FRI JUL 4 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       LEMHI COUNTY IDAHO

       WESTERN INTO CENTRAL MONTANA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 205 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 80

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTHEAST OF

CUT BANK MONTANA TO 40 MILES WEST OF DILLON MONTANA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU6).



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 INCREASE IN COVERAGE AND INTENSITY

THROUGH THE REST OF THE AFTERNOON/EARLY EVENING AHEAD OF SHORTWAVE

TROUGH NOW MOVING INTO THE NRN ROCKIES.  AIR MASS IS ALREADY

MODERATELY UNSTABLE OVER SWRN MT...AND WILL DESTABILIZE AND BECOME

WEAKLY CAPPED OVER LOWER ELEVATIONS OF CENTRAL MT OVER THE NEXT FEW

HOURS.  DEEP LAYER SHEAR WILL SUPPORT SUPERCELLS...WITH EVENTUAL

EVOLUTION INTO ONE OR MORE LINEAR STRUCTURES AS SURFACE COLD FRONT

PUSHES EAST OF THE MOUNTAINS THIS EVENING.  LARGE HAIL AND DAMAGING

WINDS ARE EXPECTED TO BE PRIMARY SEVERE THREATS.



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.





...EVANS

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