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000 

WWUS20 KWNS 202025

SEL9

SPC WW 202025

IDZ000-MTZ000-210300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 429

NWS STORM PREDICTION CENTER NORMAN OK

225 PM MDT WED JUN 20 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL IDAHO

       WESTERN MONTANA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 225 PM UNTIL

900 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 110

STATUTE MILES EAST AND WEST OF A LINE FROM 80 MILES NORTH

NORTHEAST OF MISSOULA MONTANA TO 30 MILES EAST SOUTHEAST OF

DILLON MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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 428...



DISCUSSION...STORMS ARE EXPECTED TO INCREASE IN INTENSITY AND

COVERAGE INTO THE EVENING HOURS...AS AN UPPER LEVEL IMPULSE IN NRN

NV APPROACHES THE REGION. STEEP MID LEVEL LAPSE RATES AND 40-50 KT

DEEP LAYER SHEAR WILL BE SUFFICIENT FOR SUPERCELLS. ALTHOUGH SOME

HAIL IS EXPECTED... THE WELL MIXED AND DEEP BOUNDARY LAYER INDICATES

THAT WIND DAMAGE SHOULD BE THE MAIN THREAT.



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.





...IMY

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