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000 

WWUS20 KWNS 091814

SEL5

SPC WW 091814

IDZ000-MTZ000-100200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 815

NWS STORM PREDICTION CENTER NORMAN OK

1215 PM MDT SAT AUG 9 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL IDAHO

       WESTERN MONTANA



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1215 PM UNTIL

800 PM MDT.



HAIL TO 1.5 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 85

STATUTE MILES EITHER SIDE OF A LINE FROM 25 MILES WEST OF SALMON

IDAHO TO 55 MILES EAST SOUTHEAST OF CUT BANK MONTANA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU5).



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 EXPECTED TO CONTINUE INCREASING AND

INTENSIFYING ACROSS WW THIS AFTERNOON AHEAD OF NEGATIVELY-TILTED

SHORTWAVE TROUGH CURRENTLY EJECTING ACROSS THE PAC NW.  CONTINUED

HEATING WITHIN SEASONABLY MOIST AIR MASS IS EXPECTED TO SUPPORT

MARGINAL TO MODERATE INSTABILITY AND STEEP LOW LEVEL LAPSE RATES

AHEAD OF CONVECTION MOVING NEWD.  DAMAGING WINDS AND LARGE HAIL CAN

BOTH BE EXPECTED AS SHEAR REMAINS SUPPORTIVE OF LINES/BRIEF

SUPERCELLS.



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

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400. MEAN STORM

MOTION VECTOR 24035.





...EVANS

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