

749 

WWUS20 KWNS 061839

SEL7

SPC WW 061839

IDZ000-MTZ000-NVZ000-070300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 667

NWS STORM PREDICTION CENTER NORMAN OK

1235 PM MDT THU AUG 6 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN AND CENTRAL IDAHO

       WESTERN MONTANA

       NORTHEAST NEVADA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1235 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 85

STATUTE MILES EAST AND WEST OF A LINE FROM 65 MILES SOUTHEAST OF

OWYHEE NEVADA TO 5 MILES NORTH NORTHEAST OF GREAT FALLS MONTANA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 666...



DISCUSSION...ISOLATED STRONG/SEVERE THUNDERSTORMS DEVELOPED THIS

MORNING FROM NERN NV INTO CENTRAL ID...AND ADDITIONAL SEVERE STORMS

ARE LIKELY TO DEVELOP THIS AFTERNOON AND EVENING AND SPREAD NEWD

WITH TIME IN RESPONSE TO INCREASING DYNAMIC FORCING IN ADVANCE OF

THE NRN CA UPPER LOW.  VISIBLE IMAGERY INDICATES CLEAR SKIES FROM

NERN NV ACROSS SWRN MT IMMEDIATELY EAST OF THE FRONTAL BAND...AND

STRONG HEATING AND DESTABILIZATION IS EXPECTED TO OCCUR THIS

AFTERNOON.  STRONG SWLY FLOW ALOFT AND DEEP LAYER SHEAR OF 40-50 KT

IN THE LOWEST 6 KM AGL WILL ENHANCE STORM ORGANIZATION AND

INTENSITY...WITH POTENTIAL FOR SUPERCELLS AND BOWING LINE SEGMENTS

TO DEVELOP.  DAMAGING WINDS AND LARGE WILL BE THE 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 500. MEAN STORM

MOTION VECTOR 23035.





...WEISS

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