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WWUS20 KWNS 061933

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SPC WW 061933

IDZ000-MTZ000-WYZ000-070300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 554

NWS STORM PREDICTION CENTER NORMAN OK

135 PM MDT MON JUL 6 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EASTERN IDAHO

       PARTS OF SOUTHWEST AND CENTRAL MONTANA

       NORTHWEST WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 135 PM UNTIL 900

PM MDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 185

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES SOUTH OF

DRUMMOND MONTANA TO 55 MILES EAST OF HARLOWTON MONTANA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU4).



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 553...



DISCUSSION...A POTENT AND WELL-DEFINED SHORT WAVE TROUGH AND

ASSOCIATED COLD FRONT WILL MOVE ACROSS THE ROCKIES AND ENCOUNTER AN

INCREASINGLY UNSTABLE AIRMASS ALONG AND EAST OF THE CONTINENTAL

DIVIDE THIS AFTERNOON. AS THE SYNOPTIC FORCING ACTS TO STEEPEN MID

LAPSE RATES...BOUNDARY LAYER MOISTENING/WARMING WILL CONTRIBUTE TO

MLCAPE IN THE 800-1200 J/KG RANGE...MORE THAN ADEQUATE TO SUPPORT

ROBUST STORM UPDRAFTS IN THE PRESENCE OF INCREASINGLY STRONG SHEAR

AND LARGER SCALE DYNAMICS.

INITIALLY QUASI-DISCRETE CELLS/SUPERCELLS WILL BECOME INCREASINGLY

FOCUSED AND TAKE ON LINEAR CHARACTERISTICS AS COLD FRONT BECOMES

BETTER DEFINED EAST OF THE HIGHER TERRAIN LATER TODAY. A FEW OF

THESE STORMS COULD PRODUCE LARGE HAIL AND POSSIBLY EVEN A BRIEF/WEAK

TORNADO BEFORE ACTIVITY MERGES AND EVOLVES INTO A SEVERE SQUALL LINE

WITH WIDESPREAD DAMAGING WINDS BECOMING MORE OF A THREAT WITH TIME.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM

MOTION VECTOR 26035.





...CARBIN

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