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000 

WWUS20 KWNS 122012

SEL7

SPC WW 122012

MTZ000-130400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 267

NWS STORM PREDICTION CENTER NORMAN OK

210 PM MDT SAT MAY 12 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN AND CENTRAL MONTANA



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 210 PM UNTIL

1000 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 105

STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES WEST

SOUTHWEST OF BOZEMAN MONTANA TO 75 MILES 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.



DISCUSSION...DEEP MOIST CONVECTION CONTINUES TO INCREASE OVER HIGHER

TERRAIN ACROSS W-CENTRAL/SWRN MT EARLY THIS AFTERNOON...LIKELY AIDED

BY SUBTLE SHORTWAVE TROUGHS ROTATING NEWD INTO THE NRN ROCKIES.  AIR

MASS IS DESTABILIZING AHEAD OF THIS ACTIVITY OVER LOWER ELEVATIONS

WHERE MLCAPE AROUND 1500 J/KG AND WEAK CINH IS ALREADY IN PLACE.

SHEAR WILL REMAIN MORE THAN ADEQUATE FOR SUPERCELLS...AND POSSIBLY

SMALL LINES AS ACTIVITY BUILDS UPSCALE AND MOVES NEWD THROUGH THE

EVENING.  LARGE HAIL AND ISOLATED DAMAGING WINDS CAN BE EXPECTED

WITH STRONGER STORMS.



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 500. MEAN STORM

MOTION VECTOR 22025.





...EVANS

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