SEL9 URGENT - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WATCH NUMBER 359 NWS STORM PREDICTION CENTER NORMAN OK 140 PM MDT TUE JUN 5 2012 THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF SOUTHWEST AND CENTRAL MONTANA EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 140 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 50 MILES SOUTH OF LIVINGSTON MONTANA TO 55 MILES NORTH OF BOZEMAN 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 358... DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY THIS AFTERNOON ALONG THE HIGH TERRAIN AS LARGE-SCALE FORCING FOR ASCENT STRENGTHENS FROM THE SW. AMBIENT AIR MASS IS CHARACTERIZED BY STEEP LAPSE RATES AND DEWPOINTS IN THE MID 40S-LOW 50S WITH RESULTING SBCAPE OF 500-1000 J/KG. VERTICAL SHEAR IS ALSO FORECAST TO STRENGTHEN MARKEDLY LATE THIS AFTERNOON INTO EVENING IN CONJUNCTION WITH ARRIVAL OF NEGATIVELY TILTED MIDLEVEL TROUGH. AS SUCH...THE THREAT FOR ORGANIZED STORM MODES...INCLUDING SUPERCELLS WILL INCREASE WITH A RISK FOR DAMAGING WINDS AND LARGE HAIL. 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 17035.
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