SEL0 URGENT - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WATCH NUMBER 340 NWS STORM PREDICTION CENTER NORMAN OK 210 PM MDT SAT JUN 2 2012 THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF SOUTH-CENTRAL AND EASTERN MONTANA EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 210 PM UNTIL 900 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 95 STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES NORTH NORTHWEST OF BOZEMAN MONTANA TO 25 MILES NORTH OF BAKER MONTANA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0). 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...TSTMS ARE EXPECTED TO INCREASE IN BOTH COVERAGE AND INTENSITY ACROSS PARTS OF CNTRL...SRN AND ERN MT THROUGH THE LATE AFTERNOON AND INTO THE EVENING. MID/UPPER LEVEL HEIGHT FALLS WILL ACT TO SUPPRESS RIDGE AXIS ACROSS THE REGION WITH SUBSEQUENT LARGE SCALE ASCENT ACTING ON A MOIST AND WEAKLY UNSTABLE AIRMASS SUFFICIENT TO RESULT IN SCATTERED VIGOROUS CONVECTION. DEEP-LAYER SHEAR SHOULD ALLOW FOR UPDRAFT PERSISTENCE AND SOME ORGANIZATION WITH CELLS AND/OR SHORT LINE SEGMENTS POSING A THREAT FOR SEVERE HAIL AND HIGH WINDS. STORMS MAY CONGEAL ACROSS PORTIONS OF ERN MT DURING THE EVENING WITH WIND POTENTIAL POSSIBLY INCREASING OVER THESE AREAS. 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 25025.
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