IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WATCH NUMBER 428 NWS STORM PREDICTION CENTER NORMAN OK 310 PM MDT MON JUN 25 2012 THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF SOUTHEAST MONTANA WESTERN SOUTH DAKOTA EASTERN WYOMING EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 310 PM UNTIL 1100 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 70 STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHWEST OF MILES CITY MONTANA TO 135 MILES SOUTHEAST OF GILLETTE WYOMING. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8). 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 426...WW 427... DISCUSSION...TSTMS ARE DEVELOPING THIS AFTERNOON ALONG THE HIGH TERRAIN WITHIN A HOT...DEEPLY MIXED BOUNDARY LAYER...PERHAPS IN RESPONSE TO A WEAK MIDLEVEL IMPULSE CRESTING RIDGE AXIS. AIR MASS MOISTENS/DESTABILIZES WITH EWD/NEWD EXTENT ACROSS THE WATCH AREA...THOUGH CAP ALSO INCREASES. SHOULD STORMS BECOME ROOTED IN THE PROGRESSIVELY MORE UNSTABLE ENVIRONMENT...THE PRESENCE OF 30-40 KT OF DEEP-LAYER SHEAR WILL SUPPORT ORGANIZED STORM STRUCTURES INCLUDING SUPERCELLS 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 500. MEAN STORM MOTION VECTOR 27020. ...MEAD
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