WWUS20 KWNS 112250
SEL9
SPC WW 112250
MTZ000-NDZ000-120600-
URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 599
NWS STORM PREDICTION CENTER NORMAN OK
450 PM MDT WED AUG 11 2010
THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
NORTH CENTRAL AND NORTHEAST MONTANA
NORTHWEST NORTH DAKOTA
EFFECTIVE THIS WEDNESDAY AFTERNOON FROM 450 PM UNTIL MIDNIGHT MDT.
HAIL TO 2.5 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 65
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTH
SOUTHWEST OF HAVRE MONTANA TO 30 MILES EAST SOUTHEAST OF MINOT
NORTH DAKOTA. 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.
DISCUSSION...STRONG/SEVERE THUNDERSTORMS HAVE DEVELOPED RECENTLY IN
CENTRAL MT AND SHOULD EXPAND IN COVERAGE/INTENSITY THROUGH THE
EVENING ACROSS NE MT AND NW ND...IN ADVANCE OF AN EJECTING MIDLEVEL
TROUGH OVER THE NRN ROCKIES. THE STORMS WILL MOVE EWD ALONG A
STALLED FRONT WITH MODEST BOUNDARY LAYER MOISTURE AND STEEP LAPSE
RATES CONTRIBUTING TO MLCAPE NEAR 2000 J/KG ON THE COOL SIDE OF THE
BOUNDARY...WHERE VERTICAL SHEAR IS SUFFICIENT FOR SUPERCELLS. LARGE
HAIL SHOULD BE THE MAIN THREAT INITIALLY IN MT...WHILE THE DAMAGING
WIND THREAT SHOULD INCREASE LATER THIS EVENING/TONIGHT AS STORM
MERGERS/INTERACTIONS PROMOTE UPSCALE GROWTH INTO A CLUSTER OR TWO.
AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 27020.
...THOMPSON
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