WATCHES: Severe Thunderstorm Watch Number 728

WWUS20 KWNS 042252
SEL8
SPC WW 042252
MTZ000-NDZ000-050400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 728
NWS STORM PREDICTION CENTER NORMAN OK
450 PM MDT THU AUG 4 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

EXTREME EASTERN MONTANA
WESTERN NORTH DAKOTA

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 450 PM UNTIL
1000 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 60 MILES WEST
NORTHWEST OF MINOT NORTH DAKOTA TO 40 MILES SOUTHEAST OF BAKER
MONTANA. 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 727...

DISCUSSION...STORMS ARE SLOWING INCREASING OVER ERN MT WITH ONE
SPLITTING SUPERCELL EVIDENT OVER DAWSON COUNTY. ACTIVITY IS FOCUSED
NEAR AN EAST/WEST FRONT AND WEAK LOW LEVEL CONVERGENCE ZONE
EXTENDING ACROSS THE AREA. STEEP LAPSE RATES AND SURFACE DEW POINTS
IN THE UPPER 50S ARE CONTRIBUTING TO MLCAPE AROUND 1500 J/KG.
WESTERLY MID/UPPER LEVEL WINDS OF 30-50 KT ARE PROVIDING SUFFICIENT
VERTICAL SHEAR...PARTICULARLY ALONG/NORTH OF THE BOUNDARY...FOR
ORGANIZED STORMS INCLUDING POTENTIAL FOR ADDITIONAL SUPERCELLS.
ACTIVITY IS EXPECTED TO SPREAD EWD INTO WRN ND THIS EVENING BEFORE
WEAKENING AFTER SUNSET.

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.

...WEISS

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