WATCHES: Severe Thunderstorm Watch Number 668

WWUS20 KWNS 062100
SEL8
SPC WW 062100
MTZ000-WYZ000-070400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 668
NWS STORM PREDICTION CENTER NORMAN OK
300 PM MDT THU AUG 6 2009

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

SOUTH CENTRAL MONTANA
NORTHWEST WYOMING

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 300 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 60
STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES EAST
NORTHEAST OF HARLOWTON MONTANA TO 50 MILES EAST OF JACKSON
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 666...WW 667...

DISCUSSION...STRONG SEVERE STORMS HAVE DEVELOPED IN A BAND FROM
EXTREME SERN ID NNEWD INTO SRN MT. THIS ACTIVITY IS AHEAD OF A
STRONG UPPER LOW MOVING ENEWD INTO THE GREAT BASIN...AND INCREASING
DYNAMIC FORCING IS FORECAST TO SPREAD DOWNSTREAM TOWARD THE NRN
ROCKIES THIS EVENING. LOW LEVEL MOISTURE WITH SURFACE DEW POINTS IN
THE UPPER 50S IS CONTRIBUTING TO MLCAPE OF 1000-1500 J/KG...AND
WSWLY MID LEVEL WINDS OF 40-45 KT ARE RESULTING IN DEEP LAYER SHEAR
SUPPORTIVE OF SEVERE STORMS INCLUDING ISOLATED SUPERCELLS. LARGE
HAIL AND DAMAGING WINDS WILL BE POSSIBLE WITH STRONGER STORMS.

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 24030.

...WEISS

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