WATCHES: Severe Thunderstorm Watch Number 783

WWUS20 KWNS 172041
SEL3
SPC WW 172041
COZ000-KSZ000-NEZ000-SDZ000-180300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 783
NWS STORM PREDICTION CENTER NORMAN OK
240 PM MDT WED AUG 17 2011

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

NORTHEAST COLORADO
NORTHWEST KANSAS
WESTERN AND CENTRAL NEBRASKA
SOUTH CENTRAL SOUTH DAKOTA

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 240 PM UNTIL
900 PM 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 80
STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES NORTH
NORTHWEST OF VALENTINE NEBRASKA TO 15 MILES SOUTH OF BURLINGTON
COLORADO. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

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...THUNDERSTORMS ARE ALREADY DEVELOPING IN NE CO...AND NEW
DEVELOPMENT WILL BE POSSIBLE IN THE NEXT COUPLE OF HOURS FARTHER N
ACROSS NEB/SD ALONG THE SURFACE LEE TROUGH. WEAKENING CONVECTIVE
INHIBITION...MLCAPE OF 2000-3000 J/KG...AND EFFECTIVE BULK SHEAR OF
40-50 KT WILL SUPPORT SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND
DAMAGING WINDS. AN ISOLATED TORNADO CANNOT BE RULED OUT INVOF NW
KS/SW NEB WHERE LOW-LEVEL MOISTURE WILL BE MAXIMIZED AND 0-1 KM SRH
WILL APPROACH 100 M2/S2. LATER THIS EVENING...STORM MERGERS COULD
LEAD TO UPSCALE GROWTH INTO ONE OR TWO SMALL CLUSTERS...WITH AN
ATTENDANT RISK FOR DAMAGING WINDS.

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 29020.

...THOMPSON

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