WATCHES: Severe Thunderstorm Watch Number 550

WWUS20 KWNS 260038
SEL0
SPC WW 260038
ILZ000-MOZ000-260700-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 550
NWS STORM PREDICTION CENTER NORMAN OK
740 PM CDT SAT JUN 25 2011

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

SOUTHWEST ILLINOIS
CENTRAL AND SOUTHEAST MISSOURI

EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 740 PM
UNTIL 200 AM CDT.

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 60
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 65 MILES WEST
SOUTHWEST OF COLUMBIA MISSOURI TO 15 MILES EAST NORTHEAST OF CAPE
GIRARDEAU MISSOURI. FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).

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...SLIGHTLY ELEVATED CONVECTION IS DEVELOPING ALONG AND
JUST N OF THE SURFACE WARM FRONT ACROSS CENTRAL/E CENTRAL MO. A
FEED OF STRONG INSTABILITY ALONG THE BOUNDARY AND EFFECTIVE BULK
SHEAR IN EXCESS OF 40 KT WILL BE FAVORABLE FOR SUPERCELLS. AN
ISOLATED TORNADO CANNOT BE RULED OUT GIVEN THE STRONG LOW-LEVEL
SHEAR ALONG THE BOUNDARY...BUT THE SLIGHTLY ELEVATED NATURE OF THE
STORM INITIATION SUGGESTS THAT LARGE HAIL AND DAMAGING WINDS WILL BE
THE MAIN THREATS. OVERNIGHT...CONVECTION MAY EVOLVE INTO AN MCS
WITH A CONTINUING THREAT 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 550. MEAN STORM
MOTION VECTOR 30025.

...THOMPSON

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