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949 

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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