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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 569

NWS STORM PREDICTION CENTER NORMAN OK

315 PM CDT WED AUG 4 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL ILLINOIS

       CENTRAL AND NORTHEAST MISSOURI



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 315 PM UNTIL

1000 PM CDT.



HAIL TO 1.5 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 45

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 60 MILES WEST

SOUTHWEST OF KNOB NOSTER MISSOURI TO 10 MILES SOUTH OF DANVILLE

ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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 567...WW 568...



DISCUSSION...VISIBLE IMAGERY SUGGESTS THAT THUNDERSTORM DEVELOPMENT

WILL LIKELY OCCUR WITHIN THE NEXT 1-2 HOURS ALONG THE SURFACE FRONT

MOVING SEWD FROM NW INTO CENTRAL MO...AS WELL AS FARTHER E ALONG A

REMNANT OUTFLOW BOUNDARY/DIFFERENTIAL HEATING ZONE INTO CENTRAL IL.

THE MODIFIED 18Z ILX SOUNDING REVEALS 4000 J/KG MLCAPE AND LITTLE

CONVECTIVE INHIBITION...AND WEAK BACKGROUND ASCENT MAY ALSO BE

OCCURRING IN ASSOCIATION WITH REMNANT MCV/S MOVING EWD OVER NW MO

AND SE IA.  THE COMBINATION OF STRONG INSTABILITY AND EFFECTIVE BULK

SHEAR OF 30-40 KT WILL SUPPORT ORGANIZED MULTICELL CLUSTERS...AND

POTENTIALLY SOME MARGINAL SUPERCELL STRUCTURES...CAPABLE OF

PRODUCING DAMAGING WINDS/HAIL THROUGH LATE EVENING.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 27030.





...THOMPSON

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