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WWUS20 KWNS 241720

SEL7

SPC WW 241720

ILZ000-MOZ000-250100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 647

NWS STORM PREDICTION CENTER NORMAN OK

1220 PM CDT FRI AUG 24 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL ILLINOIS

       CENTRAL MISSOURI



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 1220 PM UNTIL

800 PM CDT.



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 75

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST

NORTHWEST OF FORT LEONARD WOOD MISSOURI TO 35 MILES EAST

SOUTHEAST OF CHAMPAIGN ILLINOIS.  FOR A COMPLETE DEPICTION OF THE

WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 EXPECTED TO BECOME MORE WIDESPREAD

AND INCREASE IN INTENSITY THIS AFTERNOON AHEAD OF SLOW MOVING MID

LEVEL SYSTEM MOVING NEWD OUT OF CENTRAL MO.  SURFACE OUTFLOW

BOUNDARY WILL PROVIDE ADDITIONAL FOCUS FOR THUNDERSTORM DEVELOPMENT

AHEAD OF THIS IMPULSE THROUGH THE AFTERNOON.  AIR MASS IS ALREADY

MODERATELY UNSTABLE INTO SERN MO/SRN IL...WITH INSTABILITY AXIS

EXPECTED TO BUILD NNEWD WITH TIME.  SHEAR REMAINS QUITE STRONG AND

WILL BE SUPPORTIVE OF SUPERCELLS...ALTHOUGH OVERALL EVOLUTION INTO

ONE OR MORE BOW ECHOES IS EXPECTED THROUGH THE EARLY EVENING.

DAMAGING WINDS SHOULD BE PRIMARY SEVERE THREAT...ALTHOUGH ISOLATED

LARGE HAIL CAN ALSO BE EXPECTED WITH THE MORE INTENSE CELLS.



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 26035.





...EVANS

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