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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 631

NWS STORM PREDICTION CENTER NORMAN OK

440 PM EDT FRI SEP 7 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EAST CENTRAL ILLINOIS

       PARTS OF CENTRAL AND SOUTHERN INDIANA

       EXTREME NORTHERN KENTUCKY

       SOUTHWEST OHIO



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 440 PM UNTIL

1100 PM EDT.



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 35

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 75 MILES WEST

SOUTHWEST OF MATTOON ILLINOIS TO 25 MILES SOUTHEAST OF COLUMBUS

OHIO.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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...THIS SEVERE THUNDERSTORM WATCH REPLACES

SEVERE THUNDERSTORM WATCH NUMBER 628. WATCH NUMBER 628 WILL NOT

BE IN EFFECT AFTER 440 PM EDT. CONTINUE...WW 629...WW 630...



DISCUSSION...SCATTERED STRONG/SEVERE STORMS WILL PERSIST ALONG A

SLOW-MOVING OUTFLOW BOUNDARY ACROSS INDIANA/OH...AIDED BY MODERATE

INSTABILITY S OF THE BOUNDARY AND AN INCREASE IN VERTICAL SHEAR WITH

NWD EXTENT FROM THE OH RIVER.  OTHER STORMS WILL ALSO INCREASE IN

COVERAGE/INTENSITY ACROSS CENTRAL IL AS LARGE SCALE ASCENT SPREADS

EWD/SEWD IN ADVANCE OF THE AMPLIFYING MIDLEVEL TROUGH APPROACHING

THE MID MS VALLEY.  DAMAGING WINDS AND ISOLATED LARGE HAIL WILL BE

THE MAIN THREATS.



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 500. MEAN STORM

MOTION VECTOR 28030.





...THOMPSON

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