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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 264

NWS STORM PREDICTION CENTER NORMAN OK

300 PM CDT SAT MAY 7 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EAST CENTRAL ILLINOIS

       WESTERN AND CENTRAL INDIANA



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 300 PM UNTIL

1000 PM 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 70

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST

NORTHWEST OF BLOOMINGTON ILLINOIS TO 35 MILES EAST NORTHEAST OF

INDIANAPOLIS INDIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).



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...EXPECT STORM DEVELOPMENT TO CONTINUE TO INCREASE OVER

THE NEXT FEW HOURS AS UPPER SHORT WAVE TROUGH AND ASSOCIATED SURFACE

LOW TRACK ESEWD ACROSS THE WATCH AREA. STORMS WILL BE DEVELOPING

WITHIN MODERATELY UNSTABLE AIRMASS WHERE SBCAPE WILL BE AROUND 1000

J PER KG. 50-60KT MID LEVEL WIND MAX ATOP LOW LEVEL SLY FLOW SHOULD

CONTRIBUTE TO EFFECTIVE SHEAR SUPPORTIVE OF PERSISTENT ROTATING

UPDRAFTS CAPABLE OF PRODUCING LARGE HAIL. GENERALLY WEAK LOW LEVEL

SHEAR SHOULD OFFSET TORNADO THREAT BUT AN ISOLATED/LOW PROBABILITY

POTENTIAL FOR A WEAK/BRIEF TORNADO MAY EVOLVE NEAR THE WEAK SURFACE

LOW...AND ALONG OUTFLOW-REINFORCED WARM FRONT ACROSS NRN PORTIONS OF

THE WATCH.



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 400. MEAN STORM

MOTION VECTOR 30025.





...CARBIN

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