WATCHES: Severe Thunderstorm Watch Number 508

WWUS20 KWNS 312047
SEL8
SPC WW 312047
ILZ000-INZ000-010300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 508
NWS STORM PREDICTION CENTER NORMAN OK
345 PM CDT SAT AUG 31 2013

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
PARTS OF CENTRAL AND SOUTHERN ILLINOIS
WEST CENTRAL AND SOUTHWESTERN INDIANA

* EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 345 PM UNTIL
1000 PM CDT.

* PRIMARY THREATS INCLUDE...
SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 2
INCHES IN DIAMETER POSSIBLE
SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70
STATUTE MILES EITHER SIDE OF A LINE FROM 10 MILES NORTH OF
SPRINGFIELD ILLINOIS TO 5 MILES SOUTHEAST OF BLOOMINGTON INDIANA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU8).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 507...

DISCUSSION...THUNDERSTORMS HAVE BEGUN INCREASING NEAR A WEAK SURFACE
LOW OVER NORTH CENTRAL ILLINOIS AND EAST-SOUTHEASTWARD ALONG A WEAK
WARM FRONT. CU FIELD IS ALSO INCREASING SOUTHWESTWARD FROM THE LOW
ALONG A WEAK COOL FRONT -- ALL WITHIN A VERY MOIST ENVIRONMENT WHERE
DAYTIME HEATING HAS YIELDED 2500 TO 3000 J/KG MIXED-LAYER CAPE.
SHEAR IS SUFFICIENT FOR MULTICELL/LINEAR ORGANIZATION -- AND PERHAPS
LOW-LEVEL ROTATION ALONG THE WARM FRONTAL ZONE WHERE SURFACE WINDS
ARE BACKED. THOUGH AN ISOLATED/BRIEF TORNADO WILL BE POSSIBLE NEAR
THIS BOUNDARY...LARGE HAIL AND LOCALLY DAMAGING WINDS WILL BE THE
MAIN SEVERE RISKS -- PARTICULARLY IF CONVECTION GROWS UPSCALE INTO
AN ORGANIZED/SOUTHWARD-MOVING CLUSTER AS CURRENTLY APPEARS POSSIBLE.

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 31030.


...GOSS

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