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WWUS20 KWNS 011756

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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 602

NWS STORM PREDICTION CENTER NORMAN OK

1245 PM CDT SAT SEP 1 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       CENTRAL ILLINOIS



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1245 PM UNTIL

900 PM CDT.



TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 60 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE

MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH NORTHWEST OF

PEORIA ILLINOIS TO 20 MILES WEST SOUTHWEST OF MATTOON ILLINOIS.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU2).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



DISCUSSION...SCTD...SHALLOW...NARROW CONVECTIVE CELLS HAVE

STRENGTHENED OVER CNTRL IL IN THE PAST 1-2 HRS. THIS ACTIVITY IS

FORMING IN CONVERGENT...NRN PART OF WARM SECTOR ASSOCIATED WITH

REMNANTS OF EX-HRCN ISAAC. AREA VWP DATA SUGGEST THAT LWR

TROPOSPHERIC  SHEAR IS NOT FAVORABLE FOR SUSTAINED LOW-LVL

MESOCYCLONES. HOWEVER...EVEN WITH MODEST SHEAR...PRESENCE OF

NUMEROUS DISCRETE UPDRAFTS IN MOISTURE-RICH LOW-LVL ENVIRONMENT HAS

PROVED FAVORABLE FOR AT LEAST BRIEF/WEAK

TORNADOES/FUNNELS...ESPECIALLY ALONG WSW-ENE STNRY FRONT ACROSS NRN

PART OF WW.



GIVEN THAT ENVIRONMENT IS NOT LIKELY TO MARKEDLY CHANGE IN THE NEXT

FEW HOURS...AND THAT LOW LVL BUOYANCY MAY BE BOOSTED BY ADDITIONAL

SFC HEATING...THE THREAT FOR BRIEF/WEAK TORNADOES MAY CONTINUE. AT

THE SAME TIME...A MORE SIGNIFICANT/LONGER-LASTING SVR THREAT MAY

EVOLVE IN SRN PART OF WW AS CONTINUED DESTABILIZATION OCCURS AHEAD

OF SHALLOW SQLN NOW IN W CNTRL/SW IL. AS THAT ACTIVITY STRENGTHENS

IT MAY YIELD DMGG WIND FROM SMALL BOWING SEGMENTS...IN ADDITION TO A

TORNADO OR TWO...LATER TODAY.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 50 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

450. MEAN STORM MOTION VECTOR 16030.





...CORFIDI

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