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WWUS20 KWNS 131154

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SPC WW 131154

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 165

NWS STORM PREDICTION CENTER NORMAN OK

655 AM CDT THU MAY 13 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND NORTHEAST ILLINOIS

       EXTREME NORTHWEST INDIANA



EFFECTIVE THIS THURSDAY MORNING FROM 655 AM UNTIL 1100 AM CDT.



HAIL TO 1 INCH 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 40

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 20 MILES NORTHWEST

OF SPRINGFIELD ILLINOIS TO 30 MILES SOUTH OF VALPARAISO INDIANA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU5).



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 164...



DISCUSSION...A SMALL BOWING SEGMENT IS DEVELOPING AND MOVE RAPIDLY

NEWD ALONG AN OUTFLOW BOUNDARY FROM EARLIER CONVECTION ACROSS NE IL.

 ADDITIONALLY...THE SURFACE WARM FRONT IS MOVING NWD ACROSS CENTRAL

IL...AND WILL LIKELY MERGE WITH THE OUTFLOW BOUNDARY.  THIS WILL

PROVIDE A FOCUSED CORRIDOR TO MAINTAIN THE CONVECTIVE CLUSTER FOR A

FEW HOURS...AND THE CONVECTION WILL BE ROOTED AT OR VERY NEAR THE

GROUND.  GIVEN THE FAST STORM MOTION AND LOW-MIDLEVEL FLOW IN EXCESS

OF 50 KT...THERE WILL SOME POTENTIAL FOR DAMAGING WINDS TO REACH THE

GROUND.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM MOTION

VECTOR 25050.





...THOMPSON

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