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WWUS20 KWNS 151700

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ILZ000-INZ000-MIZ000-OHZ000-160200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 479

NWS STORM PREDICTION CENTER NORMAN OK

1200 PM CDT THU JUL 15 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PART OF CENTRAL AND EASTERN ILLINOIS

       NORTHERN AND CENTRAL INDIANA

       PART OF SOUTHERN LOWER MICHIGAN

       FAR NORTHWEST OHIO



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM NOON UNTIL 900

PM CDT.



HAIL TO 2 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 100

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES EAST

NORTHEAST OF VALPARAISO INDIANA TO 40 MILES SOUTH SOUTHEAST OF

CHAMPAIGN ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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...TSTMS SHOULD CONTINUE TO INCREASE IN COVERAGE AND

INTENSITY THIS AFTERNOON ALONG PRE-FRONTAL WIND SHIFT AS WELL AS

ALONG SYNOPTIC COLD FRONT PUSHING THROUGH THE REGION.  THE AMBIENT

AIR MASS IS HOT AND VERY MOIST WITH MLCAPE LIKELY APPROACHING

3000-4000 J/KG LATER TODAY.  VERTICAL SHEAR IS NOT PARTICULARLY

STRONG...BUT THE PRESENCE OF DEEP WLY FLOW WILL BE SUPPORTIVE OF

ORGANIZED MULTICELL CLUSTERS AND LINE SEGMENTS...ESPECIALLY GIVEN

THE DEGREE OF INSTABILITY.  SOME HAIL WILL BE POSSIBLE...BUT

DAMAGING WIND GUSTS APPEAR TO BE THE PRIMARY THREAT.



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 28025.





...MEAD

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