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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 154

NWS STORM PREDICTION CENTER NORMAN OK

105 PM CDT TUE APR 19 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       CENTRAL ILLINOIS

       CENTRAL AND SOUTHERN MISSOURI



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 105 PM UNTIL

900 PM CDT.



TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 100 STATUTE

MILES EAST AND WEST OF A LINE FROM 55 MILES SOUTH SOUTHEAST OF

SPRINGFIELD MISSOURI TO 65 MILES NORTH NORTHEAST OF ALTON

ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).



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...SURFACE LOW NEAR COU WILL DEVELOP NEWD INTO CNTRL IL BY

20/00Z WITH AN ASSOCIATED NWD RETREAT OF WARM FRONT TO VICINITY OF

THE I-70 CORRIDOR LATER TODAY.  TSTM DEVELOPMENT IS EXPECTED TO

OCCUR ON BOTH THE TRAILING COLD FRONT OVER W-CNTRL/SWRN MO AS WELL

AS ALONG RETREATING WARM FRONT AS REMAINING CAP IS REMOVED.  GIVEN

THE PRESENCE OF A MODERATELY TO STRONGLY UNSTABLE WARM SECTOR IN

PLACE WITH MLCAPE VALUES OF 2500-4000 J/KG AND EFFECTIVE BULK SHEAR

MAGNITUDES OF 40-50 KT...ENVIRONMENT WILL BE QUITE SUPPORTIVE OF

SUPERCELLS CAPABLE OF VERY LARGE HAIL...TORNADOES AND DAMAGING

WINDS.  THE GREATEST THREAT FOR TORNADOES WILL LIKELY RESIDE FROM

THE VICINITY OF THE SURFACE LOW EWD ALONG THE WARM FRONT WHERE

LOW-LEVEL SHEAR WILL REMAIN MAXIMIZED.



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

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 24035.





...MEAD

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