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.
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