April 19: Tornado Watch #1

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.