April 20: Severe Thunderstorm Watch #1

URGENT - IMMEDIATE BROADCAST REQUESTED
   SEVERE THUNDERSTORM WATCH NUMBER 168
   NWS STORM PREDICTION CENTER NORMAN OK
   105 PM CDT WED APR 20 2011
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
   
          FAR SOUTHEAST ARKANSAS
          NORTHEAST LOUISIANA
          MISSISSIPPI
   
   EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 105 PM UNTIL
   800 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 70
   STATUTE MILES NORTH AND SOUTH OF A LINE FROM 45 MILES SOUTH OF
   COLUMBUS MISSISSIPPI TO 60 MILES SOUTH OF MONTICELLO ARKANSAS. 
   FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
   OUTLINE UPDATE (WOUS64 KWNS WOU8).
   
   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 WILL INCREASE IN COVERAGE AND INTENSITY THIS
   AFTERNOON ALONG SYNOPTIC COLD FRONT AND PRECEDING CONVECTIVE OUTFLOW
   BOUNDARIES.  MODIFICATION OF 12Z JAN SOUNDING FOR CURRENT WARM
   SECTOR CONDITIONS SUGGESTS THAT ENVIRONMENT IS ALREADY STRONGLY
   UNSTABLE WITH MLCAPE OF AROUND 3000 J/KG.  WHEN COUPLED WITH THE
   STEEP MIDLEVEL LAPSE RATES AND 30-40 KT OF DEEP WLY
   SHEAR...ENVIRONMENT WILL BE SUPPORTIVE OF SUPERCELL AND ORGANIZED
   MULTICELLS CAPABLE OF LARGE HAIL AND DAMAGING WIND GUSTS.
   
   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 27030.