April 20: Severe Thunderstorm Watch #4

URGENT - IMMEDIATE BROADCAST REQUESTED
   SEVERE THUNDERSTORM WATCH NUMBER 171
   NWS STORM PREDICTION CENTER NORMAN OK
   225 PM CDT WED APR 20 2011
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
   
          SOUTHWEST AND CENTRAL TEXAS
   
   EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 225 PM UNTIL
   1000 PM CDT.
   
   HAIL TO 2.5 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 60
   STATUTE MILES NORTH AND SOUTH OF A LINE FROM 105 MILES SOUTHWEST
   OF SAN ANGELO TEXAS TO 110 MILES EAST NORTHEAST OF JUNCTION
   TEXAS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
   WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).
   
   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.
   
   OTHER WATCH INFORMATION...CONTINUE...WW 168...WW 169...WW 170...
   
   DISCUSSION...DEEPENING CUMULUS WILL EVENTUALLY GIVE WAY TO TSTM
   DEVELOPMENT ALONG LOW-LEVEL BAROCLINIC ZONE WHICH HAS BECOME
   QUASI-STATIONARY.  AMBIENT WARM SECTOR ENVIRONMENT IS CHARACTERIZED
   BY STEEP LAPSE RATES WITH MLCAPE OF 3000-4000+ J/KG.  GIVEN THE
   PRESENCE OF 30-35 KT EFFECTIVE BULK SHEAR...THE POTENTIAL WILL EXIST
   FOR ORGANIZED MULTICELL AND SOME SUPERCELL STRUCTURES CAPABLE OF
   LARGE HAIL AND LOCALLY DAMAGING WIND GUSTS.
   
   AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
   TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
   KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
   MOTION VECTOR 27025.