April 15: Tornado Watch #5

URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 144
   NWS STORM PREDICTION CENTER NORMAN OK
   240 PM CDT FRI APR 15 2011
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   TORNADO WATCH FOR PORTIONS OF 
   
          CENTRAL AND EASTERN LOUISIANA
          CENTRAL AND SOUTHERN MISSISSIPPI
          COASTAL WATERS
   
   EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 240 PM UNTIL
   1000 PM CDT.
   
   TORNADOES...HAIL TO 2 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 75 STATUTE
   MILES EAST AND WEST OF A LINE FROM 15 MILES NORTH NORTHEAST OF
   COLUMBUS MISSISSIPPI TO 15 MILES SOUTHEAST OF LAFAYETTE
   LOUISIANA.  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.
   
   OTHER WATCH INFORMATION...CONTINUE...WW 140...WW 141...WW
   142...WW 143...
   
   DISCUSSION...PRE-FRONTAL CLUSTER OF TORNADIC SUPERCELLS OVER
   PORTIONS OF CNTRL MS WILL PROGRESS EWD TOWARD THE AL BORDER WITH
   ADDITIONAL STORMS INTENSIFYING THIS AFTERNOON ALONG COLD
   FRONT/DRYLINE FROM WRN MS INTO CNTRL LA.  AMBIENT WARM SECTOR AIR
   MASS IS WARM AND QUITE MOIST WITH MLCAPE VALUES OF 1000-2000 J/KG. 
   THE STRONGEST LOW-LEVEL SHEAR AND RESULTANT GREATEST SIGNIFICANT
   TORNADO THREAT WILL EXIST FROM JUST E OF JAN TO MEI WHERE AMBIENT
   STREAMWISE VORTICITY IS BEING AUGMENTED BY A DIFFERENTIAL
   HEATING/OUTFLOW BOUNDARY.  ELSEWHERE THE COMBINATION OF EFFECTIVE
   BULK SHEAR OF 50-60 KT AND EFFECTIVE SRH OF 150-300 M2/S2 WILL BE
   SUPPORTIVE OF SUPERCELLS CAPABLE OF TORNADOES...LARGE HAIL AND
   DAMAGING WINDS.
   
   AVIATION...TORNADOES AND 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 26035.