MESOSCALE DISCUSSION 0123
   NWS STORM PREDICTION CENTER NORMAN OK
   0122 PM CST WED FEB 18 2009
   
   AREAS AFFECTED...PARTS OF S-CENTRAL LA AND SRN MS
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 181922Z - 182015Z
   
   SEVERE POTENTIAL WILL GRADUALLY INCREASE.  CONVECTIVE TRENDS WILL BE
   MONITORED AND A WW MAY BE NEEDED BY 21Z.
   
   AT 19Z...VISIBLE SATELLITE IMAGERY SHOWS GRADUALLY DEEPENING CU
   ALONG LOW LEVEL CONFLUENCE ZONE ORIENTED FROM NEAR 20 MI WSW POE TO
   45 MI WSW JAN.  RESIDUAL HIGH CIRRUS SHIELD HAS IMPEDED DIABATIC
   HEATING/DESTABILIZATION OVER AREAS FARTHER S AND E...BUT AREAS
   IMMEDIATELY ALONG AND NEAR CONFLUENCE ZONE HAVE CLEARED.  LATEST
   KLCH SINGLE SITE RADAR IMAGERY SHOWS DEVELOPING TSTMS OVER
   RAPIDES/AVOYELLES PARISHES IN LA AND LIBERTY COUNTY TX.  
   18Z LCH/JAN/LIX ALL SHOW STRONG NEARLY UNIDIRECTIONAL DEEP FLOW
   PROFILES /70 KTS AT 500MB/...WHICH WILL SUPPORT STORM ORGANIZATION
   AND THE POTENTIAL FOR SPLITTING SUPERCELLS ONCE SUSTAINED UPDRAFTS
   DEVELOP.  STRONGER LOW LEVEL SHEAR IS EXPECTED TO REMAIN CONFINED
   OVER MS/SERN LA /AOB 200 MS/S2 EFFECTIVE SRH/ BEFORE WEAKENING AS
   STRONGER BELT OF 850MB FLOW MOVES AWAY FROM REGION THIS EVENING. 
   THIS WILL COINCIDE WITH A GREATER POTENTIAL FOR AN ISOLD TORNADO
   THREAT THIS AFTERNOON OVER PARTS OF S-CENTRAL MS COMPARED TO AREAS W
   OVER SWRN LA.  NONETHELESS...EXPECTED SCTD TSTM COVERAGE WILL POSE A
   RISK FOR LARGE HAIL...DMGG WINDS...AND PERHAPS AN ISOLD TORNADO OR
   TWO.
   
   ..SMITH.. 02/18/2009
   
   
   ATTN...WFO...MOB...JAN...LIX...LCH...SHV...
   
   LAT...LON   30579356 30969303 32049070 32138924 31638830 31218837
               30708868 30229011 30109158 29879307 29969351 30169369
               30579356