MESOSCALE DISCUSSION 0069
   NWS STORM PREDICTION CENTER NORMAN OK
   1200 PM CST TUE FEB 01 2011
   
   AREAS AFFECTED...SRN-ERN LA/SWRN...WEST CENTRAL TO CENTRAL MS
   
   CONCERNING...TORNADO WATCH 9...
   
   VALID 011800Z - 011900Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 9 CONTINUES.
   
   AREAS E OF WW 9 OVER SERN MS  AND SWRN AL WILL NEED TO BE MONITORED
   FOR A NEW WATCH AS THE AIR MASS CONTINUES TO SLOWLY DESTABILIZE.
   
   THREAT FOR DAMAGING WINDS AND A FEW TORNADOES CONTINUES ACROSS
   ERN...SRN AND SERN LA INTO SWRN MS.  CURRENT TRENDS IN RADAR IMAGERY
   SHOWED THE NRN EXTENT OF THE STORMS...NOW ENTERING SWRN MS...WILL
   EXIT THE NERN PART OF WW 9 BY 20Z...WHILE THE SRN EXTENT SHOULD
   REACH THE SERN PART OF THIS WATCH AROUND 21Z.  MEANWHILE...SEVERE
   WEATHER THREAT WILL CONTINUE TO END WITH THE PASSAGE OF THE SQUALL
   LINE...SUCH THAT PARISHES AND COUNTIES CAN BE REMOVED FROM WW 9 WEST
   OF THIS LINE.  
   
   AT 17Z...PRIMARY CYCLONE WAS LOCATED OVER E CENTRAL AR...WITH TRENDS
   IN MID-LATE MORNING SURFACE ANALYSES SHOWED PRESSURE FALLS FROM AR
   INTO SERN MO AND MID SOUTH SUPPORTING A CONTINUED ENE TRACK OF THIS
   FEATURE.  MEANWHILE...TWO CORRIDORS OF SURFACE PRESSURE RISES
   EXTENDED SWD AND SWWD FROM THE LOW WITH THE LEADING ONE LOCATED
   IMMEDIATELY IN THE WAKE OF THE SQUALL LINE...WHILE THE SECOND
   PRESSURE RISE AREA ACROSS E TX MARKS THE LEADING EDGE OF THE COLDER
   AIR WITH THE ARCTIC FRONT.  AT 1730Z...REGIONAL RADAR IMAGERY SHOWED
   THE SQUALL LINE/LEAD WIND SHIFT EXTENDING SSWWD FROM VICINITY OF HEZ
   TO SOUTH CENTRAL LA...WITH THIS LINE TRACKING EWD AT 35 KT AND
   EMBEDDED CELLS MOVING ENE UP TO 50 KT.  A WARM FRONT EXTENDED FROM
   VICINITY OF BTR ESEWD TO OFF THE MS GULF COAST AND 50-60 MILES S OF
   THE FL PANHANDLE.  LOW LEVEL WAA ALONG THE WARM FRONT WILL CONTINUE
   TO SUPPORT TSTM DEVELOPMENT AHEAD OF THE PRIMARY SQUALL LINE...WITH
   STRONG LOW LEVEL SHEAR /EFFECTIVE SRH 300-700 M2 PER S2/ INVOF OF
   THE WARM FRONT SUGGESTING A THREAT FOR ENHANCED LOW LEVEL ROTATION. 
   MODIFIED 15Z SLIDELL SPECIAL SOUNDING FOR CURRENT SURFACE CONDITIONS
   INDICATED AN UNCAPPED ENVIRONMENT WITH MLCAPE CLOSE TO 400 J/KG AND
   AN INCREASE IN LOW LEVEL HODOGRAPH CURVATURE SINCE 12Z.
   
   50+ KT SLY LLJ EXTENDING INTO THE LOWER MS VALLEY/ADJACENT GULF
   COAST STATES WILL MAINTAIN AN INFLUX OF MOISTURE...WITH SURFACE
   DEWPOINTS IN THE LOWER-MID 60S ACROSS SERN LA AND FAR SRN MS
   SPREADING INTO SWRN AL THIS AFTERNOON.  DESPITE LIMITED DIABATIC
   HEATING...THIS MOISTURE AND MIDLEVEL LAPSE RATES /6.5-7.0 C PER KM/
   WILL CONTINUE TO SUPPORT MARGINAL INSTABILITY /MLCAPE AOB 500 J PER
   KG/.  THESE FACTORS COMBINED WITH BULK SHEAR IN EXCESS OF 50+ KT
   WILL MAINTAIN SUPPORT FOR ORGANIZED STORMS/A FEW SUPERCELLS AS
   ACTIVITY ADVANCES EWD THIS AFTERNOON.
   
   ..PETERS.. 02/01/2011
   
   
   ATTN...WFO...MOB...JAN...LIX...LCH...
   
   LAT...LON   29139268 31019180 32579119 32838973 32178907 31668798
               31458700 30028702 29608814 28898865 28618914 28769127
               29149195 29139268