SPC AC 031958

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0158 PM CST SAT JAN 03 2015

   VALID 032000Z - 041200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PORTIONS OF
   S-CNTRL/SERN/E-CNTRL MS AND FAR WRN AL...

   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH RISK ACROSS
   PORTIONS OF MS...AL...SRN LA...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
   ACROSS PORTIONS OF THE LOWER MS VALLEY TO MIDDLE TN AND THE CNTRL
   GULF COAST VICINITY...

   ...SUMMARY...
   SEVERE STORMS REMAIN POSSIBLE INTO EARLY TONIGHT FROM THE LOWER
   MISSISSIPPI VALLEY TO CENTRAL ALABAMA.

   ...DISCUSSION...
   LATEST OBSERVATIONAL DATA INDICATE THE GREATEST SHORT-TERM SVR-TSTM
   AND TORNADO POTENTIAL EVOLVING ALONG AND E OF A LINE FROM JUST N OF
   MCCOMB MS TO NEAR JACKSON MS AND TO NEAR STARKVILLE MS EWD ACROSS
   PORTIONS OF E-CNTRL AND SERN MS INTO ADJACENT FAR WRN AL. THIS IS
   WHERE AN UPGRADE TO ENHANCED DESIGNATION HAS BEEN INCLUDED TO
   ACCOUNT FOR A GREATER TORNADO POTENTIAL.

   LOW-LEVEL SLYS CONTINUE TO DRIVE THE NWD EXTENSION OF DEWPOINTS FROM
   64F TO 67F TO THE E OF A RAIN SHIELD EXTENDING FROM THE MID-SOUTH TO
   SWRN LA. NEAR-SFC ROOTED CONVECTION IS BECOMING APPARENT ALONG THE
   ERN FRINGES OF THIS RAIN SHIELD BETWEEN JACKSON AND VICKSBURG...WITH
   ADDITIONAL TSTMS DEVELOPING NNEWD WITHIN THE WARM SECTOR FROM
   S-CNTRL MS TO SWRN AL WHERE SFC PRESSURE FALLS OF 2.0-3.5 MB PER 2
   HOURS ARE HIGHLIGHTING STRENGTHENING FORCING FOR ASCENT IN THE WARM
   SECTOR. EMBEDDED CIRCULATIONS/SUPERCELLS ARE BECOMING APPARENT WITH
   THE LATTER ACTIVITY OVER S-CNTRL MS -- A MANIFESTATION OF AROUND 200
   M2/S2 OF 0-1-KM SRH SAMPLED BY THE 18Z JAN RAOB. CLOUD
   BREAKS/TRANSLUCENCE OUTSIDE OF WARM-SECTOR CONVECTION WILL CONTINUE
   TO PERMIT MODEST DIURNAL HEATING OF THIS MOIST AIR...ALLOWING THE
   CORRIDOR OF MARGINAL SFC-BASED INSTABILITY TO CONTINUE EXTENDING NWD
   ACROSS PORTIONS OF ERN MS AND WRN AL. LOW-LEVEL FLOW IS EXPECTED TO
   REMAIN SUFFICIENTLY STRONG -- SUPPORTING EFFECTIVE SRH FROM 200-300
   M2/S2 -- FOR MIXED-MODE SUPERCELL/QLCS ACTIVITY TO PRODUCE A GREATER
   TORNADO RISK AS IT TRACKS ACROSS PORTIONS OF E-CNTRL/SERN MS INTO
   FAR WRN AL THROUGH THE EVENING.

   OTHER CHANGES TO THE DAY-1 CONVECTIVE OUTLOOK INCLUDE THE FOLLOWING:

   /1/ THE NRN-EXTENT OF THE SLIGHT-RISK AREA HAS BEEN EXTENDED NWD
   ACROSS PORTIONS OF ERN MS AND NRN AL. RECENT SFC OBSERVATIONS
   INDICATE RICHER BOUNDARY-LAYER MOISTURE EXTENDING INTO THESE AREAS
   SUPPORTING MARGINAL INSTABILITY. QLCS SEGMENTS MAY OFFER SOME
   POTENTIAL FOR SVR WINDS AND PERHAPS A TORNADO IN THE STRONGLY
   SHEARED ENVIRONMENT INTO THIS EVENING.
   /2/ THE SRN EXTENT OF THE SLIGHT-RISK AREA HAS BEEN TRIMMED...
   ACROSS SRN LA...WHERE LOW-LEVEL FLOW IS BECOMING INCREASINGLY
   UNIDIRECTIONAL AND DEEP ASCENT IS LESSENING. THESE FACTORS WILL
   CONTINUE TO LOWER THE SVR-TSTM RISK.

   ..COHEN.. 01/03/2015

   .PREV DISCUSSION... /ISSUED 1002 AM CST SAT JAN 03 2015/

   ...SYNOPSIS...
   WATER VAPOR LOOPS CONTINUE TO SHOW A STRONG UPPER LOW OVER WEST
   TX...WITH MULTIPLE SHORTWAVE TROUGHS EMBEDDED IN THE FAST
   SOUTHWESTERLY MID LEVEL FLOW FROM NORTHERN MEXICO INTO THE TN
   VALLEY.  ONE SUBTLE FEATURE APPEARS TO HAVE CROSSED THE MEXICAN
   MOUNTAINS OVERNIGHT AND IS AIDING IN WEAK LIFT OVER THE WESTERN GULF
   OF MEXICO.  THIS FEATURE WILL TRACK NORTHEASTWARD TOWARD LA/MS/AL
   THIS AFTERNOON AND HELP TO POSE A RISK OF A FEW SEVERE STORMS. 

   ...SERN LA/SRN MS/WRN AL...
   00Z AND 12Z MODEL SOLUTIONS REMAIN CONSISTENT IN SHOWING
   THUNDERSTORM INTENSIFICATION OCCURRING OVER SOUTHEAST LA BY MID
   AFTERNOON.  STORMS THAT FORM IN THIS PRE-FRONTAL ENVIRONMENT WILL BE
   IN A REGION OF FAVORABLE DEEP LAYER AND LOW LEVEL VERTICAL SHEAR FOR
   SUPERCELL STRUCTURES. WEAK DAYTIME HEATING WILL ALSO OCCUR IN A
   CORRIDOR FROM SOUTHEAST LA...ACROSS SOUTHERN MS...INTO SOUTHWEST AL
   WITH MLCAPE VALUES OF 500-1000 J/KG.  LOCALLY DAMAGING WINDS AND A
   TORNADO OR TWO ARE POSSIBLE IN THIS REGION THROUGH THE EARLY
   EVENING.

   ...NRN MS/NRN AL/MIDDLE TN...
   FARTHER NORTH...INSTABILITY WILL BE QUITE WEAK OVER NORTHERN MS/AL
   INTO MIDDLE TN.  HOWEVER...VERY STRONG LOW LEVEL WINDS MAY BE
   SUFFICIENT FOR STRONG TO POTENTIALLY DAMAGING WINDS WITH CONVECTION
   THAT FORMS ALONG/AHEAD OF THE COLD FRONT THIS AFTERNOON AND EVENING.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z