MESOSCALE DISCUSSION 2517
NWS STORM PREDICTION CENTER NORMAN OK
0320 PM CST WED DEC 24 2008
AREAS AFFECTED…SE LA…SRN MS…SW AL
CONCERNING…SEVERE POTENTIAL…WATCH UNLIKELY
VALID 242120Z – 242245Z
A MARGINAL SEVERE THREAT SHOULD CONTINUE LATE THIS AFTERNOON ACROSS
SE LA…SRN MS AND SW AL. A MARGINAL TORNADO THREAT AND POTENTIAL
FOR STRONG GUSTY WINDS MAY EXIST WITH THE MORE INTENSE CELLS.
HOWEVER…THE THREAT SHOULD REMAIN TOO ISOLATED TO WARRANT THE
ISSUANCE OF A WEATHER WATCH.
LATEST WATER VAPOR IMAGERY SHOWS A PLUME OF MID-LEVEL MOISTURE
EXTENDING FROM THE WRN GULF OF MEXICO NEWD INTO SRN MS AND SCNTRL
AL. CONVECTION IS INCREASING IN THE MOIST PLUME AND THIS LIKELY IS
IN RESPONSE TO SFC HEATING AND MAY BE AIDED BY THE PRESENCE OF A
VERY SUBTLE SHORTWAVE FEATURE. RUC ANALYSIS OVER SE LA AND SRN MS
SUGGESTS INSTABILITY HAS INCREASED WITH SBCAPE VALUES CURRENTLY
RANGING FROM 1000 TO 1500 J/KG. IN ADDITION…THE MOBILE AND
BIRMINGHAM WSR-88D VWPS HAVE MODERATE VERTICAL SHEAR PROFILES
SUGGESTING THE SHEAR MAY SUPPORT A FEW ROTATING STORMS. THE STRONGER
LOW-LEVEL SHEAR IS LOCATED ACROSS SW AND CNTRL AL WHERE 0-3 KM SRH
IS ESTIMATED TO BE 300 TO 350 M2/S2 ACCORDING THE WSR-88D VWPS WHERE
A MARGINAL TORNADO THREAT MAY EXIST LATE THIS AFTERNOON. FURTHER
SOUTHWEST ACROSS SRN MS…GREATER INSTABILITY AND STEEPER LOW-LEVEL
LAPSE RATES MAY FAVOR STRONG WIND GUSTS.
..BROYLES.. 12/24/2008
