Post by SKYSUMMIT on Dec 5, 2013 10:35:37 GMT -6
MESOSCALE DISCUSSION 2057
NWS STORM PREDICTION CENTER NORMAN OK
1024 AM CST THU DEC 05 2013
AREAS AFFECTED...NERN LA / CNTRL MS / NWRN AL
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 051624Z - 051830Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...A CONDITIONAL THREAT FOR ISOLD DMGG WINDS AND A TORNADO OR
TWO APPEARS TO BE INCREASING ACROSS PORTIONS OF THE LOWER MS RIVER
VALLEY AND EVENTUALLY SPREADING NEWD INTO NWRN PORTIONS OF AL.
STORMS ARE EXPECTED TO DEVELOP/INCREASE IN INTENSITY DURING THE
17-22Z TIMEFRAME.
DISCUSSION...LATEST SUBJECTIVE SURFACE ANALYSIS SHOWS UPPER 60S TO
NEAR 70 DEG DEWPOINTS SPREADING NWD EITHER SIDE OF THE LA/MS BORDER
WITH UPPER 60S /AS OF 16Z/ ADVECTING NEWD INTO NERN MS AND NWRN AL.
VISIBLE SATELLITE IMAGERY DURING THE PAST FEW HOURS SHOWS THINNING
CLOUD COVER OVER CNTRL MS INTO W-CNTRL AL AS TEMPS RISE INTO THE
LOWER 70S AND THIS HEATING IS CONTRIBUTING TO FURTHER
DESTABILIZATION. OF PARTICULAR NOTE...THE 12Z RUN OF THE RAP MODEL
UNDER-FORECASTED SURFACE DEWPOINTS THIS MORNING /ROUGHLY 2 DEG F/
AND MAGNITUDE OF LOW-LEVEL SHEAR /COMPARED TO THE 12Z JAN RAOB/.
DESPITE SOMEWHAT MEAGER LAPSE RATES...MODIFYING THE 12Z JAN RAOB FOR
MID 70S TEMP/70 DEWPOINT BOOSTS MLCAPE TO AROUND 800 J/KG AND
REDUCES SBCINH WITHIN A VERY MOIST LOW LEVEL AIRMASS. MORE THAN
ADEQUATE SHEAR PROFILES ALONG WITH CONTINUED LOW-LEVEL CONFLUENT
REGIME AHEAD OF THE SEWD-MOVING COLD FRONT WILL LEND SUPPORT FOR
MAINLY DIURNALLY-PEAKING STORMS AND AN INCREASED PROPENSITY FOR
GRADUAL STORM INTENSIFICATION AND ISOLD LOW-LEVEL SUPERCELL
ROTATION--PERHAPS CAPABLE OF A DMGG WIND GUST OR TORNADO WITH THE
LONGER-LIVED CIRCULATIONS.
..SMITH/CORFIDI.. 12/05/2013
