MESO: Mesoscale Discussion 0158

ACUS11 KWNS 122136
SWOMCD
SPC MCD 122135
FLZ000-ALZ000-MSZ000-LAZ000-122300-

MESOSCALE DISCUSSION 0158
NWS STORM PREDICTION CENTER NORMAN OK
0335 PM CST TUE FEB 12 2013

AREAS AFFECTED...S-CNTRL/ERN LA THROUGH SERN MS INTO SWRN AL AND THE
WRN FL PNHDL

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 122135Z - 122300Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...THE THREAT FOR SUPERCELLS CAPABLE OF TORNADOES WILL
INCREASE LATE THIS AFTERNOON INTO EVENING AND A TORNADO WATCH WILL
LIKELY BE REQUIRED PRIOR TO 00Z.

DISCUSSION...21Z SURFACE ANALYSIS SHOWED A SURFACE LOW SW OF HEZ
WITH AN ASSOCIATED WARM FRONT EXTENDING SEWD TO NEAR BTR/MSY AND
THEN EWD ACROSS THE SHELF WATERS S OF MOB BEFORE CURVING ENEWD ONTO
THE FL PNHDL /N OF AAF/. A COLD FRONT TRAILED THE SURFACE LOW SWD
TO E OF LCH. OVER THE PAST HOUR...TSTMS HAVE GENERALLY DIMINISHED
IN AREAL COVERAGE ACROSS THE DISCUSSION AREA...PERHAPS IN RESPONSE
TO THE PASSAGE OF A LEAD SHORT-WAVE TROUGH TO THE N OF THE REGION.
THIS HAS RESULTED IN THE MOST WIDESPREAD TSTMS DEVELOPMENT BECOMING
FOCUSED WELL TO THE N OF THE SURFACE WARM FRONT OVER CNTRL PARTS OF
MS AND AL. MOREOVER...RAPID-REFRESH AND 18Z NAM-DERIVED SOUNDINGS
INDICATE A WARM NOSE IN THE 700-550-MB LAYER WHICH MAY BE
PROHIBITING MORE ROBUST UPDRAFT GROWTH WITHIN THE WARM SECTOR.

IT STILL APPEARS PROBABLE THAT RENEWED HEIGHT FALLS AHEAD OF THE
PRIMARY MIDLEVEL TROUGH OVER THE SRN PLAINS IN CONJUNCTION WITH
LOW-LEVEL UPLIFT ALONG THE WARM AND COLD FRONTS WILL FOSTER AT LEAST
WIDELY SCATTERED TSTM DEVELOPMENT BY 00Z FROM S-CNTRL LA EWD INTO
FAR SRN PARTS OF MS/AL AND THE FL PNHDL. GIVEN THE PRESENCE OF A
MOIST AND AT LEAST MARGINALLY UNSTABLE WARM SECTOR AIR MASS AND
MODERATELY STRONG LOW-LEVEL AND DEEP-LAYER SHEAR...THE POTENTIAL
WILL EXIST FOR SUPERCELLS CAPABLE OF A FEW TORNADOES AND LOCALLY
DAMAGING WINDS.

..MEAD.. 02/12/2013

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...TAE...MOB...JAN...LIX...LCH...

LAT...LON 30009129 30829128 31388988 31568741 31408653 30438626
29878678 29568779 29499000 29579109 30009129

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