MESO: Mesoscale Discussion 2125

ACUS11 KWNS 270044
SWOMCD
SPC MCD 270044
MSZ000-LAZ000-ARZ000-TXZ000-270215-

MESOSCALE DISCUSSION 2125
NWS STORM PREDICTION CENTER NORMAN OK
0644 PM CST MON NOV 26 2012

AREAS AFFECTED...ERN TX...NRN/CNTRL/WRN LA...FAR SRN
AR...SWRN/W-CNTRL MS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 270044Z - 270215Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...CONVECTIVE DEVELOPMENT IS UNDERWAY ACROSS PARTS OF NERN TX
AND NWRN LA...AND THE ISSUANCE OF A SVR TSTM WATCH IS POSSIBLE.

DISCUSSION...OBSERVED SOUNDINGS FROM SHREVEPORT INDICATE COOLING
WITHIN THE 730-600-MB LAYER FROM 18Z TO 00Z...POTENTIALLY INDICATING
THE INCREASE IN LARGE-SCALE ASCENT DOWNSTREAM OF A MID-LEVEL VORT
MAX SOON TO EMERGE OVER CNTRL/SRN TX. THE ASCENT/COOLING HAS
CONTRIBUTED TO DESTABILIZATION...WITH THE 00Z SHREVEPORT RAOB
INDICATING AROUND 1100 J/KG OF MLCAPE WITH AROUND 20 J/KG MLCIN.
RADAR RETURNS HAVE BEEN NOTED FROM RUSK COUNTY TX TO BOSSIER PARISH
LA...WHICH IS THE MANIFESTATION OF ONGOING CONVECTIVE INITIATION AS
A COLD FRONT APPROACHES FROM THE NW...WITH MESOSCALE ASCENT ENHANCED
BY CONVERGENCE AROUND A WEAK SUB-SYNOPTIC-SCALE CYCLONE POSITIONED
NEAR SHREVEPORT. STORMS WILL LIKELY INCREASE IN NUMBER AND INTENSITY
DURING THE NEXT HOUR OR TWO...POTENTIALLY EVOLVING INTO ONE OR MORE
SQUALL LINES NEAR/JUST AHEAD OF THE FRONT AMIDST 20-35 KT OF
EFFECTIVE BULK SHEAR. SVR WINDS/HAIL WILL BE THE MAIN CONCERN WITH
THIS ACTIVITY...MAINLY TO THE W OF A NNW/SSE-ORIENTED CONFLUENCE
AXIS/WARM FRONT ACROSS THE WRN HALF OF LA. WEAKER INSTABILITY
FARTHER E TOWARD THE MS RIVER INTO WRN MS AND N INTO FAR SRN AR MAY
MITIGATE THE THREAT WITH TIME...WHERE WW ISSUANCE IS RELATIVELY LESS
LIKELY.

..COHEN/DARROW.. 11/27/2012

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

ATTN...WFO...JAN...LIX...LZK...LCH...SHV...HGX...

LAT...LON 29849303 29549484 30929543 32149468 33189347 33289272
33159198 32819123 31989096 31139139 30359203 29849303

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