SWOMCD
SPC MCD 151039
MSZ000-LAZ000-ARZ000-TXZ000-151315-
MESOSCALE DISCUSSION 2110
NWS STORM PREDICTION CENTER NORMAN OK
0539 AM CDT THU OCT 15 2009
AREAS AFFECTED...PORTIONS SWRN AR...EXTREME NE TX...NRN LA...EXTREME
W-CENTRAL MS.
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 151039Z - 151315Z
CONDITIONS HAVE BECOME SOMEWHAT MORE FAVORABLE FOR ORGANIZED SVR
THREAT IN CORRIDOR EXTENDING SEWD FROM PRESENT/LOOSELY-ORGANIZED
CONVECTIVE COMPLEX OVER ARKLATEX REGION. POTENTIAL EXISTS FOR THIS
ACTIVITY TO GROW UPSCALE AND EVOLVE INTO MORE CONCENTRATED
MCS...INCREASING DAMAGING WIND THREAT AS IT MOVES SEWD.
MODIFIED RAOBS AND RUC SOUNDINGS INDICATE AVAILABLE/EFFECTIVE INFLOW
LAYER WILL REMAIN CHARACTERIZED BY VERY MOIST/HIGH-THETAE CONDITIONS
WITH RESULTANT BOOST IN AVAILABLE BUOYANCY IN SYSTEM RELATIVE SENSE.
SFC DEW POINTS GENERALLY LOW-MID 70S F IN FOREGOING AIR MASS WILL
OFFSET WEAK LAPSE RATES ALOFT ENOUGH TO SUPPORT 1000-200 J/KG MLCAPE
THROUGH ABOUT 13-14Z...INCREASING THEREAFTER WITH DIURNAL HEATING.
MEANWHILE...MLCINH IS ALREADY WEAK AND SHOULD NOT CHANGE APPRECIABLY
FOR ANOTHER 2-3 HOURS...GIVEN CONSTRAINTS IMPOSED BY MOISTURE ON
DIABATIC COOLING. OFFSETTING FACTORS WILL INCLUDE LITTLE OR NO
APPRECIABLE EVAPORATE COOLING EFFECTS ON STORM-SCALE TO ACCELERATE
DOWNDRAFTS GENERATED ALOFT...AND LACK OF STRONGER FLOW JUST ABOVE
SFC FOR SUSTAINED/BROAD ZONE OF DOWNWARD MOMENTUM TRANSFER.
DAMAGING WIND THREAT THEREFORE IS TIED MORE TO SMALLER SCALE
BOW/LEWP PROCESSES AND RELATED/LOCALIZED OUTFLOW SURGES. MCS SHOULD
CONTINUE TO MOVE GENERALLY PARALLEL TO AND INVOF
DIFFUSE/QUASISTATIONARY SFC FRONTAL ZONE. ALTHOUGH SFC WINDS WILL
REMAIN WEAK...EFFECTIVE SHEAR 40-50 KT WILL AIR POTENTIAL STORM
ORGANIZATION. TAIL END OF MCS...ESPECIALLY WITH ANY
PROPAGATIONAL/BACKBUILDING COMPONENT OF MOVEMENT...WILL REMAIN ON
NERN EDGE OF FAVORABLE LOW LEVEL HODOGRAPH STRUCTURES.
THEREFORE...WHILE ADDITIONAL SUPERCELLS ARE POSSIBLE AND TORNADO
RISK IS NON-ZERO...MAIN CONCERN WILL BE EPISODIC STG-SVR GUSTS.
..EDWARDS.. 10/15/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...JAN...LZK...SHV...
LAT...LON 33859445 33909272 33549172 32899085 32149070 31589192
32119352 33209440 33859445
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