MESO: Mesoscale Discussion 2251

ACUS11 KWNS 121857
SWOMCD
SPC MCD 121856
MSZ000-LAZ000-ARZ000-122000-

MESOSCALE DISCUSSION 2251
NWS STORM PREDICTION CENTER NORMAN OK
0156 PM CDT WED OCT 12 2011

AREAS AFFECTED...NORTH CENTRAL-NERN LA INTO WEST CENTRAL-SWRN MS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 121856Z - 122000Z

TSTMS WILL CONTINUE TO INCREASE IN COVERAGE ACROSS NORTH
CENTRAL-NERN LA THIS AFTERNOON SPREADING EWD INTO WEST CENTRAL-SWRN
MS. AREAL COVERAGE OF ANY ATTENDANT SEVERE WEATHER THREAT IS
EXPECTED TO REMAIN LIMITED WHICH PRECLUDES THE NEED FOR A WW AT THIS
TIME. HOWEVER...IF ACTIVITY SHOWS SIGNS OF COLD POOL DEVELOPMENT/
INCREASED WIND THREAT...THEN A WW WOULD NEED TO BE CONSIDERED.

EARLY AFTERNOON OBJECTIVE ANALYSIS SHOWED THE AIR MASS ACROSS LA
INTO SWRN-WEST CENTRAL MS IS MARGINALLY-MODERATELY UNSTABLE /MLCAPE
500 TO AROUND 1000 J PER KG/. REGIONAL RADAR IMAGERY INDICATED AN
INCREASE IN TSTM DEVELOPMENT OVER NRN LA SINCE 1745Z...WITH THIS
ACTIVITY BEING AIDED BY FORCING FOR ASCENT ATTENDANT TO A SHORTWAVE
TROUGH MOVING EWD THROUGH THE LOWER MS VALLEY THIS AFTERNOON. IN
ADDITION...WEAK WAA IN THE 850-700 MB LAYER IS LIKELY AIDING IN THIS
DEVELOPMENT.

THE SOMEWHAT MARGINAL AVAILABLE INSTABILITY AND WEAKER DEEP LAYER
SHEAR OVER NRN LA TO WRN MS ARE TENDING TO RESULT IN WEAKER UPDRAFTS
WITH MINIMAL ORGANIZATION. ALTHOUGH STORMS WILL CONTINUE TO DEVELOP
AND SPREAD EWD INTO MS THIS AFTERNOON...THE MARGINAL CAPE/SHEAR
PARAMETER SPACE SUGGESTS THE SEVERE WEATHER THREAT WILL LIKELY BE
ISOLATED. MEANWHILE...A SURFACE RIDGE EXTENDING WWD FROM AL INTO MS
IS MAINTAINING A MORE STABLE AIR MASS AS EVIDENT BY THE EXTENSIVE
CLOUD SHIELD. THUS...EVEN IF STORMS COULD BECOME ORGANIZED OVER
NERN LA...THE SLOW DIMINISHING TREND IN THE WRN EXTENT OF THE CLOUD
SHIELD WILL LIKELY LIMIT THE AREAL COVERAGE FOR ANY SUBSTANTIAL
SEVERE WEATHER THREAT.

..PETERS.. 10/12/2011

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

ATTN...WFO...JAN...LIX...LCH...SHV...

LAT...LON 31329332 32329262 32979200 33189100 33089018 32198996
31069025 31029172 31089315 31329332

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