SWODY2
SPC AC 250640
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CST SUN DEC 25 2011
VALID 261200Z - 271200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MID-UPPER CYCLONE CURRENTLY OVER SERN NM AND FAR W TX IS EXPECTED TO
PIVOT ERRATICALLY OVER SRN HIGH PLAINS THROUGH DAY-1...WHILE PHASING
WITH TRAILING VORTICITY LOBES NOW LOCATED FARTHER W AND SW ACROSS
AZ...BAJA..AND INTERIOR NWRN MEX. AS THIS OCCURS...MAIN CYCLONE
SHOULD CONSOLIDATE/STRENGTHEN...THEN BEGIN MOVING EWD EARLY
DAY-2...WITH 500-MB LOW CROSSING W-CENTRAL/N-CENTRAL TX AROUND
27/00Z. CYCLONE THEN SHOULD BEGIN TO MERGE WITH AREA OF NRN-STREAM
HEIGHT FALLS AND ACCELERATE ENEWD ACROSS ARKLATEX...REACHING ERN AR
BY END OF PERIOD.
AT SFC...FRONTAL-WAVE LOW NOW ANALYZED OVER NWRN GULF...OFFSHORE
LOWER-MIDDLE TX COAST...IS FCST TO SHIFT SLOWLY NEWD THROUGH DAY-1.
LOW THEN SHOULD EITHER MOVE OR RE-DEVELOP INLAND...REACHING
E-CENTRAL LA/SWRN MS AREA BY 27/00Z...WITH COLD FRONT SWD ACROSS
S-CENTRAL LA COAST INTO NWRN GULF. BY 27/12Z...SFC LOW SHOULD LIFT
NEWD ACROSS MS TO NWRN AL/MID TN REGION...WITH COLD FRONT SSEWD
ACROSS WRN PORTIONS FL PANHANDLE. EVEN MORE IMPORTANT BOUNDARY WILL
BE MARINE FRONT -- NOW ANALYZED EWD FROM LOW ACROSS N-CENTRAL GULF
THEN ESEWD TOWARD SRN FL. THIS FRONT...S OF WHICH SFC DEW POINTS
UPPER 60S TO LOW 70S F WILL BE COMMON...MAY MOVE SLIGHTLY INLAND
SERN LA AND BRUSH COASTAL AREAS OF MS/AL/FL PANHANDLE PRIOR TO COLD
FROPA.
...CENTRAL GULF COAST REGION...
TSTMS SHOULD DEVELOP IN AT LEAST THREE REGIMES EARLY IN PERIOD...IN
LIKELY ORDER OF OCCURRENCE...
1. ELEVATED WAA CONVEYOR INLAND OVER LA...N OF SFC LOW...AND FCST TO
MOVE NNEWD THROUGH WEAK INSTABILITY TOWARD OH VALLEY THROUGH
EVENING. THIS MAY BECOME BLENDED WITH NRN END OF NEXT TWO
PROCESSES...
2. EARLY-PERIOD THUNDER OVER SRN/ERN TX ATOP SFC COLD SECTOR...BUT
NEAR INVERTED SFC TROUGH EXTENDING NNWWD FROM GULF LOW. ASSOCIATED
WAA/MOISTURE TRANSPORT REGIME AHEAD OF EJECTING MID-UPPER LOW SHOULD
BOOST THETAE IN 850-700 MB LAYER JUST ENOUGH TO YIELD UP TO 500 J/KG
MUCAPE. THIS PLUME OF CONVECTION MAY REMAIN NW OF SFC FRONTAL ZONE
THROUGH MUCH OF PERIOD...BUT MAY CATCH UP DURING EVENING/OVERNIGHT
HOURS WITH...
3. BAND OF CONVERGENCE ACCOMPANYING SFC-900 MB COLD FRONT...WITH
PROBABLE QUASI-LINEAR CONVECTIVE MODE. TSTMS SHOULD BUILD SWD ALONG
FRONT INTO GULF...WITH EFFECTIVE LIFTED PARCELS ROOTED AT OR VERY
NEAR SFC GENERALLY ALONG AND S OF I-10. FCST LOW-LEVEL HODOGRAPHS
WILL BE LARGE WITH SELY WINDS NEAR MARINE FRONT...ESPECIALLY FROM
AFTER ABOUT 27/03Z ONWARD. HOWEVER...INSTABILITY WILL BE
LIMITED...EVEN WITH RICH LOW-LEVEL MOISTURE ALONG IMMEDIATE COASTAL
AREAS. MIDLEVEL LAPSE RATES AROUND 6 DEG C/KM SHOULD KEEP MLCAPE
BELOW 500 J/KG IN SFC WARM SECTOR...WHOSE INLAND EXTENT REMAINS
QUITE UNCERTAIN. ATTM SVR POTENTIAL APPEARS TOO CONDITIONAL/MRGL
FOR MORE THAN 5% RISK AREA.
..EDWARDS.. 12/25/2011
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