DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281238
SWODY1
SPC AC 281236

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0636 AM CST FRI DEC 28 2012

VALID 281300Z - 291200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
IN MID-UPPER LEVELS...MOISTURE CHANNEL IMAGERY INDICATED POSITIVELY
TILTED TROUGHING FROM MN SWWD ACROSS CENTRAL PLAINS TO NWRN
MEX...ANCHORED BY SMALL PERTURBATION OVER FSD REGION AND MORE
SUBSTANTIAL ONE FROM TX PANHANDLE ACROSS SERN NM AND FAR W TX. SRN
SHORTWAVE TROUGH IS EXPECTED TO MOVE ENEWD TO OZARKS...SERN OK AND
N-CENTRAL/W-CENTRAL TX BY 00Z...THEN ACCELERATE TO OH...ERN TN AND
EXTREME NRN AL BY END OF PERIOD.

AT SFC...WEAK FRONTAL-WAVE LOW ANALYZED AT 12Z OVER SE TX BETWEEN
HOU-BPT IS FCST TO MOVE ENEWD ACROSS CENTRAL LA DURING DAY...TO
E-CENTRAL/SERN MS BY 00Z...OCCLUDING OVERNIGHT BEFORE REACHING WV
AROUND 12Z. TRAILING SFC COLD FRONT SHOULD CROSS SERN LA AROUND
00Z...ERN AL AND WRN FL PANHANDLE IN 06Z-09Z TIME FRAME...AND
SC...SRN GA AND ERN FL PANHANDLE BY 12Z. TWO WARM FRONTAL ZONES
WERE ANALYZED --
1. OLDER/SYNOPTIC BOUNDARY EXTENDING SEWD FROM LOW OVER CENTRAL
GULF...WITH WEAK BAROCLINIC GRADIENT BUT STILL CHARACTERIZED BY
WELL-DEFINED ISODROSOTHERMAL CHANGE...AND
2. MARINE FRONT OVER BPT AREA EWD ACROSS MS RIVER MOUTH.
PRIND BOUNDARIES WILL MERGE FROM W-E...MOVING SLIGHTLY INLAND JUST
AHEAD OF SFC LOW SUCH THAT NARROW LOBE OF WARM SECTOR PENETRATES
INLAND FOR A FEW HOURS AT ANY GIVEN COASTAL LOCALE PRIOR TO COLD
FROPA.

...W GULF COASTAL PLAIN TO LOWER DELTA REGION...
BKN STRAND OF SHOWERS -- AND MORE RECENTLY ISOLATED TSTMS -- HAVE
BEEN INTENSIFYING GRADUALLY DURING PAST FEW HOURS...IN WELL-DEFINED
SFC CONFLUENCE AXIS LOCATED FROM LOW SSWWD ACROSS GULF WATERS. MRGL
POTENTIAL IS EVIDENT FOR BOTH DAMAGING GUSTS AND A TORNADO. REF SPC
MESOSCALE DISCUSSION 2244 FOR NEAR-TERM DETAILS.

OBSERVED CONVECTIVE TRENDS AND SHORT-RANGE/CONVECTION-RESOLVING
MODELS CONCUR WITH IDEA OF THIS FEATURE SHIFTING ENEWD ACROSS
SWRN/S-CENTRAL LA THROUGH REMAINDER MORNING...JUST AHEAD OF SFC COLD
FRONT. ACTIVITY SHOULD CONTINUE TO DEEPEN AND EVOLVE INTO PRIMARY
TSTM BAND ON BOTH SIDES OF WARM FRONT FROM SWRN LA SSWWD OVER GULF
AND NNEWD OVER LA...BEFORE PROCEEDING EWD ALONG GULF COAST TO FL
PANHANDLE. SRN PORTION NEAR COAST SHOULD BECOME SFC-BASED...AS
FOREGOING AIR MASS SLOWLY DESTABILIZES DUE TO LOW-LEVEL WAA...AND AT
LEAST MODEST SFC DIABATIC WARMING. SUPPORT ALOFT IS MORE
DOUBTFUL...HOWEVER. HEIGHT FALLS RELATED TO EJECTING W TX/NM TROUGH
BARELY WILL BRUSH SE TX/LA GULF COAST REGION...WITH MOST ROBUST
LARGE-SCALE FORCING FOR ASCENT REMAINING GENERALLY N OF I-20.

DEEP-LAYER SPEED SHEAR WILL BE FAVORABLE FOR SVR...AS HEIGHT
GRADIENT ALOFT ATTAINS MAXIMUM STRENGTH S OF PERTURBATION ALOFT.
HOWEVER...LACK OF STEEPER LAPSE RATES WILL LIMIT INLAND MLCAPE
250-750 J/KG IN MOST AREAS ALONG AND S OF I-10...FOR EXPECTED MID
60S SFC DEW POINTS ALONG AND S OF BLENDED MARINE/WARM FRONT.
GEOMETRY OF MID-UPPER TROUGH ALSO WILL COMPEL SUBSTANTIAL COMPONENT
OF MEAN FLOW PARALLEL TO CONVECTIVE/CONVERGENCE ZONE...SUPPORTING
PRIMARY QUASI-LINEAR STRUCTURE. WHILE ASSOCIATED BOW/LEWP
FORMATIONS AND RELATED LOCAL ENHANCEMENTS TO GUST/MESOVORTEX
POTENTIAL ARE POSSIBLE...SVR THREAT STILL APPEARS TOO CONDITIONAL
AND MRGL TO ASSIGN CATEGORICAL THRESHOLD PROBABILITIES ATTM.

..EDWARDS/JIRAK.. 12/28/2012

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