DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 141250
SWODY1
SPC AC 141248

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0648 AM CST FRI DEC 14 2012

VALID 141300Z - 151200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MAIN UPPER-AIR FEATURE FOR THIS FCST IS STG SHORTWAVE TROUGH AND
EMBEDDED MESO-ALPHA SCALE CIRCULATION...NOW EVIDENT IN MOISTURE
CHANNEL IMAGERY OVER NRN BAJA/NWRN GULF OF CA REGION. UPSTREAM
PERTURBATION OF EVEN SHORTER WAVELENGTH IS LOCATED OVER COASTAL PAC
NW THIS MORNING...SRN PORTION OF WHICH WILL MOVE SEWD AND AMPLIFY
ACROSS CENTRAL/SRN CA AND INTO MEAN TROUGH POSITION OVER AZ BY END
OF PERIOD. AS THIS OCCURS...LEADING/BAJA FEATURE WILL EJECT
NEWD...REACHING FROM ERN CO SWD ACROSS SRN HIGH PLAINS NEAR TX/NM
BORDER BY 00Z...AND LOWER MO RIVER VALLEY BY 15/12Z.

AT SFC...CYCLONE IS FCST TO SHIFT EWD OUT OF CENTRAL ROCKIES AROUND
00Z...REACHING HLC AREA BY 06Z THEN ERN NEB BY 12Z. RELATED
LOW-LEVEL WAA...MOIST ADVECTION AND MOISTURE TRANSPORT WILL BOOST
SFC THETAE BETWEEN SRN KS AND WRN GULF COAST. THIS
PROCESS...COMBINED WITH DIURNAL HEATING/MIXING OF HIGHER TERRAIN
OVER SRN HIGH PLAINS...SHOULD RESULT IN GRADUALLY SHARPENING DRYLINE
THROUGHOUT TODAY FROM TX PANHANDLE SWD INTO NRN COAHUILA. THIS
DRYLINE SHOULD MOVE OFF CAPROCK BY LATE AFTERNOON...SHORTLY BEFORE
BEING OVERTAKEN BY PAC COLD FRONT MOVING EWD OUT OF NM AND AHEAD OF
MID-UPPER TROUGH. COMBINED BOUNDARY SHOULD MOVE EWD TO NEAR
DRT...FTW...CHK...GBD LINE BY 06Z. BY 12Z...FRONT SHOULD REACH ERN
PORTIONS KS/OK AND S-CENTRAL TX.

...SOUTHERN PLAINS...
SCATTERED TO LOCALLY NUMEROUS TSTMS SHOULD DEVELOP THIS AFTERNOON IN
LINE OR ARC AND MOVE ENEWD...POSING THREAT FOR STG/ISOLATED SVR
GUSTS INTO EARLY EVENING OVER TX PANHANDLE/NW TX/WRN OK REGION...AND
ISOLATED SVR HAIL INTO TONIGHT ACROSS MORE OF WRN/CENTRAL OK AND NW
TX. EVEN SUB-SVR CONVECTIVE CONTRIBUTION TO STG/AMBIENT GRADIENT
FLOW MAY YIELD DAMAGING GUSTS. BRIEF TORNADO CANNOT BE RULED
OUT...BUT THREAT APPEARS VERY CONDITIONAL/MRGL ATTM.

POTENT DCVA AND LARGE-SCALE ASCENT IMMEDIATELY PRECEDING MID-UPPER
TROUGH HAS BEEN CONTRIBUTING TO CONVECTIVE PRECIP ALL NIGHT OVER
PORTIONS SRN/ERN AZ INTO WRN NM...WITH INTERMITTENT/EMBEDDED TSTMS.
RELATED SWATH OF STG SYNOPTIC FORCING/COOLING ALOFT WILL OFFSET
WEAKNESS OF LOW-LEVEL THETAE JUST ENOUGH FOR SOME CONCERN OF
SFC-BASED EFFECTIVE INFLOW PARCELS. FOR EXAMPLE...A FEW MODEL
SOUNDINGS MODIFIED FOR SFC TEMPS MID-UPPER 60S F DO YIELD
NARROW/TRANSIENT/PRECONVECTIVE CORRIDOR OF 300-800 J/KG MLCAPE...AND
CINH WEAK ENOUGH THAT TSTM UPDRAFTS MAY HAVE SOME ACCESS TO BOUNDARY
LAYER THROUGH FORCED ASCENT. HOWEVER...THIS REPRESENTS MOST
AGGRESSIVELY DESTABILIZED SOLUTION. EXPECT VERY STG VERTICAL
SHEAR...BY ALL MEASURES...ATOP DRYLINE/FRONT DURING 21Z-00Z TIME
FRAME. EVEN WITH RELATIVELY SHALLOW BUOYANT LAYERS...50-60 KT
EFFECTIVE SHEAR MAGNITUDES APPEAR PROBABLE.

HOWEVER...SEVERAL FACTORS WILL SUBSTANTIALLY LIMIT AVAILABLE
MOISTURE/INSTABILITY...AND BY EXTENSION...MAGNITUDE/ORGANIZATION OF
SVR THREAT. SFC DEW POINTS ARE ANALYZED ONLY IN LOW-MID 60S OVER
NWRN GULF AND DEEP S TX...WITH MID-50S STILL CONFINED TO S OF I-10.
THIS REVEALS INCOMPLETENESS OF MARINE AIRMASS MODIFICATION OF
TRAJECTORIES LEADING INTO NW TX...TX PANHANDLE AND WRN OK THIS
AFTERNOON AND EVENING. PRECIP IS FALLING INTO THIS AIR MASS ALREADY
ACROSS MOST OF LOWER-MIDDLE RIO GRANDE VALLEY...AND RELATED
CLOUDS/RAIN WILL COVER PROGRESSIVELY MORE OF SRN/CENTRAL TX
THROUGHOUT FORENOON HOURS. THIS WILL PRECLUDE ROBUST
MOISTURE/THETAE RETURN INTO MAIN CONVECTIVE REGIME...THOUGH STRENGTH
OF DEEP-LAYER ASCENT STILL SHOULD YIELD STRONGLY FORCED BAND/QLCS.
TSTM WIND POTENTIAL WILL DIMINISH WITH TIME THIS EVENING AS ACTIVITY
MOVES INTO INFLOW AIR MASS THAT IS PROGRESSIVELY LESS BUOYANT AND
MORE ELEVATED WITH EWD EXTENT.

..EDWARDS/SMITH.. 12/14/2012

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