SWODY2
SPC AC 220555
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 PM CST WED JAN 21 2009
VALID 231200Z - 241200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
IN MID-UPPER LEVELS...SPLIT FLOW PATTERN OVER NERN PACIFIC WILL
CONTRIBUTE TO PROGRESSIVE SRN STREAM ACROSS SWRN/S-CENTRAL CONUS
THIS PERIOD. MAIN FEATURE IN THAT FLOW BELT WILL BE SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OFFSHORE SRN CA
AND BAJA NEAR 120W. THIS PERTURBATION WILL DEAMPLIFY AS IT
ACCELERATES EWD OVER BAJA...NRN GULF OF CA...SRN CA AND AZ
DAY-1...WHILE UPSTREAM LOW PIVOTS SEWD/EWD OVER PACIFIC. LEADING
TROUGH THEN WILL MOVE ESEWD ACROSS NRN MEX...ELP-AREA BORDERLANDS
AND SWRN/CENTRAL TX THIS PERIOD...REACHING NEAR LOWER-MIDDLE TX
COAST BY 24/12Z.
MEANWHILE...NRN STREAM SHORTWAVE TROUGH -- NOW ANALYZED OVER
PORTIONS CENTRAL BC AND NRN AB -- IS FCST TO MOVE SEWD THEN EWD
ACROSS NRN PLAINS...NRN ONT AND UPPER GREAT LAKES THROUGH
DAY-2...CONTRIBUTING TO BROAD/CYCLONIC FLOW BELT FROM CANADIAN
ROCKIES ACROSS GREAT LAKES TO QUE. RELATED SFC BAROCLINIC ZONE --
NOW DEVELOPING OVER NRN HIGH PLAINS E OF CANADIAN ROCKIES -- WILL
STRENGTHEN AND MOVE SEWD ACROSS NRN/CENTRAL PLAINS BY 23/12Z. ERN
PORTION OF FRONT THEN SHOULD MOVE QUICKLY EWD OVER GREAT LAKES.
TRAILING/WRN PORTION WILL SAG SOMEWHAT MORE SLOWLY SWD OVER LOWER MS
VALLEY AND SRN PLAINS...REACHING NRN AL...CENTRAL MS AND S-CENTRAL
TX BY END OF PERIOD. WEAK SFC LOW -- INITIALLY MORE LEE-SIDE IN
ORIGIN -- SHOULD ATTACH TO FRONT OVER CENTRAL HIGH PLAINS DAY-1.
THIS LOW SHOULD EVOLVE/PROPAGATE SSEWD TO CENTRAL TX AHEAD OF
SHORTWAVE TROUGH AS FRONTAL-WAVE FEATURE.
...ARKLATEX...LOWER MS VALLEY REGIONS...
BROAD LOW LEVEL WAA REGIME IS FCST THROUGHOUT PERIOD ACROSS THIS
REGION...IN ADVANCE OF SFC COLD FRONT AND MID-UPPER SHORTWAVE
TROUGH. ALTHOUGH AIR MASS MODIFICATION IN UPSTREAM/GULF
TRAJECTORIES WILL BE RATHER IMMATURE...SUFFICIENT MOISTENING IS
EXPECTED BY SECOND HALF OF PERIOD TO SUPPORT CONVECTIVE DEVELOPMENT
INVOF FRONTAL ZONE. THIS ACTIVITY MAY DEEPEN GRADUALLY AND
EXPAND/SHIFT EWD -- AS CONTINUED ISENTROPIC LIFT OF PROGRESSIVELY
MORE MOIST PARCELS TO LFC OCCURS OVER BROADER AREA...AND
PRECONVECTIVE BUOYANCY ROOTED IN ELEVATED INFLOW LAYER SLOWLY
INCREASES. ELEVATED MUCAPE 200-600 J/KG IS POSSIBLE DURING
24/03Z-24/12Z TIME FRAME. RELATIVELY WEAK EFFECTIVE SHEAR AND LACK
OF MORE ROBUST INSTABILITY EACH SUGGEST CONVECTION WILL REMAIN TOO
DISORGANIZED FOR SVR PROBABILITIES TO BE INTRODUCED ATTM.
LAPSE RATES SHOULD BE STEEPER ALOFT WITH SWWD EXTENT ACROSS CENTRAL
TX -- IN CLOSER PROXIMITY TO CORE REGION OF ELEVATED MIXED-LAYER AIR
MASS. HOWEVER...CAPPING NEAR BASE OF THAT PLUME AND LACK OF GREATER
MOISTURE WILL COMBINE TO LIMIT POTENTIAL FOR DEVELOPMENT.
...ERN CA/WRN NV...
SUFFICIENT COOLING ALOFT...LOW LEVEL WAA AND RELATED STEEPENING OF
LAPSE RATES MAY OCCUR INVOF SIERRA NV RANGE TO SUPPORT MIDLEVEL
CONVECTION. FCST SOUNDINGS INDICATE WEAK CAPE -- GENERALLY AOB 150
J/KG -- MAY EXTEND INTO FAVORABLE ICING LAYERS...AND THAT VERY
BRIEF/ISOLATED LIGHTNING IS POSSIBLE. ATTM...PROBABLE
COVERAGE/DURATION APPEAR TOO MRGL TO WARRANT GEN THUNDER OUTLOOK.
..EDWARDS.. 01/22/2009
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