SWODY2
SPC AC 091742
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1242 PM CDT WED MAY 09 2007
VALID 101200Z - 111200Z
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MT/NRN ID...
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS S TX...
..SYNOPSIS...
COMPLEX UPPER AIR PATTERN FCST ACROSS CONUS THROUGH DAY-2. RIDGING
FCST TO INTENSIFY ACROSS 4-CORNERS REGION AS UPPER LOW NOW OVER FAR
W TX IS FCST TO MOVE ESEWD TO UPPER TX COASTAL PLAIN BY END OF
PERIOD. MEANWHILE...NRN STREAM MID-UPPER LEVEL LOW PRESENTLY OVER
UPPER GREAT LAKES IS FCST TO MOVE EWD AND WEAKEN SLIGHTLY INTO
OPEN-WAVE CONFIGURATION...CROSSING ERN GREAT LAKES...NY AND PA
THROUGH PERIOD. ASSOCIATED WEAK SFC FRONTAL ZONE LIKEWISE WILL MOVE
EWD ACROSS NRN APPALACHIANS/ERN GREAT LAKES REGION.
FARTHER SW...VERY COMPLEX/SUBTLE SFC PATTERN EXPECTED TO CONTINUE
THROUGH DAY-2 WITH NUMEROUS CONVECTIVE BOUNDARIES AND WEAK TROUGHS.
PRIMARY/WEAK SFC LOW SHOULD DEVELOP ACROSS CENTRAL/SRN TX IN
CONTINUITY WITH MID/UPPER VORTEX.
..W GULF COAST REGION TO ARKLATEX...
TSTMS MAY BE ONGOING ACROSS CENTRAL/SRN TX EARLY IN PERIOD...WITH
POTENTIAL FOR STG/ISOLATED SVR GUSTS AND HAIL. ANY SUCH ACTIVITY
SHOULD WEAKEN DURING MORNING.
AFTERNOON BOUNDARY LAYER AIR MASS ACROSS THIS REGION SHOULD BE
CHARACTERIZED BY POCKETS OF FAVORABLE SFC THETAE AND SFC-BASED
BUOYANCY. SVR POTENTIAL WILL BE FRAGMENTED IN SPACE AND
TIME...RELATED TO THREE MAIN FACTORS...
1. MESOSCALE BOUNDARIES LEFT BEHIND BY PRIOR CONVECTION...WHICH
SHOULD ACT AS PRIMARY FOCI FOR AFTERNOON/EVENING DEVELOPMENT...
2. REGIONALLY BKN CLOUD/PRECIP COVER WITH MOST FAVORABLE DIABATIC
HEATING IN RELATIVELY CLEAR AREAS...
3. INTERWEAVING OF MOIST W GULF/NE MEX AIR MASS AND RELATIVELY DRY
TRAJECTORIES EMANATING FROM CONTINENTAL RIDGING THAT HAS BEEN
PERSISTENT W-NW OF ANDREA.
KINEMATICALLY...MOST FAVORABLE VERTICAL SHEAR PROFILE ARE PROGGED
AROUND SRN RIM OF MID/UPPER LOW...WHERE 35-45 KT WLY 500 MB FLOW AND
WEAK SFC SELYS WILL CONTRIBUTE TO ENHANCED DEEP-LAYER SHEAR. FOR
THIS REASON...ORGANIZED SVR PROBABILITIES ARE MAXIMIZED ACROSS S
TX...THOUGH ISOLATED/SPORADIC GUSTS OR HAIL NEAR SVR LIMITS WILL BE
POSSIBLE ACROSS BROAD AREA FROM TX COAST THROUGH ARKLATEX AND LOWER
MS VALLEY.
..NRN ROCKIES...
SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OFFSHORE
CA -- IS EXPECTED TO ACCELERATE NEWD AS IT BECOMES BETTER ENTRAINED
IN NRN STREAM FLOW BELT. THIS PERTURBATION IS FCST TO MOVE ACROSS
INTERIOR PACIFIC NW AND NRN ROCKIES DURING DAY...ENHANCING MIDLEVEL
LAPSE RATES THROUGH ASSOCIATED LARGE SCALE ASCENT/COOLING. STRONG
DEEP-LAYER SHEAR PROFILES ARE EXPECTED BENEATH 45-55 KT 500 MB FLOW.
MEANWHILE...DIABATIC SFC HEATING...PARTICULARLY OF HIGHER
TERRAIN....AND AT LEAST MRGL BOUNDARY LAYER MOISTURE WILL CONTRIBUTE
TO TSTM FORMATION. A FEW ORGANIZED CLUSTERS/LINES OF ACTIVITY MAY
MOVE RAPIDLY NEWD TO EWD ACROSS OUTLOOK AREA...DAMAGING GUSTS BEING
MAIN THREAT AND ISOLATED HAIL ALSO POSSIBLE. POTENTIAL SHOULD
DIMINISH CONSIDERABLY AFTER ABOUT 11/6Z.
..NERN CONUS...
ALTHOUGH MID/UPPER SHORTWAVE TROUGH WILL BE WEAKENING
GRADUALLY...SUFFICIENT LARGE SCALE ASCENT SHOULD MOVE ACROSS THIS
REGION TO FAVORABLY STEEPEN LAPSE RATES ALOFT...IN COMBINATION WITH
INSOLATION. MOIST ADVECTION FROM MARINE FLOW STREAM THAT IS
OCCURRING AROUND NRN RIM OF CIRCULATION OF ANDREA...MAY HELP TO
MAINTAIN LOW 60S DEW POINTS NOW OVER PORTIONS PA. WIDELY SCATTERED
TSTMS SHOULD DEVELOP WITH PRIMARY LINEAR CONFIGURATION AND
UNIDIRECTIONAL DEEP-LAYER WINDS...THOUGH SOMEWHAT BACKED SFC FLOW
MAY DEVELOP LOCALLY WITH OROGRAPHIC INFLUENCES. STG-SVR GUSTS AND
ISOLATED HAIL MAY OCCUR. THREAT APPEARS TOO CONDITIONAL ATTM FOR
CATEGORICAL UPGRADE BUT THIS MAY BE REQUIRED IN SUCCEEDING OUTLOOKS.
...SERN CONUS...SUBTROPICAL STORM ANDREA...
HIGHEST SFC THETAE AND STRONGEST LOW LEVEL SHEAR SHOULD REMAIN
OFFSHORE. HOWEVER SMALL PORTION OF FAVORABLY SHEARED/BUOYANT AIR
MASS ALONG NRN RIM OF THIS SYSTEM MAY CONTINUE TO AFFECT COASTAL
AREAS SRN NC...SC AND PERHAPS GA. ATTM...TORNADO RISK APPEARS TO BE
BELOW PROBABILISTIC OR CATEGORICAL THRESHOLDS...BUT SOME
PROBABILITIES MAY NEED TO BE INTRODUCED IN LATER OUTLOOKS IF CHANGES
IN TRACK SHIFT MORE OF FAVORED NE SECTOR INLAND. REF NHC STATEMENTS
UNDER WMO HEADER WTNT21 KNHC FOR LATEST TRACK/INTENSITY GUIDANCE AND
WATCHES/WARNINGS ON THIS SYSTEM.
.EDWARDS.. 05/09/2007
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