[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 100613
SWODY2
SPC AC 100613

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0113 AM CDT TUE OCT 10 2006

VALID 111200Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS CENTRAL GULF COAST REGION TO
OH/WRN PA...

...SYNOPSIS...
SIGNIFICANT PATTERN SHIFT UNDERWAY...AS UPPER LOW NOW INTENSIFYING
OVER NRN NV RETROGRADES OFFSHORE CA.  ANOTHER UPPER LOW -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY OVER FAR NRN MB -- WILL DIG
SWD...PHASE WITH OTHER SHORTWAVE PERTURBATIONS -- AND
ENLARGE/INTENSIFY MARKEDLY.  BY END OF DAY-2 PERIOD...THIS PROCESS
WILL RESULT IN LARGE...DEEP...COLD CYCLONIC VORTEX COVERING MOST OF
CENTRAL/ERN CONUS AND CENTERED OVER UPPER GREAT LAKES. SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER WRN NM -- IS
FCST TO EJECT EWD AND DEAMPLIFY DAY-1...AMIDST STRENGTHENING LARGE
SCALE HEIGHT GRADIENTS ASSOCIATED WITH DIGGING POLAR VORTEX.

AT SFC...FRONTAL ZONE NOW ANALYZED FROM NY...SWWD OVER OH AND OZARKS
TO SW TX -- WILL BE OVERCOME BY INTENSE/SECONDARY COLD FRONTAL SURGE
DURING THIS PERIOD.  ASSOCIATED SFC CYCLOGENESIS SHOULD OCCUR OVER
UPPER MS VALLEY REGION BY 11/12Z...WITH RESULTANT CYCLONE LIFTING
NEWD ACROSS LS/UPPER MI REGION INTO ONT...BECOMING VERTICALLY
STACKED WITH MIDLEVEL VORTEX...AND OCCLUDING.  BY END OF
PERIOD...SFC COLD FRONT SHOULD EXTEND FROM SWRN QUE OR SERN
ONT...SWD ACROSS CAROLINAS...THEN SWWD ACROSS DEEP S TX.  SREF DATA
UNAVAILABLE...AND SPECTRAL MODEL STILL APPEARS TO BE TOO SLOW WITH
COLD FRONT OVER TX.  HOWEVER...PREVIOUSLY TOO-AGGRESSIVE OPERATIONAL
WRF HAS SLOWED CONSIDERABLY IN 24 HOURS AND IS CLOSER TO ECMWF/UKMET
CONSENSUS...WHICH REMAINS FAVORED FRONTAL SCENARIO.

...OH VALLEY TO CENTRAL GULF COAST...
SCATTERED TSTMS IN BANDS AND CLUSTERS SHOULD FORM WITHIN OUTLOOK
AREA DURING DAYLIGHT HOURS...MAIN SVR RISK BEING DAMAGING GUSTS. 
SVR POTENTIAL SHOULD DIMINISH CONSIDERABLY AFTER DARK...PARTICULARLY
FROM TN NWD...AS ALREADY MRGL INSTABILITY WEAKENS.  SFC-BASED CAPE
WILL BE LIMITED ACROSS MUCH OF THIS AREA BY COMBINATION OF WEAK
MIDLEVEL LAPSE RATES -- JUST ABOVE MOIST-ADIABATIC -- AND PRESENCE
OF CLOUD COVER TO LIMIT SFC SOLAR HEATING.  HOWEVER...EXPECT CINH TO
BE WEAK AS WELL...PERMITTING CONVECTION TO DEVELOP IN ONE OR MORE
LINEAR ZONES OF FAVORABLE CONVERGENCE ALONG/AHEAD OF SFC COLD FRONT.

IN OH VALLEY/LE REGION...WEAK MIDLEVEL ASCENT -- ASSOCIATED WITH
EJECTING REMAINS OF CURRENT SWRN TROUGH -- MAY PROVIDE SOME COOLING
ALOFT IN SUPPORT OF CONVECTION.  FCST SOUNDINGS SUGGEST ABOUT 30 DEG
MEAN WIND COMPONENT ACROSS FRONTAL ZONE IS POSSIBLE...SUPPORTING
NARROW BAND OF CONVECTION MOVING NEWD INTO ENVIRONMENT OF SFC DEW
POINTS MID-UPPER 50S...AND AROUND 500 J/KG MLCAPES.

PREFRONTAL LOW LEVEL FLOW GENERALLY SHOULD VEER WITH SWD
EXTENT...RELATED TO INCREASING DISTANCE FROM LARGEST PRESSURE FALLS
THAT ARE FCST TO OCCUR AHEAD OF EJECTING SFC CYCLONE. 
HOWEVER...GIVEN STRENGTH OF GRADIENT FLOW ALOFT...DEEP-LAYER SHEAR
STILL WILL BE FAVORABLE FOR SVR.  PRIND SFC MOISTURE AND POTENTIAL
FOR AREAS OF DIABATIC HEATING WILL INCREASE SWD.  NEARLY
UNIDIRECTIONAL DEEP-LAYER WIND PROFILES ARE FCST...SUPPORTING MORE
MULTICELLULAR/LINEAR MODES...ALTHOUGH ANY DISCRETE DEVELOPMENT WILL
HAVE SUPERCELL POTENTIAL.  RELATIVE MIN IN SVR POTENTIAL MAY EXIST
BETWEEN OH VALLEY AND GULF STATES REGIMES...WHERE CONVERGENCE AND
HEATING EACH REMAIN RELATIVELY WEAK...HOWEVER THIS IS TOO UNCERTAIN
AND MESOSCALE DEPENDENT TO WARRANT BREAKING OUTLOOK INTO TWO
DISTINCT CATEGORICAL AREAS ATTM.

...COASTAL/TIDEWATER VA/NC...
WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP OVER PORTIONS OF
THIS REGION -- SFC-BASED DURING DAYLIGHT HOURS ALONG/S OF FRONT.
MID-UPPER LEVEL GRADIENT FLOW IS FCST TO STRENGTHEN WITH TIME IN
TANDEM WITH SFC HEATING...WHILE LOW LEVEL MOIST ADVECTION FROM
ATLANTIC MAINTAINS/INCREASES BOUNDARY LAYER MOISTURE. 
MEANWHILE...ALTHOUGH LOW LEVEL WINDS ARE FCST TO REMAIN RATHER WEAK
IN WARM SECTOR -- GENERALLY 10 KT OR LESS -- FLOW SHOULD BE SLIGHTLY
STRONGER AND SOMEWHAT BACKED IN SFC FRONTAL ZONE.  THIS COMBINATION
OF FACTORS SUGGESTS AT LEAST MRGL SVR POTENTIAL WITH A FEW TSTMS.

..EDWARDS.. 10/10/2006