[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 121738
SWODY2
SPC AC 121737

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1237 PM CDT TUE SEP 12 2006

VALID 131200Z - 141200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
PROGRESSIVE SYNOPTIC PATTERN WILL FEATURE HEIGHT FALLS LATE DAY-2
ACROSS PACIFIC NW AND NRN ROCKIES...ACCOMPANIED BY SEWD SHIFT OF
UPPER RIDGING FROM NRN ROCKIES TO SRN/CENTRAL PLAINS.  AS THIS
OCCURS...DOWNSTREAM UPPER LOW -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY OVER MN/IA BORDER -- IS EXPECTED TO TURN SEWD THEN EWD
BETWEEN OH VALLEY AND GREAT LAKES.  THIS FEATURE SHOULD EVOLVE TO
OPEN-WAVE TROUGH IN PHASE WITH PREVIOUSLY DETACHED SHORTWAVE NOW
DIGGING SEWD ACROSS NERN NM AND TX PANHANDLE.  BY END OF
PERIOD...COMBINED TROUGH SHOULD EXTEND FROM ERN GREAT LAKES SWWD TO
CENTRAL GULF COAST.

ASSOCIATED SFC LOW -- NOW ANALYZED INVOF IL/WI BORDER -- IS FCST TO
MOVE NEWD ACROSS SRN PORTIONS ONT/QUE DAY-2...AS TRAILING COLD FRONT
MOVES SEWD OVER TN VALLEY...SRN APPALACHIANS...AND PORTIONS FL
PANHANDLE.  OPERATIONAL/DETERMINISTIC MODELS AND MANY SREFX MEMBERS
NOW INDICATE DEVELOPMENT OF WEAK FRONTAL-WAVE LOW BY EARLY IN PERIOD
ACROSS AL...SUBSEQUENTLY MOVING EWD OR NEWD ACROSS GA...POTENTIALLY
LINKING WITH DAMMING/PIEDMONT FRONT.  PROGS ARE QUITE INCONSISTENT
WITH STRENGTH OF THIS FEATURE THROUGHOUT PERIOD...AND WITH TRACK
AFTER ABOUT 14/00Z.

...OH VALLEY...LOWER GREAT LAKES REGION...
BAND OF TSTMS MAY DEVELOP LATE MORNING INTO AFTERNOON AND MOVE ENEWD
ACROSS THIS AREA.  MAIN CONCERN ATTM IS AMOUNT/EXTENT OF FAVORABLE
INSTABILITY...GIVEN LIKELIHOOD OF AMBIENT CLOUD COVER LIMITING SFC
DIABATIC HEATING...AND MIDLEVEL LAPSE RATES JUST SLGTLY GREATER THAN
MOIST ADIABATIC.  NNE-SSW ORIENTED CORRIDOR OF LARGE SCALE ASCENT --
NEARLY PARALLEL TO FRONT AND JUST AHEAD OF MID-UPPER TROUGH --
SHOULD ENHANCE LAPSE RATES JUST ENOUGH TO SUPPORT SOME SFC-BASED
BUOYANCY...PROBABLY AOB 500 J/KG MOST AREAS.  DEEP-LAYER WIND
PROFILES WILL BE LARGELY UNIDIRECTIONAL WITH WEAK COMPONENT OF MEAN
FLOW ACROSS POTENTIAL FORCING BOUNDARY.  THEREFORE SVR POTENTIAL
APPEARS TOO CONDITIONAL/MRGL FOR CATEGORICAL OUTLOOK ATTM.

...SERN CONUS...
SCATTERED TSTMS ARE LIKELY THROUGH MUCH OF PERIOD ACROSS THIS
REGION...AMIDST REGIME OF LOW LEVEL WAA AND INCREASINGLY RICH
MOISTURE.  SOME OF THESE MAY BECOME SUPERCELLS WITH POTENTIAL FOR
MRGL HAIL...DAMAGING GUST OR BRIEF TORNADO.  WITH CINH EXPECTED TO
BE WEAK...AFTERNOON/EARLY EVENING CONVECTION MAY BECOME SFC
BASED...WITH STRONG INSOLATION IN ANY RELATIVELY CLOUD-FREE AREAS
HELPING TO OFFSET WEAK MIDLEVEL LAPSE RATES FOR MLCAPE POTENTIALLY
NEAR 1000 J/KG.  MEANWHILE...INCREASING MIDLEVEL GRADIENT WINDS
AHEAD OF MID-UPPER TROUGH WILL ENHANCE 0-6 KM SHEAR...PARTICULARLY
OVER INLAND AREAS AL/GA/SC.  MEANWHILE POTENTIAL EXISTS FOR BACKED
SFC FLOW INVOF SFC LOW...CONTRIBUTING TO MESOSCALE AREA OF ENLARGED
0-3 KM AGL HODOGRAPHS. CONSIDERABLE UNCERTAINTY EXISTS ABOUT
STRENGTH OF HEATING/DESTABILIZATION...AND AS MENTIONED
ABOVE...REGARDING TRACK/STRENGTH OF WAVE LOW.  THEREFORE WILL KEEP
TOTAL SVR PROBABILITIES MRGL ATTM UNTIL MESOSCALE FOCI BECOME BETTER
DEFINED.

...SWRN CONUS...
MID-UPPER LEVEL LOW NOW EVIDENT OVER SWRN AZ IS FCST TO MEANDER
ERRATICALLY ACROSS SRN AZ/NWRN SONORA REGION THROUGH PERIOD. 
ASSOCIATED NW-SE ORIENTED SFC TROUGH -- CONTAINING ONE OR MORE WEAK
LOWS -- SHOULD HELP TO MAINTAIN FETCH OF MOISTENING FLOW FROM
SE...IN LOW-MIDDLE LEVELS.  STEEP DEEP-LAYER LAPSE RATES ARE
POSSIBLE WHEN DIURNAL HEATING IS COMBINED WITH MIDLEVEL COOLING
ASSOCIATED WITH CYCLONE ALOFT. CLOUDS/PRECIP AND CONVECTIVE
STABILIZATION -- RESULTING FROM DAY-1 ACTIVITY -- MAY LIMIT OR FOCUS
POTENTIAL ON MESOSCALE.  STRONGEST STORMS MAY PRODUCE HAIL/GUSTS
NEAR SVR LEVELS.

..EDWARDS.. 09/12/2006