SWODY1
SPC AC 231234
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0734 AM CDT FRI SEP 23 2011
VALID 231300Z - 241200Z
...NO SVR TSTM AREAS FORECAST...
...LOWER GREAT LAKES/UPPER OH VALLEY...
STRONG VORTICITY MAXIMUM OVER THE LOWER OH VALLEY WILL ROTATE NNEWD
THROUGH ERN PERIPHERY OF UPPER LOW...SUPPORTING AN INCREASE IN
FORCING FOR ASCENT AND MIDLEVEL FLOW ACROSS THE REGION TODAY. IN
THE LOW LEVELS...WEAK FRONTAL WAVE WILL DEVELOP NWD THROUGH THE
UPPER OH VALLEY INTO SWRN ONTARIO WHILE TRAILING COLD FRONT ADVANCES
EWD THROUGH THE LOWER GREAT LAKES AND CNTRL APPALACHIANS.
WHILE WIDESPREAD CLOUDS AND MARGINAL BOUNDARY LAYER MOISTURE CONTENT
WILL LIMIT AIR MASS DESTABILIZATION TODAY...THE NEWD PROGRESSION OF
MIDLEVEL DRY SLOT MAY YIELD SOME CLOUD BREAKS AND POCKETS OF WEAK
INSTABILITY. FRONTAL ASCENT COUPLED WITH INCREASED LARGE-SCALE
FORCING ATTENDANT TO ABOVE-MENTIONED VORTICITY MAXIMUM MAY FOSTER AN
INCREASE IN TSTM COVERAGE BY AFTERNOON FROM WRN PARTS OF NY/PA INTO
THE CNTRL APPALACHIANS. DESPITE STRENGTHENING MID- AND HIGH-FLOW
FLOW AND RESULTANT LENGTHENING HODOGRAPHS...FORECAST SOUNDINGS
SUGGEST THAT BULK OF POTENTIAL BUOYANCY WILL RESIDE GENERALLY BELOW
500 MB WHERE WIND FIELD WILL BE WEAKER. THIS COMBINED WITH THE WEAK
INSTABILITY WILL LIKELY LIMIT ORGANIZED SEVERE WEATHER POTENTIAL
LATER TODAY.
...CAROLINAS TO MID-ATLANTIC COAST...
MORNING WATER VAPOR IMAGERY SHOWS A WEAK VORTICITY MAXIMUM OVER THE
SRN APPALACHIANS WHICH WILL CONTINUE NNEWD TODAY WITHIN
DEEP-MERIDIONAL FLOW REGIME PRESENT DOWNSTREAM FROM GREAT LAKES
UPPER LOW. FORCING FOR ASCENT ASSOCIATED WITH THIS IMPULSE IS
EXPECTED TO SUPPORT AN INCREASE IN TSTM ACTIVITY THROUGH THE DIURNAL
HEATING CYCLE WITHIN A MOIST AIR MASS CHARACTERIZED BY DEW POINTS IN
THE UPPER 60S TO LOWER 70S AND PW VALUES OF 1.5-2.0+ INCHES. HERE
TOO...WIDESPREAD CLOUDS AND WEAK LAPSE RATES WILL LIMIT AIR MASS
DESTABILIZATION...WITH MLCAPE VALUES REMAINING GENERALLY BELOW 1000
J/KG ACROSS THE WARM SECTOR.
LATEST MODEL GUIDANCE INDICATES AN INCREASE IN LOW-LEVEL WINDS BY
AFTERNOON ALONG THE MID-ATLANTIC COAST...RESULTING IN VERTICALLY
VEERING WIND PROFILES AND SUFFICIENT SHEAR FOR ROTATING STORMS.
WHILE LOCALLY DAMAGING WET MICROBURSTS AND/OR A BRIEF TORNADO ARE
POSSIBLE...THE MARGINAL INSTABILITY IS EXPECTED TO PRECLUDE A MORE
SUBSTANTIAL SEVERE WEATHER THREAT.
..MEAD/ROGERS.. 09/23/2011
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