SWODY1
SPC AC 270559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT MON SEP 27 2010
VALID 271200Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN FL PANHANDLE THROUGH
SRN/ERN GA...MUCH OF THE CAROLINAS...CENTRAL/ERN VA TO FAR SERN PA
AND SRN NJ...
...SYNOPSIS...
DEEP CLOSED MID-UPPER LEVEL LOW...CURRENTLY SHIFTING SWD INTO THE
MID SOUTH PER WATER VAPOR IMAGERY...WILL MOVE EWD FROM MS/AL TODAY
REACHING THE SRN APPALACHIANS BY 28/00Z. THIS LOW AND ATTENDANT
TROUGH IS EXPECTED TO BECOME NEGATIVELY-TILTED AS IT LIFTS NNEWD
TOWARD THE UPPER OH VALLEY. GIVEN A STRONG RIDGE OVER THE WRN
ATLANTIC...THE EVOLUTION OF THE ERN U.S. SYSTEM WILL RESULT IN
STRENGTHENING DEEP SSWLY WIND FIELDS THROUGHOUT THE FORECAST PERIOD.
IN THE LOW LEVELS...PRIMARY SYNOPTIC LOW IS FORECAST TO TRACK FROM
CENTRAL/NRN GA EARLY IN THE PERIOD NWD TO ERN OH/WRN PA BY 12Z
TUESDAY...WITH STRONGEST DEEPENING OF THIS FEATURE BETWEEN 28/00-12Z
AS THE UPPER LOW/TROUGH BECOMES NEGATIVELY-TILTED. MEANWHILE...A
SUB-SYNOPTIC SURFACE LOW SHOULD TRACK FROM THE FL PANHANDLE NEWD
ALONG A SURFACE BOUNDARY REACHING THE WRN CAROLINAS THIS
AFTERNOON...AND THEN REACH NRN VA BY THE END OF THE FORECAST PERIOD.
THE NE-SW ORIENTED SURFACE BOUNDARY...INITIALLY STATIONARY FROM THE
CAROLINAS SSWWD TO THE FL PANHANDLE...WILL BEGIN TO MOVE EWD AS A
COLD FRONT ACROSS GA THIS AFTERNOON...AND THEN SPREAD QUICKLY ENEWD
AFTER 28/00Z. THIS FRONT SHOULD EXTEND FROM DELMARVA SWD TO OFF THE
SC/GA COAST TO NRN FL BY 12Z TUESDAY.
...ERN FL PANHANDLE/SRN-ERN GA NEWD TO FAR SERN PA/SRN NJ...
THE TRACK/GEOMETRY OF THE MID-UPPER LEVEL LOW/TROUGH AND ATTENDANT
SYNOPTIC LOW SHOULD ALLOW THE WARM SECTOR OVER VA TO SPREAD WWD TO
IN LEE OF THE HIGHER TERRAIN...WHILE STRENGTHENING SLY LOW LEVEL
WINDS SUPPORT THE WARM SECTOR ALSO MOVING NWD INTO THE MID ATLANTIC
STATES. A MOIST AIR MASS CURRENTLY RESIDING ACROSS THE SERN STATES
TO CAROLINAS WILL SPREAD NWD...WITH PRECIPITABLE WATER VALUES 2+
INCHES REACHING DELMARVA TO SRN NEW ENGLAND BY THIS AFTERNOON...AS
THE WARM FRONT ADVANCES NWD. DESPITE WEAK LAPSE RATES ACROSS THE
WARM SECTOR...RICH MOISTURE WILL SUPPORT MUCAPE VALUES MAINLY
RANGING 500-1000 J/KG. MUCAPE AROUND 1000 J/KG IS POSSIBLE FROM ERN
FL PANHANDLE TO SRN SC AND ACROSS FAR ERN NC WHERE SURFACE DEWPOINTS
WILL BE INTO THE LOWER 70S. ANY SURFACE HEATING WILL SUPPORT A
BOOST IN INSTABILITY AND OVERALL SEVERE WEATHER THREAT.
MODELS SUGGEST TSTMS...SOME POSSIBLY SEVERE...MAY BE ONGOING AT 12Z
TODAY FROM THE ERN FL PANHANDLE INTO SWRN GA...WITH ADDITIONAL
SHOWERS/TSTMS EXTENDING NEWD THROUGH THE ERN CAROLINAS. THIS
ACTIVITY WILL SPREAD ENEWD...WITH ADDITIONAL STORMS EXPECTED TO
DEVELOP ALONG THE SURFACE FRONT IN THE WAKE OF THE INITIAL TSTMS.
AS STRONG FORCING FOR ASCENT SPREADS ACROSS THE SLIGHT RISK AREA
BETWEEN 27/18-28/06Z AND WIND FIELDS/DEEP LAYER SHEAR
STRENGTHEN...TSTMS SHOULD BE FORM INTO LINES AND QLCS WITH AN
ATTENDANT THREAT FOR DAMAGING WINDS AND A FEW TORNADOES. THE LATTER
WILL BE POSSIBLE GIVEN INCREASING LOW LEVEL HODOGRAPH CURVATURE AS
THE LLJ INCREASES THROUGH THE PERIOD. THE GREATEST THREAT FOR
DAMAGING WINDS SHOULD EXTEND FROM SOUTH CENTRAL-ERN GA THROUGH THE
CENTRAL CAROLINAS TO SRN VA AS THIS REGION WILL RESIDE BENEATH
STRONG SSWLY H85-H70 FLOW /40-50 KT/.
DESPITE MARGINAL INSTABILITY EXPECTED OVERNIGHT AHEAD OF THE COLD
FRONT...THE RICH MOISTURE AND STRONG WIND FIELDS WITH FAVORABLE LOW
LEVEL SHEAR SUGGESTS A THREAT FOR STRONG WINDS AND AN ISOLATED
TORNADO CANNOT BE RULED OUT THROUGH 12Z TUESDAY. THESE OVERNIGHT
THREATS SHOULD BE CONFINED FROM ERN NC/VA TO SERN PA/SRN NJ.
..PETERS/HURLBUT.. 09/27/2010
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