SWODY2
SPC AC 240526
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 AM CDT FRI OCT 24 2008
VALID 251200Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE MIDDLE
ATLANTIC STATES...
...SYNOPSIS...
LARGE-SCALE PATTERN WILL REMAIN QUITE DYNAMIC THROUGH THE DAY TWO
PERIOD AS POWERFUL UPPER JET DIGS SEWD FROM WRN CANADA INTO THE
GREAT LAKES REGION. IN RESPONSE...CLOSED MID AND UPPER LEVEL LOW
INITIALLY OVER THE MIDWEST WILL EVOLVE INTO AN OPEN WAVE...LIFTING
NEWD IN NEGATIVE-TILT FASHION THROUGH THE LOWER GREAT LAKES AND NEW
ENGLAND. THIS EVOLUTION WILL RESULT IN A CORRIDOR OF SIGNIFICANT
HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT DEVELOPING NEWD THROUGH THE
NERN CONUS.
AT THE SURFACE...COLD FRONT ATTENDANT TO THE EJECTING MIDLEVEL
TROUGH WILL RAPIDLY SHIFT EWD THROUGH THE LOWER GREAT LAKES...NEW
ENGLAND AND MIDDLE ATLANTIC STATES SATURDAY INTO SATURDAY NIGHT. A
WARM FRONT WILL RAPIDLY LIFT NWD THROUGH THE MIDDLE/LOWER HUDSON
VALLEY AND CNTRL/SRN NEW ENGLAND IN ADVANCE OF COLD FRONT.
...SRN NEW ENGLAND SWD THROUGH THE MIDDLE ATLANTIC STATES...
50-60+ KT SSELY LLJ WILL ENHANCE THE NWD TRANSPORT OF AN
INCREASINGLY MOIST BOUNDARY LAYER OFF THE WRN ATLANTIC WITH
DEWPOINTS INCREASING THROUGH THE 60S ACROSS SYSTEM WARM SECTOR.
HOWEVER...CONSIDERABLE CLOUDS AND ANTECEDENT PRECIPITATION WILL
IMPEDE DIABATIC HEATING AND AIR MASS DESTABILIZATION WITH MLCAPE
LIKELY REMAINING BELOW 500 J/KG. THE SRN FRINGE OF STRONGEST HEIGHT
FALLS /DELINEATED BY 80-90+ KT MIDLEVEL JET STREAK ROTATING THROUGH
THE TROUGH BASE/ WILL LIFT NEWD FROM THE ALLEGHENY RANGE INTO THE
HUDSON VALLEY AND NEW ENGLAND...ALONG THE NRN EXTENSION OF EXPANDING
WARM SECTOR. THIS FORCING IS EXPECTED TO CONTRIBUTE TO AN INCREASE
IN STORM COVERAGE AND INTENSITY BY EARLY AFTERNOON ALONG AND AHEAD
OF COLD FRONT FROM ERN NC NWD THROUGH THE DELMARVA AND EVENTUALLY
INTO THE LOWER HUDSON VALLEY.
GIVEN THE VERY STRONG AMBIENT SHEAR /BOTH IN THE LOW LEVELS AND
THROUGH A DEEP LAYER/...NAMELY FROM THE TIDEWATER NWD...THE HIGHER
SEVERE PROBABILITIES AND CATEGORICAL SLIGHT RISK ARE CONDITIONAL ON
SUFFICIENT INSTABILITY TO SUSTAIN TSTM UPDRAFTS. ANY LONGER-LIVED
STORMS THAT CAN DEVELOP AND PERSIST WILL BE CAPABLE OF EVOLVING INTO
SUPERCELLS OR BOWING/LEWP STRUCTURES EMBEDDED IN THE LARGER-SCALE
PRECIPITATION SHIELD. DAMAGING WIND GUSTS AND PERHAPS A TORNADO OR
TWO WOULD BE THE PRIMARY HAZARDS WITH THESE STORMS.
STRONGLY-FORCED CONVECTION WILL MOVE/DEVELOP EWD/NEWD THROUGH PARTS
OF THE HUDSON VALLEY AND NEW ENGLAND LATER SATURDAY AFTERNOON AND
SATURDAY NIGHT IN ADVANCE OF MIDLEVEL TROUGH AND SURFACE COLD FRONT.
VERTICAL SHEAR WILL REMAIN VERY STRONG...BUT INSTABILITY IS FORECAST
TO BE QUITE MARGINAL AND PERHAPS SUPPORTIVE OF STORMS SLIGHTLY
ELEVATED ABOVE A NEAR SURFACE STABLE LAYER. THEREFORE...ONLY LOW
SEVERE WEATHER PROBABILITIES WILL BE INCLUDED ATTM.
..MEAD.. 10/24/2008
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