SWODY2
SPC AC 131726
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT WED OCT 13 2010
VALID 141200Z - 151200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU AFTN AND EVE ACROSS PARTS
OF THE MID ATLANTIC COAST STATES...
...SYNOPSIS...
AN AMPLIFICATION WITHIN THE MAIN BELT OF WESTERLIES...NOW UNDERWAY
ACROSS THE EASTERN PACIFIC INTO WESTERN NORTH AMERICA...IS EXPECTED
TO TRANSLATE EASTWARD THROUGH THIS FORECAST PERIOD. DOWNSTREAM OF
AN UPPER RIDGE CURRENTLY BUILDING ACROSS THE WESTERN U.S. AND
CANADA...MODELS INDICATE THAT A COUPLE OF DIGGING SHORT WAVE
IMPULSES WILL CONTRIBUTE TO THE EVOLUTION OF DEEPENING LARGE SCALE
TROUGH OVER THE EASTERN U.S. LATE TODAY THROUGH EARLY FRIDAY. THE
CONSOLIDATION OF SEVERAL DISTINCT BRANCHES OF FLOW APPEAR
LIKELY...INCLUDING ONE NOW PRESENT OVER THE EASTERN GULF AND SOUTH
ATLANTIC COAST STATES...ASSOCIATED WITH THE REMNANTS OF A WEAKENING
CLOSED LOW...AND ANOTHER EMERGING FROM THE SUBTROPICAL PACIFIC.
THIS IS PROGGED TO SUPPORT STRONG SURFACE CYCLOGENESIS NEAR THE
MIDDLE ATLANTIC COAST INTO SOUTHERN NEW ENGLAND THURSDAY AND
THURSDAY NIGHT.
LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION WILL LIKELY
CONTRIBUTE TO WIDESPREAD CONVECTIVE DEVELOPMENT AND THUNDERSTORM
ACTIVITY...MOSTLY OFFSHORE. HOWEVER...A WINDOW OF OPPORTUNITY
APPEARS TO EXIST FOR SIGNIFICANT STORM DEVELOPMENT INLAND OF MID
ATLANTIC COASTAL AREAS.
...MID ATLANTIC COAST STATES INTO SOUTHERN NEW ENGLAND...
CONVECTIVE POTENTIAL DURING THIS PERIOD WILL BE LARGELY DEPENDENT ON
THE LOCATION OF THE INITIATION OF STRONGER SURFACE WAVE
DEVELOPMENT...AND THE TRACK OF THE DEEPENING SURFACE CYCLONE.
SPREAD AMONG THE MODELS/MODEL ENSEMBLES HAS BEEN CONSIDERABLE... BUT
THE 13/12Z NAM IS NOW SIMILAR TO THE 13/00Z ECMWF... SUGGESTING
RAPID PRESSURE FALLS MAY COMMENCE ACROSS PARTS OF EASTERN
VIRGINIA...NORTHEASTWARD THROUGH NORTHERN MID ATLANTIC COASTAL AREAS
THURSDAY AFTERNOON AND EVENING. IF THIS OCCURS... POTENTIAL WILL
EXIST FOR NORTHWARD MOISTURE RETURN AND BOUNDARY LAYER
DESTABILIZATION THROUGH THE WARM SECTOR OF THE DEVELOPING SURFACE
LOW...COINCIDENT WITH STRENGTHENING LOW-LEVEL AND DEEP LAYER
VERTICAL SHEAR. INSTABILITY MAY BE WEAK...BUT NAM FORECAST
SOUNDINGS AND HODOGRAPHS ARE SUPPORTIVE OF THE RISK FOR SUPERCELLS
CAPABLE OF PRODUCING TORNADOES...PARTICULARLY ACROSS PARTS OF
SOUTHEASTERN/EASTERN VIRGINIA THROUGH THE DELMARVA PENINSULA
AREA...BEFORE THE LOW MIGRATES OFFSHORE AND BEGINS TO OCCLUDE
THURSDAY NIGHT.
OTHERWISE...DESTABILIZATION AND STRENGTHENING OF DEEP LAYER SHEAR
COULD BECOME SUFFICIENT FOR SEVERE STORMS ALONG AND AHEAD OF THE
TRAILING SURFACE COLD FRONT AS IT ADVANCES ACROSS EASTERN NORTH
CAROLINA.
..KERR.. 10/13/2010
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