MESO: Mesoscale Discussion 2215

ACUS11 KWNS 291523
SWOMCD
SPC MCD 291522
RIZ000-MAZ000-CTZ000-NYZ000-NHZ000-VTZ000-NJZ000-PAZ000-291645-

MESOSCALE DISCUSSION 2215
NWS STORM PREDICTION CENTER NORMAN OK
1022 AM CDT THU SEP 29 2011

AREAS AFFECTED...ERN PA/SERN NY/NRN NJ/SRN VT/SWRN NH/WRN MA/CT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 291522Z - 291645Z

STORMS WILL CONTINUE INCREASING ACROSS ERN PA/SRN NY/NRN NJ OVER THE
NEXT HOUR...AND SPREAD NNEWD INTO SRN NEW ENGLAND. CORRESPONDING
RAMP-UP IN SEVERE POTENTIAL MAY REQUIRE WW ISSUANCE BY EARLY
AFTERNOON.

LATEST VISIBLE SATELLITE IMAGERY SHOWS FAIRLY EXPANSIVE -- BUT
LOCALLY BROKEN -- CLOUD COVER ACROSS ERN PA AND INTO SERN NY...AHEAD
OF AN ADVANCING COLD FRONT. HEATING THROUGH THE BROKEN CLOUDS
COMBINED WITH DEWPOINTS IN THE 60S TO NEAR 70 IS RESULTING IN MODEST
DESTABILIZATION -- WHICH SHOULD CONTINUE INTO THE EARLY AFTERNOON.

WV IMAGERY CONFIRMS THE RAPID APPROACH OF A LOBE OF VORTICITY
ROTATING AROUND THE MAIN LOW -- WITH THE VORT CENTER EVIDENT ACROSS
WRN PA AND MOVING QUICKLY NEWD WITH TIME. AS THIS VORT LOBE SHIFTS
ACROSS THE APPALACHIANS TOWARD THE MID-ATLANTIC REGION AND NEW
ENGLAND...CONVECTION -- FUELED BY THE DESTABILIZING AIRMASS --
SHOULD EXPAND BOTH ALONG AND AHEAD OF THE SURFACE COLD FRONT.

MODELS FORECAST A COMPACT 50-PLUS KT H5 JET ON THE ERN SIDE OF THE
AFOREMENTIONED VORT LOBE -- CONFIRMED BY KCCX /STATE COLLEGE PA/ VWP
-- TO SPREAD ACROSS THE WARM SECTOR OVER THE NEXT FEW
HOURS...PROVIDING SHEAR SUFFICIENT TO SUPPORT UPDRAFT
ORGANIZATION/ROTATION WITHIN DEVELOPING STORMS. WHILE LAPSE RATES
REMAIN MODEST PER MORNING RAOBS WHICH WILL LIMIT BUOYANCY...THREAT
FOR DAMAGING WINDS IS APPARENT -- PARTICULARLY IF STORMS CAN GROW
UPSCALE INTO LINE SEGMENTS ALONG/AHEAD OF THE FRONT. THIS THREAT --
COMBINED WITH POTENTIAL FOR ISOLATED HAIL AND POSSIBLY EVEN AN
ISOLATED TORNADO -- SUGGESTS THAT WW WILL BE REQUIRED...PERHAPS AS
EARLY AS THE LUNCHTIME HOUR.

..GOSS.. 09/29/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...GYX...BOX...BTV...OKX...ALY...PHI...BGM...CTP...

LAT...LON 40327479 40737582 42127500 43087405 43377323 43147225
42347183 40947180 40277390 40327479

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