MESO: Mesoscale Discussion 0802

ACUS11 KWNS 181834
SWOMCD
SPC MCD 181834
NJZ000-NYZ000-PAZ000-181930-

MESOSCALE DISCUSSION 0802
NWS STORM PREDICTION CENTER NORMAN OK
0134 PM CDT WED MAY 18 2011

AREAS AFFECTED...PARTS OF ERN PA AND CENTRAL/NRN NJ

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 181834Z - 181930Z

WW IS POSSIBLE THIS AFTERNOON ACROSS PARTS OF ERN PA AND CENTRAL/NRN
NJ. THIS POTENTIAL WILL BE GREATER IF INSTABILITY INCREASES BEYOND
THE CURRENT MARGINAL VALUES AND RADAR TRENDS SUGGEST MORE PERSISTENT
UPDRAFTS.

SURFACE ANALYSES INDICATED A CORRIDOR OF GREATER MOISTURE EXTENDING
INLAND FROM THE NJ COAST INTO ERN PA...WITH VALUES IN THE LOWER 60S
ACROSS MUCH OF NJ INTO EAST CENTRAL/SERN PA AND NEAR 60 IN NERN PA.
ALTHOUGH CLOUDINESS HAS LIMITED SURFACE HEATING/ DESTABILIZATION AND
WEAKER MIDLEVEL LAPSE RATES EXIST ACROSS THIS AREA...MUCAPE IS
RANGING FROM 500-1000 J/KG. THE MARGINAL INSTABILITY AND LAPSE
RATES SUGGEST INDIVIDUAL STORMS MAY STRUGGLE TO ATTAIN PERSISTENT
UPDRAFTS...AND THUS POSE A SUFFICIENT THREAT FOR STRONG TO SEVERE
TSTM COVERAGE THAT WOULD WARRANT A SEVERE WEATHER WATCH.

DESPITE THE MARGINAL INSTABILITY...KINEMATICS ARE FAVORABLE FOR
STORM ORGANIZATION AND SOME ROTATION. TRENDS IN LOW LEVEL FLOW PER
OBJECTIVE ANALYSES AND AREA WSR-88D VWPS INDICATED AN INCREASE IN
WIND SPEEDS WITH SOME BACKING TO SELY. THIS IS RESULTING IN AN
INCREASE IN LOW LEVEL SHEAR FOR STORM ROTATION. STRONGER ESELY
MIDLEVEL WINDS/DEEP SHEAR WILL CONTINUE TO INCREASE THIS AFTERNOON
AS THE ATTENDANT CLOSED LOW LOCATED OVER THE CENTRAL APPALACHIANS
SHIFTS NWD. REGIONAL RADAR IMAGERY SHOWED AN AREA OF SHOWERS/
EMBEDDED TSTMS EXTENDING FROM SERN PA THROUGH CENTRAL/NRN NJ AND
OFFSHORE...WITH A FEW OF THE STORMS INDICATING PERIODIC LOW LEVEL
ROTATIONAL COUPLETS.

..PETERS.. 05/18/2011

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

ATTN...WFO...OKX...PHI...BGM...CTP...

LAT...LON 39697423 39987539 40347657 40807703 41587662 41697574
41317473 40887420 40457406 39827398 39697423

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