MESO: Mesoscale Discussion 1313

ACUS11 KWNS 301833
SWOMCD
SPC MCD 301833
MEZ000-MAZ000-NHZ000-CTZ000-VTZ000-NYZ000-NJZ000-PAZ000-302100-

MESOSCALE DISCUSSION 1313
NWS STORM PREDICTION CENTER NORMAN OK
0133 PM CDT SUN JUN 30 2013

AREAS AFFECTED...PORTIONS PA...SRN NY...NRN NJ...CT...MA..SRN
VT...NH...SWRN MAINE.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 301833Z - 302100Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...LATER-DEVELOPING...NWD EXTENSION OF REGIME DISCUSSED IN
EARLIER SPC MESOSCALE DISCUSSION 1311 WILL RESULT IN FAVORABLE
CONDITIONS FOR ISOLATED SVR EXPANDING NEWD FROM MID-ATLC INTO
PORTIONS SRN/WRN NEW ENGLAND. THIS REGIME MAY BECOME CONTIGUOUS
ACROSS CENTRAL PA WITH INITIALLY SEPARATE AREA OF ISOLATED TO WIDELY
SCATTERED STG-SVR CONVECTION FROM WRN PA TO SRN PORTIONS OF WRN NY.
MAIN CONCERNS ARE WIND GUSTS APCHG SVR LIMITS...CAPABLE OF TREE
DAMAGE AND MINOR DAMAGE TO STRUCTURAL EXTERIORS...AS WELL AS
ISOLATED LARGE HAIL. THREAT APPEARS TOO MRGL/ISOLATED FOR WW.

DISCUSSION...SFC MESOANALYSIS SHOWS ELONGATED AREA OF LOW
PRESSURE...CONTAINING BROAD/QUASISTATIONARY BAROCLINIC ZONE...FROM
NRN NH SWWD ACROSS CENTRAL PA. E OF ASSOCIATED WAVY/ILL-DEFINED
FRONT...AND AWAY FROM PRE-EXISTING OUTFLOWS...SFC INSOLATION AND DEW
POINTS MID-60S TO LOW 70S ARE OFFSETTING WEAK MID-UPPER LEVEL LAPSE
RATES ENOUGH TO YIELD FAVORABLE BUOYANCY. MODIFIED RAOBS AND FCST
SOUNDINGS SUGGEST MLCAPE WILL PEAK BETWEEN 1500-2000 J/KG DURING
NEXT 2-3 HOURS...INVOF THETAE AXIS LOCATED NEAR LNS-POU-CON-LEW
LINE...BEFORE INSTABILITY FIELD BECOMES RATHER FRAGMENTED BY
OUTFLOWS. WRN BRANCH OF THETAE AXIS EXTENDS ACROSS PORTIONS
CENTRAL/WRN PA...IN SUPPORT OF POST-FRONTAL CONVECTION ONGOING IN
THAT AREA...ALSO CAPABLE OF SPORADIC HAIL AND MINOR WIND DAMAGE.
OVER ENTIRE CORRIDOR...LOW-LEVEL FLOW IS WEAK...SUBSTANTIALLY
LIMITING HODOGRAPH SIZE. HOWEVER...35-45 KT EFFECTIVE SHEAR
MAGNITUDES ARE PRESENT AND SHOULD CONTINUE THROUGH AFTN...AIDING AT
LEAST TRANSIENTLY IN TSTM ORGANIZATION.

..EDWARDS/MEAD.. 06/30/2013

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

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

LAT...LON 40618027 41397909 41907782 42187685 42077536 42197427
43207265 44567046 44116977 43137070 42237147 41077359
40457541 39827992 40618027

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