ZCZC SPCSWOMCD ALL
ACUS11 KWNS 211653 
SPC MCD 211653 
VTZ000-NYZ000-PAZ000-211800-

MESOSCALE DISCUSSION 1500
NWS STORM PREDICTION CENTER NORMAN OK
1153 AM CDT TUE JUL 21 2015

AREAS AFFECTED...PENNSYLVANIA...NEW YORK...VERMONT

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 211653Z - 211800Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...FURTHER INTENSIFICATION OF FRONTAL/PRE-FRONTAL
THUNDERSTORM ACTIVITY IS POSSIBLE AS IT ADVANCES SOUTHEASTWARD THIS
AFTERNOON.  SOME OF THIS MAY BE ACCOMPANIED BY LOCALIZED WIND GUSTS
THAT MAY REMAIN MOSTLY BELOW SEVERE CRITERIA...BUT COULD
NEVERTHELESS RESULT IN SPORADIC DAMAGE OF AND RELATING TO
TREES/NEARBY POWER LINES.  A WATCH IS NOT CURRENTLY
ANTICIPATED...BUT TRENDS WILL CONTINUE TO BE MONITORED.

DISCUSSION...SCATTERED THUNDERSTORM DEVELOPMENT IS NOW WELL UNDERWAY
TO THE LEE OF THE LOWER GREAT LAKES.  LOCALLY ENHANCED LOW-LEVEL
CONVERGENCE ALONG THE LAKE BREEZES AND THE SOUTHEASTWARD ADVANCING
COLD FRONT MAY BE CONTRIBUTING TO THIS ACTIVITY...BUT FORCING
ASSOCIATED WITH A FAIRLY VIGOROUS SHORT WAVE IMPULSE PIVOTING
INTO/THROUGH THE LOWER GREAT LAKES REGION MAY BE MORE PROMINENT.

OVERALL...THE ENVIRONMENT DOES NOT APPEAR PARTICULARLY CONDUCIVE TO
SEVERE STORM DEVELOPMENT GIVEN THERMODYNAMIC PROFILES CHARACTERIZED
BY RATHER WEAK TO MODEST LOWER/MID TROPOSPHERIC LAPSE RATES AND
CAPE.  A 40-50 KT SOUTHWESTERLY 500 MB JET STREAK IS CONTRIBUTING TO
STRONG DEEP LAYER SHEAR...BUT LOW-LEVEL FLOW APPEARS RATHER
WEAK...AND LOWER/MID TROPOSPHERIC MEAN FLOW IS PROBABLY GENERALLY
ONLY ON THE ORDER OF 30 KT OR LESS.

STILL...WITH ADDITIONAL BOUNDARY LAYER HEATING AND MIXING LIKELY IN
ADVANCE OF THE COLD FRONT AND ASSOCIATED EVOLVING BROKEN CONVECTIVE
LINE...FURTHER INTENSIFICATION OF STORMS DOES SEEM PROBABLE THROUGH
18-21Z...AS ACTIVITY SPREADS THROUGH THE CHAMPLAIN INTO HUDSON
VALLEYS...TOWARD THE CATSKILLS AND POCONOS...AND ACROSS THE
ALLEGHENY MOUNTAINS/ADJACENT AREAS OF CENTRAL AND SOUTHWESTERN
PENNSYLVANIA.

..KERR/CORFIDI.. 07/21/2015

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

ATTN...WFO...BTV...ALY...PHI...BGM...CTP...PBZ...

LAT...LON   40947840 41757685 42237597 43267440 44237367 44957259
            44687223 42627355 41137534 39957823 40228036 40947840 

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