MESOSCALE PRECIPITATION DISCUSSION 0444
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
136 PM EDT SAT JUL 09 2016
 
AREAS AFFECTED...CENTRAL/EASTERN NY...VT...FAR WESTERN MA...FAR
WESTERN CT...NJ...EASTERN PA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 091735Z - 092335Z
 
SUMMARY...THUNDERSTORMS WITH HEAVY RAINFALL WILL EXPAND IN
COVERAGE THIS AFTERNOON. SOME FLASH FLOODING IS POSSIBLE.

DISCUSSION...A MID LEVEL TROUGH ADVANCING TOWARD THE ST LAWRENCE
RIVER VALLEY IS FOSTERING LOW PRESSURE OVER NORTHERN NY EARLY THIS
AFTERNOON WITH A TRAILING COLD FRONT EXTENDING SOUTHWEST IN
WESTERN PA. MEANWHILE...A WAVY STATIONARY FRONT IS NOTED OVER
EASTERN NY AND EXTENDING SOUTH INTO EASTERN PA AND THE DELMARVA.
THE AIRMASS OVER SOUTHERN NEW ENGLAND AND DOWN INTO COASTAL AREAS
OF THE NORTHERN MID-ATLANTIC IS QUITE STABLE GIVEN PRESENCE OF A
MARINE LAYER WHICH IS FAIRLY WELL-ENTRENCHED AS EVIDENCE BY LOW
LEVEL EASTERLY FLOW AND LOW CLOUDS. HOWEVER...THE HIRES GUIDANCE
INCLUDING THE HRRR AND HRRRP SUGGEST A GRADUAL EROSION OF SOME OF
THIS STABLE AIR THROUGH THE AFTERNOON AND A RETREAT OF THE FRONT
BACK TO THE NORTHEAST AHEAD OF THE LARGER SCALE TROUGHING MOVING
INTO THE NORTHEAST.

CONVECTION IS ALREADY INITIATING AND EXPANDING IN COVERAGE OVER
PORTIONS OF CENTRAL/EASTERN NY AND VT WHERE IT IS MORE UNSTABLE
AND THERE IS STRONGER FORCING ALOFT WITH AID OF BETTER JET
DYNAMICS. OVER THE NEXT SEVERAL HOURS...THE TRENDS SHOULD BE FOR A
GRADUAL DESTABILIZATION OF THE BOUNDARY LAYER FROM SOUTHEAST NY
DOWN INTO EASTERN PA AND AT LEAST WESTERN PORTIONS OF NJ. THIS
SHOULD HELP ALLOW CONVECTION TO DEVELOP AND EXPAND IN COVERAGE
THROUGH THE AFTERNOON. LARGER SCALE FORCING FROM THE APPROACHING
MID LEVEL TROUGH COUPLED WITH LOW LEVEL FRONTAL CONVERGENCE SHOULD
TEND TO HELP CONCENTRATE AND FOCUS SOME OF THE CONVECTION. PWATS
ARE GENERALLY IN THE 1.5 TO 1.8 INCH RANGE...AND THIS AGAIN WILL
FACILITATE HEAVIER RAINFALL RATES.

EXPECT AS MUCH AS 3 TO 4 INCHES OF RAIN THIS AFTERNOON WITHIN SOME
OF THE MORE ORGANIZED CONVECTIVE CLUSTERS AND AREAS OF POTENTIAL
TRAINING LINE SEGMENTS. THIS MAY RESULT IN SOME FLASH FLOODING.

ORRISON

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

ATTN...RFC...MARFC...NERFC...

LAT...LON   45047281 44497217 42957248 41727308 39897411 
            39537464 39707558 40387613 41397602 42577558 
            43587515 44837422