MESOSCALE PRECIPITATION DISCUSSION 0283
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
700 PM EDT TUE JUN 30 2015
 
AREAS AFFECTED......EASTERN PA...NORTHERN NJ...SOUTHERN NY
STATE... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 302300Z - 010400Z
 
SUMMARY...CONVECTION DEVELOPING ALONG AND NORTH OF A QUASI
STATIONARY BOUNDARY EXTENDING ACROSS EASTERN PA AND NORTHERN NJ
COULD RESULT IN LOCALIZED FLASH FLOODING.

DISCUSSION...CONVECTION CONTINUES TO REDEVELOP ALONG AND NORTH OF
A QUASI STATIONARY EXTENDING FROM SOUTH CENTRAL PA INTO NORTHWEST
NJ. MLCAPE VALUES RANGE BETWEEN 500 AND 1000 J/KG ALONG THE
FRONT...WHICH IS JUST EAST OF A 1.60 INCH PRECIPITABLE WATER AXIS
STRETCHING ALONG THE INTERSTATE 95 CORRIDOR. THE LATEST WATER
VAPOR LOOP SHOWS A SHORT WAVE APPROACHING FROM CENTRAL
PA...PROVIDING SYNOPTIC SCALE ASCENT FOR CONTINUED REDEVELOPMENT
OF CONVECTION THROUGH THE EVENING HOURS. 

THE LATEST RAP SHOWED A 20 TO 30 KNOT LOW LEVEL SOUTHERLY FLOW
TRANSPORTING MOISTURE AND INSTABILITY UP ALONG AND OVER THE FRONT
THROUGH THE LATE EVENING. THE CONSENSUS OF HIGH RESOLUTION MODELS
(INCLUDING THE LATEST RAP...12Z ARW/NMMB AND 12Z SSEO MEAN) SHOWED
AN AXIS OF RAINFALL EXTENDING ACROSS PORTIONS OF EASTERN PA AND
NORTHERN NJ THROUGH 04Z...WITH LOCAL 1-2 INCH AMOUNTS POSSIBLE. AS
WAS THE CASE THIS AFTERNOON...INSTABILITY COULD BE THE LIMITING
FACTOR FOR CONVECTION ACROSS PORTIONS OF SOUTHERN NY STATE...AND
THE HIGHEST CONFIDENCE FOR ADDITIONAL FLASH FLOODING LIES ACROSS
EASTERN PA AND NORTHERN NJ.

ONE AND THREE HOUR FLASH FLOOD GUIDANCE VALUES OVER THIS REGION
ARE AS LOW AS AN INCH...AND EARLIER HEAVY RAIN HAS YIELDED
SATURATED SOILS. ADDITIONAL CONVECTION COULD RESULT IN FLASH
FLOODING.

HAYES 

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

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

LAT...LON   42177497 41977410 41707391 41297389 41067402 
            40867423 40787433 40757439 40257500 39967636 
            40537682 40737672 40727676 41587604