MESOSCALE PRECIPITATION DISCUSSION 0307
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 PM EDT THU AUG 21 2014
 
AREAS AFFECTED...EASTERN PA...CENTRAL AND NORTHERN NJ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 220245Z - 220600Z
 
SUMMARY...REPEATING SHOWERS AND THUNDERSTORMS SHOULD CONTINUE THE
NEXT FEW HOURS AND WILL FOSTER A CONCERN FOR FLASH FLOODING.

DISCUSSION...THE LATEST WV IMAGERY SHOWS A COMPACT UPR LOW
DROPPING SEWD ACROSS NY ATTM...AND IS PROVIDING A DYNAMICALLY
FAVORABLE ENVIRONMENT FOR CONVECTION DESPITE MODEST INSTABILITY
PROFILES.

IR SAT IMAGERY INDICATES REPEATING CLUSTERS OF WARM-TOPPED
CONVECTION OVER NERN PA AND SWD DOWN ALONG THE PA/NJ BORDER. GIVEN
HOW DIV THE FLOW ALOFT IS AND WITH SOME UPSLOPE FLOW COMPONENT
OVER THE HIGHER TERRAIN...IT APPEARS LIKELY THAT THE ONGOING
CONVECTION WILL BE ABLE TO PERSIST AND UTILIZE THE MODEST AMT OF
INSTABILITY THAT IS IN PLACE.

CONVECTION SHOULD CONTINUE TO FOCUS IN PARTICULAR OVER THE POCONOS
AND ADJACENT FOOTHILLS THROUGH AT LEAST ABOUT 06Z. THE ACTIVITY
WILL LIKELY TEND TO DEVELOP A BIT FARTHER SOUTH DOWN ALONG THE
EXISTING INSTABILITY GRADIENT. THERE IS A MARINE LAYER THAT HAS
PUSHED WEST IN OFF THE ATLANTIC OCEAN OVER A LARGE PORTION OF NJ
AND SO THE CONVECTION WILL LIKELY HAVE A VERY DIFFICULT TIME
SUSTAINING ITSELF TOO FAR EAST THROUGH NJ...BUT GIVEN HOW STRONG
THE DYNAMICS ALOFT ARE...SOME WEAKER CELLS ARE LIKELY TO MOVE SEWD.

RAINFALL RATES OF 1 TO 2 INCHES/HR ARE EXPECTED TO PERSIST WITH
LOCALLY HIGHER AMTS OVER HIGHER TERRAIN. GIVEN THE REPEATING
NATURE...FLASH FLOODING IS LIKELY AT LEAST LOCALLY.

ORRISON

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

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

LAT...LON   40107509 40657570 41237580 41457487 40627398 40157399
            39947446 40107509