MESOSCALE PRECIPITATION DISCUSSION 0246
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT SUN AUG 03 2014
 
AREAS AFFECTED...SOUTHWESTERN TO SOUTHERN NY/NORTHERN PA... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 031856Z - 040056Z
 
SUMMARY...AN UPPER-LEVEL LOW SPINNING OVER SOUTH-CENTRAL PA WILL
CONTINUE TO IGNITE CONVECTION THIS AFTERNOON. RELATIVELY LOW FFG
VALUES MAY ENHANCE THE THREAT FOR FLASH FLOODING THROUGH ~01Z.
THIS SYSTEM ALREADY HAS A HISTORY OF PRODUCING SUCH CONDITIONS
OVER CENTRAL PA.

DISCUSSION...A BROAD AREA OF LOW-TOPPED PULSE CONVECTION DEVELOPED
EARLIER THIS MORNING WITH THE ACTIVITY EXPANDING IN COVERAGE AS
SURFACE HEATING CONTINUES. CAPE VALUES IN THE REGION ARE 500-1000
J/KG PER THE SPC MESOANALYSIS PAGE.  INFLOW IS MINIMAL INTO THE
REGION, SO INDIVIDUAL STORMS SHOULD BE OUTFLOW-DRIVEN AND
SHORT-LIVED.  HOWEVER...VERY EFFICIENT WARM RAIN PROCESSES ARE IN
PLACE WITH NEARLY SATURATED SOUNDINGS FROM THE SURFACE TO 600-MB,
IMPLYING THAT FORWARD PROPAGATION IS UNLIKELY.  

RAINFALL RATES UP TO 2 INCHES PER HOUR ARE LIKELY WITH POCKETS OF
2-4" AMOUNTS POSSIBLE IN THE STRONGER CONVECTIVE CELLS. SLOW CELL
MOTIONS COMBINED WITH THE MOIST PROFILES SUGGEST FLASH FLOODING
MAY OCCUR IN AREAS OF SOUTHERN NY/NORTHERN PA. HIGH-RESOLUTION
GUIDANCE HAS A PRETTY STRONG HEAVY RAINFALL SIGNAL THROUGH 00Z
WHICH RAISES FORECASTER CONFIDENCE IN THIS SCENARIO -- USED 01Z AS
A HORIZON SINCE THAT HAS WORKED OUT REASONABLY WELL FOR THE WANING
OF CONVECTION THE PAST COUPLE OF DAYS. WILL MAINTAIN A HIGHLIGHTED
AREA THROUGH THE CONVECTIVE CYCLE BEFORE WEAKENING OCCURS BEYOND
~01Z.


RUBIN-OSTER/ROTH

ATTN...WFO...BGM...BUF...CTP...CLE...

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

LAT...LON   42267978 42807932 43117847 43307756 43237611 42817511
            42187490 41817543 41877685 41747841 41717930 42267978