MESOSCALE PRECIPITATION DISCUSSION 0338
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT THU JUL 09 2015
 
AREAS AFFECTED...PA...SOUTHERN NY/NORTHERN NJ... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 091836Z - 100006Z
 
SUMMARY...CONVECTION AHEAD OF A COLD FRONT IS SLOWLY BECOMING
BETTER ORGANIZED ACROSS CENTRAL PA. LOCALLY HEAVY RAINFALL MAY
EXCEED THE LOW FFG VALUES ACROSS THE REGION. REPEAT CONVECTION IS
LIKELY GIVEN THE UNIDIRECTIONAL WESTERLY FLOW ENCOMPASSING THE
AREA.

DISCUSSION...ALONG THE SOUTHERN PERIPHERY OF THE WESTERLIES...A
FAIRLY STRONG WIND FIELD IS IN PLACE WITH A 0-6 KM MEAN WIND OF
APPROXIMATELY 40 TO 45 KNOTS. THUS...WELL ORGANIZED STORMS ARE
EXPECTED WHICH IS NOW BEING SEEN ON THE VISIBLE SATELLITE IMAGERY.
A BROAD AREA OF CU/TCU IS EVIDENT ACROSS MUCH OF CENTRAL PA WITH
HOURLY RAINFALL RATES CURRENTLY IN THE TENTH TO QUARTER INCH
RANGE. HOWEVER...EXPECT UPDRAFTS TO BECOME BETTER DEFINED AS THEY
FEED OFF SUFFICIENT BUOYANCY CHARACTERIZED BY SURFACE-BASED CAPES
IN THE 1000 TO 2000 J/KG RANGE.

THE FLOW REGIME IN PLACE IS QUITE SUPPORT OF REPEAT CONVECTION
GIVEN UNIDIRECTIONAL WESTERLY FLOW NOTED IN THE 12Z PIT RAOB.
ADDITIONALLY...THE TROPOSPHERE IS QUITE MOIST OVER THE REGION WITH
PWATS IN THE 1.50 TO 1.75 INCH RANGE WITH HIGH FREEZING LEVELS
EXTENDING UP TO APPROXIMATELY 14 KFT. SOME OF THE LOCAL SOUNDINGS
DID SHOW A BIT OF DRY AIR IN THE AIR COLUMN BUT THIS SHOULD
HOPEFULLY ERODE AS FALLING PRECIPITATION MOISTENS THE AIR COLUMN.

EXAMINING THE 12Z CONVECTION-ALLOWING MODELS SUITE...THERE IS A
STRONG SIGNAL SUPPORTING HEAVY RAINFALL ACROSS MUCH OF PA WHILE
EXTENDING INTO SOUTHERN NY. EXPECT MUCH OF THE CONVECTION TO
THRIVE DURING PEAK DIURNAL HEATING WITH SOME ACTIVITY SURVIVING
BEYOND DARK. MODELS SHOW THE SURFACE COLD FRONT WEST OF THE MPD
AREA AS OF 00Z SO EXPECT STRONG SURFACE CONVERGENCE WITH THE FRONT
TO MAINTAIN SOME THUNDERSTORM ACTIVITY BEYOND DUSK.


RUBIN-OSTER

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

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

LAT...LON   42667574 42407464 41617403 40807429 40667611 
            40017755 39887873 40207954 40867954 41717839 
            42207743