MESOSCALE PRECIPITATION DISCUSSION 0317
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
411 PM EDT SUN JUN 05 2016
 
AREAS AFFECTED...NYC TO PHILADELPHIA PA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 052010Z - 060010Z
 
SUMMARY...A LINE OF CONVECTION IS SHOWING SIGNS OF INCREASING RAIN
RATES AS IT MOVES TOWARDS THE NEW YORK CITY AND PHILADELPHIA PA
METRO AREAS.  HOURLY RAIN RATES UP 2" COULD LEAD TO FLASH FLOODING.

DISCUSSION...A LINE OF THUNDERSTORMS IS SHOWING COOLING CLOUD TOPS
AND INCREASING RAIN RATES AS IT MOVES EASTWARD INTO EASTERN PA. 
IT IS ENTERING A MORE MOIST/UNSTABLE ENVIRONMENT, WHICH APPEARS TO
BE INCREASING PRECIPITATION EFFICIENCY.  PRECIPITABLE WATER VALUES
OF 2" LIE ACROSS THE AREA, 2.5-3 SIGMAS ABOVE THE MEAN FOR EARLY
JUNE.  INFLOW AT 850 HPA IS 30-40 KTS PER VAD WIND PROFILES. 
INSTABILITY HAS BEEN BUILDING ACROSS THE EASTERN SHORE AND NJ PER
TRENDS FROM THE SPC MESOANALYSIS PAGE, WITH DOVER DE REPORTING A
78F DEW POINT AT 20Z.

THE CAM/MESOSCALE GUIDANCE SHOW A GENERAL SIGNAL FOR LOCAL AMOUNTS
OF 2-3", WHICH COULD FALL QUICKLY.  HOURLY RAIN RATES COULD REACH
2" AN HOUR DUE TO CELL MERGERS OR WHERE MESOSCALE WAVES FORM ALONG
THE SQUALL LINE, WHICH HAVE BEEN APPARENT IN RECENT RADAR IMAGERY.
 THERE IS A CHANCE THAT THE INVADING LINE COULD SLOW DOWN SOMEWHAT
AS IT MOVES INTO THE MORE UNSTABLE ENVIRONMENT.  ALSO,
THUNDERSTORMS COULD INCREASE IN NUMBER ALONG THE TEMPERATURE/DEW
POINT GRADIENT EXTENDING CURRENTLY INTO SOUTHERN NJ.  THESE RAIN
RATES IN THE URBAN CENTERS BETWEEN NEW YORK CITY AND NEWARK NJ AS
WELL AS PHILADELPHIA PA COULD BE ENOUGH TO CAUSE ISSUES.  FLASH
FLOODING IS POSSIBLE.  

ROTH

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

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

LAT...LON   41457397 41167340 40957332 39957418 39267549 
            39717616 40647584 41447505