MESOSCALE PRECIPITATION DISCUSSION 545
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
556 PM EDT SUN JUL 23 2017

AREAS AFFECTED...N MARYLAND...SE PENNSYLVANIA...DELAWARE...S NEW
JERSEY

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 232156Z - 240156Z

SUMMARY...RAINFALL RATES OF 1-2 IN/HR WITH PERIODS OF TRAINING
WILL POSE A FLASH FLOOD THREAT FROM SE PENNSYLVANIA AND NORTH
CENTRAL MARYLAND EASTWARD TO THE JERSEY SHORE THROUGH 02Z. 
ISOLATED 3 TO 4 INCH RAINFALL TOTALS WILL BE POSSIBLE FOR A FEW
LOCATIONS.

DISCUSSION...2130Z REGIONAL RADAR SHOWED MULTIPLE CLUSTERS OF
HEAVY SHOWERS AND THUNDERSTORMS NORTH OF THE GREATER WASHINGTON DC
METRO AREA AND EXTENDING NORTHWARD TOWARDS HARRISBURG PA.  RADAR
ESTIMATES OF 2 INCHES PER HOUR IS CURRENTLY BEING INDICATED.   RAP
ANALYSES AND GPS DATA INDICATE A VERY MOIST AIRMASS WITH PWS ON
THE ORDER OF 1.9 TO 2.3 INCHES ALONG WITH 1000 TO 1500 J/KG OF
MLCAPE.  MULTIPLE CELL MERGERS WITH CONVERGING OUTFLOW BOUNDARIES
WILL LOCALLY ENHANCE CONVECTION AND THUS CAUSE HIGHER RAINFALL
RATES.

RECENT RUNS OF THE HRRR AND HRRR EXPERIMENTAL ARE SUGGESTING THE
POTENTIAL OF 1 TO 3 INCHES OF RAINFALL THROUGH 10PM, WITH A FEW
ISOLATED 4 INCH TOTALS POSSIBLE. THE NAM CONEST AND ARW ALSO
SUPPORT THESE TYPES OF AMOUNTS.  THE GREATEST FLOODING POTENTIAL
EXISTS OVER AREAS THAT HAVE RECEIVED HEAVY RAINFALL EARLIER TODAY.

HAMRICK

ATTN...WFO...CTP...LWX...PHI...

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

LAT...LON   40467657 40447509 40197394 39537402 38877477
            38937558 38997685 39147730 39467754 40097734