Graphic for MPD #0448

MESOSCALE PRECIPITATION DISCUSSION 0448
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
554 AM EDT THU JUL 06 2017

AREAS AFFECTED...FAR SOUTHERN PA...NORTHERN/EASTERN
VA...CENTRAL/SOUTHERN MD

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 060950Z - 061500Z

SUMMARY...SLOW-MOVING SHOWERS AND THUNDERSTORMS WITH INTENSE
RAINFALL RATES ARE EXPECTED THIS MORNING...WITH LOCALLY
SIGNIFICANT IMPACTS TO THE MORNING RUSH HOUR. SOME FLASH FLOODING
IS LIKELY.

DISCUSSION...THE LATEST EXPERIMENTAL GOES-16 10.3 MICRON/IR
IMAGERY SHOWS A CLUSTER OF GRADUALLY COOLING CLOUD TOPS IN
ASSOCIATION WITH AN ORGANIZING AXIS OF HEAVY SHOWERS AND FEW
EMBEDDED THUNDERSTORMS STRETCHING FROM NEAR THE NORTHERN NECK OF
VA NORTHWARD TO THE WESTERN AND SOUTHERN SUBURBS OF WASHINGTON
D.C.

THE ACTIVITY IS EXPANDING WITHIN A VERY MOIST AND MODESTLY
UNSTABLE ENVIRONMENT OUT AHEAD A SMALL SCALE SHORTWAVE TROUGH
EJECTING EAST ACROSS THE WV PANHANDLE EARLY THIS MORNING. THE
PWATS ARE ON THE ORDER OF 2 INCHES...AND WITH COOLING CONVECTIVE
TOPS...THE RAINFALL RATES ARE LIKELY TO BE QUITE INTENSE AND
POTENTIALLY AS HIGH AS 2.5 INCHES/HR GIVEN THE HIGHLY EFFICIENT
RAINFALL PROCESSES THAT ARE LIKELY TO BE IN PLACE.

THE LAST SEVERAL HRRR RUNS HAVE BEEN INSISTENT ON AN AXIS OF VERY
RAINFALL IMPACTING THE WASHINGTON D.C. METROPOLITAN AREA AND
ADJACENT SUBURBS FOR THE MORNING RUSH HOUR...AND IN TIME EXTENDING
FARTHER NORTH UP ACROSS CENTRAL MD AND POSSIBLY FAR SOUTHERN PA
TOWARD LATE MORNING.

THE INTENSE RAINFALL RATES AND SLOW CELL MOTION WILL ENCOURAGE
ENHANCED RAINFALL TOTALS...WITH AMOUNTS THROUGH LATE-MORNING
REACHING AS HIGH AS 3 TO 4 INCHES IN SOME AREAS WITH ISOLATED
HEAVIER AMOUNTS WHERE STRONGER CONVECTIVE CORES SET UP.

GIVEN THE INTENSE RAINFALL RATES AND URBANIZED ENVIRONMENT THAT
THE HEAVY RAINFALL WILL BE IMPACTING...SOME FLASH FLOODING WILL BE
LIKELY...AND THUS SIGNIFICANT IMPACTS TO THE MORNING RUSH HOUR
WILL BE EXPECTED. WILL CONTINUE TO MONITOR.

ORRISON

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

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

LAT...LON   39937693 39587628 38507633 37667603 37147629
            37417693 37957722 38957794 39437791 39847758
           


Last Updated: 554 AM EDT THU JUL 06 2017