MESOSCALE PRECIPITATION DISCUSSION 0261
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1205 AM EDT SUN JUN 03 2018

AREAS AFFECTED...SERN PA...NRN DE INTO MD/D.C. AND CNTRL/ERN VA

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

VALID 030404Z - 030910Z

SUMMARY...ADDITIONAL FLASH FLOODING WILL BE POSSIBLE ACROSS
PORTIONS OF THE NORTHERN MID-ATLANTIC REGION OVER THE NEXT FEW
HOURS.  AN ADDITIONAL 2-4 INCHES WILL BE POSSIBLE IN A FEW
LOCATIONS ON TOP OF SATURATED SOILS.

DISCUSSION...03Z VAD WIND PLOTS DEPICTED A NEARLY STATIONARY
850-700 MB LOW ALONG THE EASTERN VA/NC BORDER. LOOPS OF REGIONAL
RADAR IMAGERY HELPED IDENTIFY SEVERAL MESOSCALE
CIRCULATIONS...WITH ONE MORE PROMINENTLY LOCATED OVER SOUTHERN
KING WILLIAM COUNTY...CO-LOCATED WITH SOME OF THE STRONGEST 850 MB
FLOW TO ITS NORTH (20-25 KT) AND WITH THE HEAVIEST RAINFALL
OCCURRING REGIONALLY AS OF 0330Z. RADAR AND GROUND TRUTH SHOWED
1-2 IN/HR RAINFALL RATES OCCURRING WITHIN THIS AREA OF HEAVIER
RAINFALL SITUATED BETWEEN RICHMOND AND THE POTOMAC RIVER THROUGH
0330Z. SOME OF THE BEST UPPER LEVEL DIFFLUENCE WAS LOCATED OVER
THIS REGION ALONG WITH THE GREATEST MAGNITUDE OF LINGERING MLCAPE
OF ROUGHLY 500 J/KG PER THE LATEST SPC MESOANALYSIS PAGE.

WHILE A BROAD RISK FOR FLASH FLOODING IS HIGHLIGHTED IN THIS
MPD...THE TWO AREAS OF GREATEST CONCERN ARE ACROSS THE VIRGINIA
TIDEWATER REGION AND THE BLUE RIDGE MOUNTAINS OF CENTRAL AND
NORTHERN VIRGINIA. GIVEN LITTLE FORECAST MOVEMENT OF THE 850-700
MB LOW OVER THE NEXT FEW HOURS...THE STRONGEST 850 MB FLOW WILL
CONTINUE TO RESIDE FROM THE CHESAPEAKE BAY INTO CENTRAL VA WHICH
IS WHERE FORECAST UPWIND CORFIDI VECTORS ARE OF THE GREATEST
MAGNITUDE...OPPOSITE TO THE EASTERLY 850 MB FLOW...PROMOTING
TRAINING POTENTIAL. UNTIL CAPE IS EXHAUSTED...PORTIONS OF EASTERN
VIRGINIA WILL CONTINUE TO SEE RAINFALL RATES OF 1-2 IN/HR WITH
SLOW MOVEMENT TO THE RAINFALL CORES.

FARTHER WEST...AN UPSLOPE COMPONENT INTO THE BLUE RIDGE MOUNTAINS
HAS BEEN CONSISTENTLY HIGHLIGHTED IN THE HOURLY UPDATING
EXPERIMENTAL NSSL NEWS-E MODEL...WITH GREATER THAN 90 PERCENT
PROBABILITIES OF EXCEEDING 2 INCHES ACROSS THE BLUE RIDGE THROUGH
08Z. GIVEN WET ANTECEDENT CONDITIONS OVER THE PAST FEW
WEEKS...FLASH FLOOD GUIDANCE IS LOW AND ANY OVERLAP ON TOP OF
HEAVIER RAINFALL FROM THE PAST 24 HOURS WILL GENERATE POSSIBLE
FLASH FLOODING. 2-4 INCH TOTALS APPEAR REASONABLE IN A FEW
LOCATIONS THROUGH 09Z AND ARE CONSISTENT WITH RECENT HRRR AND
EXPERIMENTAL HRRR RUNS.

OTTO

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

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

LAT...LON   40087678 40087633 40037581 39877556 39397550
            38717583 38027585 37477578 37017573 36667608
            36777706 37197820 37727880 38087884 39007838
            39657783 39977741