MESOSCALE PRECIPITATION DISCUSSION 0262
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
513 AM EDT SUN JUN 03 2018

AREAS AFFECTED...PORTIONS OF THE MID-ATLANTIC REGION

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

VALID 030912Z - 031500Z

SUMMARY...A FLASH FLOOD THREAT WILL CONTINUE INTO THE LATE MORNING
FOR PORTIONS OF THE MID-ATLANTIC REGION WITH AN ADDITIONAL 2-4
INCHES POSSIBLE BY 15Z. THE FLASH FLOOD THREAT APPEARS TO BE
MAXIMIZED OVER EASTERN VA/SOUTHERN MD...NORTH OF I-64...BUT THE
REGIONAL FLASH FLOOD THREAT SHOULD REMAIN LOCALIZED.

DISCUSSION...AN 850-700 MB LOW CONTINUES TO BE SITUATED OVER THE
EASTERN VA/NC BORDER AS OF 0845Z WITH A SLOW MOVEMENT TOWARD THE
NORTHEAST EXPECTED OVER THE NEXT 6 HOURS. THE HEAVIEST RAINFALL
OVER THE PAST FEW HOURS OCCURRED EAST OF RICHMOND ALONG A SHEAR
AXIS WITH EMBEDDED MESOSCALE CIRCULATIONS AMID ESTIMATED MUCAPE OF
250-750 J/KG. RAIN RATES WERE REPORTED TO BE OVER 2 IN/HR IN NEW
KENT COUNTY BETWEEN 06-07Z WITH PRECIPITABLE WATER VALUES NEAR 2
INCHES. THIS REGION CONTINUES TO EXPERIENCE THE BEST UPPER LEVEL
DIFFLUENCE CONNECTED TO A CLOSED UPPER LEVEL LOW SITUATED OVER
SOUTH-CENTRAL VA AS SEEN IN 6.9 MICRON WATER VAPOR IMAGERY.
FARTHER TO THE NORTHWEST OVER PORTIONS OF THE BLUE RIDGE AND
APPALACHIAN MOUNTAINS...RADAR AND GAUGE REPORTS HAVE SHOWN
RAINFALL RATES APPROACHING 1 IN/HR...AN INCREASE FROM EARLIER IN
THE NIGHT. THE REGION TO THE WEST HAS BEEN IN A REGION OF LOWER
INSTABILITY BUT ENHANCED 850-700 MB CONFLUENT FLOW IN ADDITION TO
WINDS HAVING AN UPSLOPE COMPONENT IN THE LOWER LEVELS.

OVER THE NEXT FEW HOURS...RAP FORECASTS ARE FOR THE CLOSED LOW TO
BEGIN TO OPEN UP WHICH SHOULD REDUCE THE DEGREE OF DIFFLUENCE
ALOFT OVER THE CHESAPEAKE BAY REGION. HOWEVER...ENHANCED RAIN
RATES ALONG THE PIVOTING SHEAR AXIS...FROM PETERSBURG TO
TAPPAHANNOCK AT 0845Z...WILL REMAIN POSSIBLE GIVEN A LINGERING
INSTABILITY MAXIMUM AND HIGHLY ANOMALOUS PRECIPITABLE WATER
VALUES. RAINFALL RATES OF 1-2 IN/HR WILL BE POSSIBLE WITH BRIEF
PERIODS OF TRAINING...MAINLY ALONG THE EASTERN PORTION OF THE
LINGERING SHEAR AXIS.

FARTHER TO THE NORTHWEST FROM CENTRAL VA INTO THE WV PANHANDLE AND
SOUTH-CENTRAL PA...CONFLUENT FLOW WITHIN A LOW LEVEL THETA-E MAX
WILL CONTINUE TO SUPPORT RAINFALL RATES APPROACHING 1
IN/HR...WHICH IS IN EXCESS OF VERY LOW FFG ACROSS NORTHERN VA INTO
THE WV PANHANDLE. WHILE CONFLUENT FLOW IS EXPECTED TO GRADUALLY
WEAKEN THROUGH THE REST OF THE MORNING...ADDITIONAL RAINFALL
ACROSS THIS REGION SHOULD RANGE FROM 1-3 INCHES THROUGH 15Z.

OTTO

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

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

LAT...LON   40627800 40337753 39927742 39037752 38687703
            38817543 38317465 37927490 37837568 37377640
            37157725 37307802 37967872 39297899 40457851