MESOSCALE PRECIPITATION DISCUSSION 0104
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
405 PM EDT SUN APR 15 2018

AREAS AFFECTED...PORTIONS OF WRN VA...ERN WV AND FAR SWRN PA

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

VALID 152004Z - 160130Z

SUMMARY...FLASH FLOODING MAY DEVELOP OVER PORTIONS OF ERN WV...WRN
VA INTO FAR SWRN PA THROUGH THE REMAINDER OF THE AFTERNOON INTO
THE EVENING. RAINFALL RATES OF 1-1.5 IN/HR COULD LEAD TO 2-4 INCH
TOTALS ON A LOCALIZED BASIS ACROSS AN AREA WITH LOW FFG.

DISCUSSION...REGIONAL RADAR THROUGH 1930Z SHOWED THE EWD MOVEMENT
OF A QLCS ACROSS THE CAROLINAS WITH A WEAKENED CONVECTIVE LINE TO
THE NORTH...EXTENDING INTO WRN VA AND CNTRL WV. TRENDS IN MUCAPE
VIA THE SPC MESOANALYSIS PAGE SHOWED SUBTLE INCREASES OVER THE
PAST COUPLE OF HOURS WITH AN ESTIMATED 100-500 J/KG OVER THE
APPALACHIANS AS OF 19Z WITH LOCALLY HIGHER VALUES EAST OF THE BLUE
RIDGE INTO THE PIEDMONT. WATER VAPOR IMAGERY OVER THE MID-ATLANTIC
REGION SHOWED A DIFFLUENT FLOW PATTERN ALOFT WITH RAP ANALYSES
INDICATING A 110-130+ KT JET CORE EXTENDING FROM ERN KY INTO LOWER
MICHIGAN...PLACING THE RIGHT ENTRANCE REGION AND ENHANCED UPPER
DIVERGENCE OVER THE CNTRL APPALACHIANS.

WHILE THE NARROW NORTH-SOUTH AXIS OF HEAVY RAIN CONTINUES TO
SLOWLY MOVE EAST ACROSS SWRN VA AT 15-25 KT...WITH EMBEDDED
RAINFALL RATES OF 1 TO 1.5 IN/HR...FFG VALUES AHEAD OF THE
NORTHERN END OF THE CONVECTIVE LINE ARE ONLY 1.5 TO 2.5 INCHES IN
3 HOURS. FORECASTS OF 850 MB FLOW OVER ERN WV INTO WRN VA SUPPORT
40-50 KT OVER THE NEXT 3-6 HOURS FROM THE SSE...WITH TERRAIN
INFLUENCES A CONSIDERATION. INCREASES IN UPPER SUPPORT AS AN UPPER
TROUGH AXIS BECOMES MORE NEGATIVELY TILTED MAY SUPPORT BRIEF
INCREASES IN RAINFALL RATES TO THE NORTH...DESPITE WEAK
INSTABILITY...WHICH COULD POSE FLASH FLOODING IN A FEW LOCATIONS
GIVEN THE LOW FFG. AN ADDITIONAL 2-4 INCHES THROUGH 02Z WILL BE
POSSIBLE ON A LOCALIZED BASIS.

OTTO

ATTN...WFO...CTP...LWX...PBZ...RAH...RLX...RNK...

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

LAT...LON   39968036 39967977 39837939 39587907 39137871
            38527826 38027854 37617883 37267912 36817932
            36507944 36197969 36128001 36208037 36398073
            36818089 37408096 37928086 38688067 39178062
            39578048