MESOSCALE PRECIPITATION DISCUSSION 0529
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
121 AM EDT TUE JUL 24 2018

AREAS AFFECTED...CAROLINAS INTO THE MID-ATLANTIC STATES

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

VALID 240520Z - 241120Z

SUMMARY...SHOWERS AND THUNDERSTORMS ARE INCREASING ACROSS THE
CAROLINAS AND MID-ATLANTIC STATES.  HOURLY TOTALS TO 2" WITH LOCAL
AMOUNTS TO 4" ARE EXPECTED THROUGH 11Z.

DISCUSSION...AN AREA OF SHOWERS AND THUNDERSTORMS IS SHOWING AN
INCREASE IN COVERAGE ACROSS EASTERN SC, EASTERN NC, EASTERN VA,
AND CHESAPEAKE BAY WHILE BANDS OF SHOWERS AND THUNDERSTORMS FESTER
ACROSS EASTERN AND CENTRAL PA.  THE ACTIVITY IS FOCUSED NEAR A
WEAK DEW POINT GRADIENT ACROSS THE REGION WHICH COINCIDES WITH A
RIBBON OF HIGHER PRECIPITABLE WATER VALUES.  PRECIPITABLE WATER
VALUES OF 1.85-2.25" LIE ACROSS THE AREA PER RAP ANALYSIS FIELDS
AND 00Z SOUNDINGS.  INFLOW AT 850 HPA SOUTH-SOUTHEAST AT 20-40 KTS
PER VAD WIND PROFILES, NEAR OR SLIGHTLY EXCEEDING THE MAGNITUDE OF
THE 850-400 HPA WIND.  THIS INFLOW IS PULLING IN ML CAPE VALUES OF
500-1500 J/KG; CIN ACROSS THE REGION APPEARS MINIMAL.  EFFECTIVE
BULK SHEAR OF 25-35 KTS EXISTS PER SPC MESOANALYSES, WHICH
COMBINED WITH NEARLY UNIDIRECTIONAL FLOW WITH HEIGHT IS ALIGNING
THUNDERSTORMS INTO FAIRLY LINEAR BANDS.

OVERALL, THE 00Z NAM CONEST APPEARS TO BE DOING RATHER WELL WITH
THE CONVECTIVE PATTERN, THOUGH MOST OF THE GUIDANCE LEAVES
SOMETHING TO BE DESIRED NEAR THE EASTERN SHORE.  THE GUIDANCE IS
IN GENERAL AGREEMENT THAT CONVECTION ACROSS NORTHEAST SC, NC, VA,
AND MD SHOULD BE ON THE INCREASE OVER THE NEXT SEVERAL HOURS WHILE
CONVECTION ACROSS PA IS EXPECTED TO FLUCTUATE IN INTENSITY AS A
SHORTWAVE NEAR THE WESTERN NY/PA BORDER PULLS AWAY AND CONVECTION
MOVES UP FROM THE SOUTH.  HOURLY RAIN TOTALS TO 2" ARE EXPECTED
GIVEN THE MOISTURE AND INSTABILITY.  THE GUIDANCE HAS A GOOD
SIGNAL FOR LOCALIZED AMOUNTS UP TO 4" IN THIS AREA, WHICH SEEMS
REALISTIC.  GIVEN RECENT RAINS ACROSS THE REGION, ADDITIONAL HEAVY
RAINFALL COULD BE PROBLEMATIC.

ROTH

ATTN...WFO...AKQ...BGM...CAE...CHS...CTP...ILM...LWX...MHX...
PHI...RAH...

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

LAT...LON   42527731 41977621 41617567 40397531 38967529
            37847550 36537592 35197648 33987759 33757797
            33697840 33037903 32777974 33307980 34067992
            35627886 37157766 38367733 39587722