MESOSCALE PRECIPITATION DISCUSSION 0202
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
653 PM EDT SAT MAY 26 2018

AREAS AFFECTED...EASTERN WV...CENTRAL VA...CENTRAL MD...DELAWARE

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

VALID 262253Z - 270253Z

SUMMARY...SLOW MOVING SHOWERS AND EMBEDDED THUNDERSTORMS WILL
CONTINUE TO EXPAND EASTWARD TOWARD THE MID ATLANTIC COAST THIS
EVENING. INTENSE HOURLY RAINFALL RATES MAY LEAD TO LOCALIZED FLASH
FLOODING, ESPECIALLY OVER WET SOILS GIVEN ANTECEDENT HEAVY
RAINFALL.

DISCUSSION...AN ONGOING COMPLEX OF SLOW MOVING CONVECTION IS
TAKING FULL ADVANTAGE OF ROBUST DEEP LAYER INSTABILITY (MUCAPES
2000-3000 J/KG) AND DEEP SUBTROPICAL MOISTURE (PW VALUES
1.75-2.00") IN PRODUCING TORRENTIAL SHORT-TERM RAINFALL RATES. UP
TO THIS POINT, THE RELATIVELY LIGHT DEEP-LAYER SHEAR PROFILE HAS
INHIBITED SUSTAINED ORGANIZATION OF STRONGER CLUSTERS (I.E. WITH
PREDOMINATELY PULSE ACTIVITY). HOWEVER, THE UPTICK IN
SOUTHWESTERLY LOW-LEVEL INFLOW AFTER 00Z (25-30+ KTS AT 850 MB PER
THE LATESTS RAP) WILL ALLOW FOR INCREASED UPWIND PROPAGATION THIS
EVENING, AS RECENT RAP RUNS CONTINUE TO DEPICT CORFIDI VECTORS
BECOMING NORTHEAST AROUND 5-10 KTS (INTO THE DIRECTION OF THE
LOW-LEVEL INFLOW).

THE MORE FAVORABLE LOW-LEVEL WIND PROFILE WILL LEAD TO BETTER
ORGANIZATION OF CONVECTIVE CLUSTERS THIS EVENING, ALONG WITH AN
INCREASED POTENTIAL OF BACKBUILDING/TRAINING OF CELLS. NEW
CONVECTIVE DEVELOPMENT AND EXPANSION ALONG AND NEAR THE LEE SIDE
TROUGH, ESPECIALLY WITH COLLIDING OUTFLOW BOUNDARIES, WILL BE
FOSTERED BY THE RICH THERMODYNAMIC ENVIRONMENT AS NOTED ABOVE.

MOST OF THE AVAILABLE HIGH RESOLUTION GUIDANCE (INCLUDING THE MOST
RECENT HRRR AND EXPERIMENTAL HRRR) SUGGEST LOCALIZED TOTALS OF 3+
INCHES THROUGH THE EVENING HORUS, MUCH OF WHICH WOULD FALL IN 2
HOURS OR LESS. GIVEN THE LOWER FFG VALUES OWING TO THE RECENT
HEAVY RAINFALL, RUN-OFF FROM THE STRONGEST CELLS WILL CONTINUE TO
POSE A FLASH FLOOD THREAT.

HURLEY

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

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

LAT...LON   39737660 39617583 39357542 38997510 38467527
            38007580 37327619 36947612 36597655 36587816
            36877887 37137916 37457950 38057977 38917948
            39387900 39717793