MESOSCALE PRECIPITATION DISCUSSION 0215
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 PM EDT MON MAY 28 2018

AREAS AFFECTED...CENTRAL/SOUTHERN WV...CENTRAL/SOUTHERN VA

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

VALID 281755Z - 282355Z

SUMMARY...SCATTERED SLOW-MOVING SHOWERS AND THUNDERSTORMS WITH
VERY HEAVY RAINFALL RATES WILL GRADUALLY EXPAND IN COVERAGE THIS
AFTERNOON. FLASH FLOODING IS POSSIBLE.

DISCUSSION...THE LATEST RADAR IMAGERY IN CONJUNCTION WITH DAYTIME
GOES-16 VISIBLE SATELLITE IMAGERY IS SHOWING THE DEVELOPMENT AND
EXPANSION OF SHOWER AND THUNDERSTORM ACTIVITY OVER THE HIGHER
TERRAIN OF CENTRAL/SOUTHEAST WV AND DOWN ACROSS AREAS OF
WEST-CENTRAL TO SOUTHEAST VA. THE CONVECTION IS FORMING WITHIN A
HIGHLY MOIST AND INCREASINGLY UNSTABLE AIRMASS WHICH IS BEING
FACILITATED BY VERY MOIST AND CONFLUENT LOW LEVEL FLOW FOCUSING
ALONG A FRONTAL ZONE AND ALSO WITH DIURNAL HEATING.

PWATS ACROSS THE REGION ARE GENERALLY BETWEEN 1.75 AND 2
INCHES...WITH MUCAPE VALUES OF 1000 TO 2000 J/KG. GRADUALLY THE
CONVECTION ACROSS THE REGION SHOULD TEND TO BECOME A BIT MORE
SURFACE-BASED AND EXPAND IN COVERAGE AS ADDITIONAL DIURNAL HEATING
TAKES PLACE. THIS WILL ESPECIALLY BE THE CASE OVER THE HIGHER
TERRAIN OF CENTRAL/SOUTHERN WV AND WEST-CENTRAL VA WHERE A BIT
MORE SUN HAS ALREADY BEEN DESTABILIZING THE BOUNDARY LAYER.

EXPECT HEAVY RAINFALL RATES OF UP TO 2 INCHES/HR AND ALSO RATHER
WEAK STEERING CURRENTS THAT WILL PROMOTE SLOW CELL MOTION. THE
LATEST 12Z HIRES MODEL CONSENSUS GOING THROUGH 00Z SUPPORTS AS
MUCH AS 2 TO 4 INCHES OF RAIN WHICH COULD BE A LITTLE CONSERVATIVE
GIVEN THE HIGHLY EFFICIENT MOISTURE ENVIRONMENT AND SLOW CELL
MOTION AND ESPECIALLY WITH OROGRAPHICS AND FRONTAL CONVERGENCE
NEAR BY.

THE ANTECEDENT CONDITIONS ACROSS THE REGION ARE RATHER WET...WITH
LOW FFG VALUES ESPECIALLY NOTED CLOSER TO THE BLUE RIDGE AND
ADJACENT CREST OF THE APPALACHIANS. THEREFORE...EXPECT RUNOFF
CONCERNS AND THE POTENTIAL FLASH FLOODING THIS AFTERNOON AND EARLY
EVENING. WILL CONTINUE TO MONITOR.

ORRISON

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

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

LAT...LON   39088027 39017918 38537843 38217828 37927747
            37447638 36977622 36647682 36717771 37157909
            37388076 37528150 37998210 38448192 38888114