MESOSCALE PRECIPITATION DISCUSSION 0161
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
840 PM EDT THU MAY 17 2018

AREAS AFFECTED...CENTRAL/SOUTHWEST VA...SOUTHEAST WV

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 180040Z - 180600Z

SUMMARY...THE THREAT FOR HEAVY RAIN WILL CONTINUE THIS EVENING.
ADDITIONAL FLASH FLOODING IS LIKELY.

DISCUSSION...LATE-DAY GOES-16 CLEAN IR SATELLITE IMAGERY SHOWS AN
IMPRESSIVELY DIFFLUENT UPPER LEVEL FLOW PATTERN OVER THE
MID-ATLANTIC REGION AS A BROAD UPPER TROUGH MAINTAINS ITSELF OVER
THE SOUTHEAST. THIS COUPLED WITH PROXIMITY OF A STATIONARY
FRONT...DEEP MOISTURE AND AT LEAST MODEST INSTABILITY CONTINUES TO
HELP FOCUS RATHER WIDESPREAD CONVECTION WITH HEAVY RAINFALL.

THE LATEST RADAR IMAGERY CONTINUES TO SHOW THE STRONGEST
CONVECTIVE CELLS ACROSS AREAS OF WEST-CENTRAL TO SOUTHWEST VA
WHERE ALREADY AS MUCH AS 3 TO 4 INCHES OF RAIN HAS FALLEN.
CONVECTIVE CLOUD TOPS ACROSS THIS REGION REMAIN QUITE COLD AND
REFLECTIVE OF WHERE CONVECTION HAS BEEN A BIT MORE CONCENTRATED
THIS AFTERNOON. THE COLD TOPS CONTINUE TO SIGNAL A CONTINUATION OF
ROBUST UPDRAFTS AND THIS IS BEING FACILITATED BY AT LEAST MODEST
INSTABILITY WITH MUCAPE VALUES OF 500 TO 1000 J/KG  POOLED IN
VICINITY OF THE FRONT.

THE ACTIVITY OVER THE NEXT FEW HOURS WILL TEND TO PERSIST A BIT
GIVEN THE AID OF A BROADLY DIFFLUENT UPPER PATTERN AND THE LARGER
SCALE WARM ADVECTION PATTERN. HOWEVER...AS INSTABILITY BECOMES
INCREASINGLY EXHAUSTED...THE RAINFALL RATES SHOULD TEND TO COME
DOWN A BIT. ALSO THE OVERALL COVERAGE SHOULD BEGIN TO COME DOWN.

MUCH OF THE FOCUS SHOULD REMAIN ALONG AND A TAD NORTH OF THE
FRONT...ENCOMPASSING AREAS FROM CENTRAL AND SOUTHWEST VA WEST TO
SOUTHEAST WV. GIVEN PWATS OF 1.75 INCHES OR GREATER...THE RAINFALL
RATES SHOULD STILL BE CAPABLE OF REACHING AS MUCH AS 2 INCHES/HR
WITHIN THE STRONGER CONVECTIVE CORES. THE LATEST HRRR GUIDANCE
TENDS TO SUPPORT THE GREATEST CONCENTRATION OF RAINFALL PERSISTING
OVER AREAS OF WEST-CENTRAL AND SOUTHWEST VA AND ALSO GETTING INTO
PARTS OF FAR SOUTHEAST WV.

EXPECT AS MUCH AS AN ADDITIONAL 3 TO 4 INCHES TO BE POSSIBLE AT
LEAST LOCALLY. THESE VALUES WILL CONTRIBUTE TO ADDITIONAL FLASH
FLOODING CONCERNS THROUGH THE EVENING HOURS.

ORRISON

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

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

LAT...LON   38267832 38247742 38167680 37987653 37677641
            37307669 37087739 36997827 36957948 37048031
            37168098 37408127 37788125 38088063 38247951