MESOSCALE PRECIPITATION DISCUSSION 0340
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
619 PM EDT WED JUN 20 2018

AREAS AFFECTED...CENTRAL APPALACHIANS INTO THE MID ATLANTIC

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

VALID 202218Z - 210318Z

SUMMARY...THIS IS AN UPDATE TO MPD #0337...EXTENDING THE THREAT
REGION FARTHER DOWNSTREAM INTO THE MID ATLANTIC. 

DISCUSSION...CONVECTION CONTINUES TO ENHANCE EARLY THIS EVENING AS
IT PUSHES OUT OF THE CENTRAL APPALACHIANS AND INTO THE MID
ATLANTIC.  THIS ACTIVITY IS FIRING IN THE UNSTABLE
AIRMASS...MUCAPE VALUES 1000+ J/KG AS PER LATEST HRRR...ALONG AND
TO THE WEST OF THE STATIONARY FRONTAL BOUNDARY STRETCHING
NORTHWEST TO SOUTHEAST FROM SOUTHWEST PENNSYLVANIA INTO NORTHERN
TO SOUTHEAST VIRGINIA.  THE 1800 UTC NAM CONEST...ALONG WITH THE
LATEST HRRR AND HRRX SEEM TO HAVE A GOOD DEPICTION COMPARED TO
THEIR SIMULATED RADARS...BUT ARE ALL APPROXIMATELY 2 TO 3 HOURS
TOO SLOW TO PUSH ACTIVITY DOWNSTREAM.

WHILE THIS ACTIVITY DOES APPEAR TO BE ACCELERATING TO THE
SOUTHEAST...CONCERN IS THAT A PORTION OF THE CONVECTIVE LINE MAY
TRAIN AS IT BECOMES ALIGNED TO THE LOW LEVEL WESTERLY FLOW.
PRECIPITATION TOTALS OF 1 TO 1.5"+ PER HOUR POSSIBLE OVER THE NEXT
SEVERAL HOURS.  THIS MAY EXCEED FFG VALUES THAT HAVE LOWERED FROM
HEAVY RAINS THAT HAVE OCCURRED ACROSS THESE AREAS OVER THE PAST 2
DAYS.  THIS MAY BE ESPECIALLY SO IN THE MORE URBANIZED AREAS OF
NORTHERN VIRGINIA INTO DC THAT HAD TRAINING CELLS A FEW DAYS AGO. 

ORAVEC

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

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

LAT...LON   39797965 39727853 39677815 39527757 39477703
            39397666 39187655 39047660 38917656 38557620
            38337611 37807586 37587585 37067562 36727575
            36517585 36387610 36437647 36577696 36647731
            37317753 37587783 37837843 37897875 38117906
            38347950 38378001 38328050 38388091 38448131
            38778159 39318133 39568093 39678066