MESOSCALE PRECIPITATION DISCUSSION 0110
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
502 AM EDT MON APR 16 2018
AREAS AFFECTED...EAST CENTRAL PA...NORTH CENTRAL MD
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 160900Z - 161400Z
SUMMARY...HEAVY RAINFALL WITH EMBEDDED CONVECTIVE ELEMENTS COULD
RESULT IN A LOCALIZED FLASH FLOOD THREAT ACROSS NORTHERN CENTRAL
MD INTO EAST CENTRAL PA THROUGH THE MID MORNING HOURS.
DISCUSSION...REGIONAL RADARS CONTINUE TO SHOW HEAVY RAINFALL
SURGING NORTHWARD ACROSS CENTRAL AND NORTHERN MD INTO EAST CENTRAL
PA EARLY THIS MORNING. THE BEST INSTABILITY AND LOW LEVEL FORCING
AHEAD OF WARM FRONT STRETCHED ACROSS CENTRAL VA ARE SLOWLY
TRANSLATING EASTWARD ACROSS MD INTO SOUTHEAST PA AND SOUTHWEST
NJ...BUT THE KLWX RADAR LOCAL HOURLY RAINFALL AMOUNTS NEAR 0.75
INCHES OVER NORTH CENTRAL MD.
THUS FAR THIS MORNING...BETWEEN 1.50 AND 2.00 INCHES OF RAINFALL
HAS OCCURRED OVER NORTH CENTRAL MD AND A PORTION OF SOUTH CENTRAL
PA. THE COMBINATION OF LOW LEVEL FORCING (IN THE FORM OF A LOW
LEVEL 50 TO 65 KNOT SOUTH SOUTHEASTERLY JET) AND DYNAMIC FORCING
ASSOCIATED WITH SHORT WAVE ENERGY MOVING INTO CENTRAL VA COULD
COMPENSATE FOR FAIRLY MEAGER INSTABILITY (WITH MUCAPE GENERALLY
BETWEEN 100 AND 250 J/KG OVER NORTH CENTRAL MD AND NEARBY PA) TO
PRODUCE HOURLY RAINFALL RATES BETWEEN 0.50 AND 0.75 INCHES THROUGH
12/13Z OR SO.
THESE RAINFALL RATES COULD RESULT IN LOCAL ADDITIONAL RAINFALL
AMOUNTS OF 1.00/1.50 INCHES THROUGH 14Z. WHILE THESE VALUES ARE
GENERALLY BELOW THE THREE HOUR FLASH FLOOD GUIDANCE VALUES
HERE...LOCALIZED FLASH FLOODING IS POSSIBLE...AS WELL AS FLOODING
IN URBAN AREAS.
THE THREAT FOR LOCALIZED FLASH FLOODING IS EXPECTED TO DIMINISH
AFTER 14Z FROM SOUTH TO NORTH.
HAYES
ATTN...WFO...CTP...LWX...
ATTN...RFC...MARFC...
LAT...LON 40907657 39557629 39117648 38977677 39107707
39507730 39887739 40477751 40807722
Last Updated: 502 AM EDT MON APR 16 2018