Graphic for MPD #0389

MESOSCALE PRECIPITATION DISCUSSION 0389
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 AM EDT SAT JUN 24 2017

AREAS AFFECTED...NORTHERN MID-ATLANTIC STATES

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

VALID 240546Z - 241146Z

SUMMARY...CONVECTION HAS BEEN SLOWLY DEVELOPING ACROSS SOUTHERN
PA.  WITHIN A VERY WARM AND MOIST AIRMASS, HOURLY RAIN RATES TO
1.5" WITH LOCAL AMOUNTS TO 3" ARE EXPECTED.

DISCUSSION...ELEVATED WARM-TOPPED CONVECTION HAS BEEN DEVELOPING
TO THE EAST OF POST-TROPICAL CYCLONE CINDY ACROSS SOUTHERN PA AS
OF LATE.  PRECIPITABLE WATER VALUES ARE ~2".  INFLOW AT 850 HPA IS
WEST-SOUTHWEST AT 40-50 KTS PER VAD WIND PROFILES.  EFFECTIVE BULK
SHEAR IS ALSO NEAR 50 KTS, WHICH ALONG WITH FAIRLY UNIDIRECTIONAL
FLOW WITH HEIGHT IS ORGANIZING THE ACTIVITY INTO A BAND.  THIS IS
IMPORTING MUCAPE VALUES OF 500-1000+ J/KG FROM NORTHERN
VA/MD/SOUTHERN NY OVER THE BOUNDARY.  HOURLY RAIN RATES ACROSS
SOUTH-CENTRAL PA JUST EXCEEDING 1" PER RADAR ESTIMATES AND SLOWLY
RISING.

THE MESOSCALE GUIDANCE IS IN GOOD AGREEMENT ON THE AXIS, WHICH
APPEARS CLOSE TO RECENT RADAR IMAGERY, AND FOR LOCAL AMOUNTS OF
2-3".  BECAUSE THE LOW-LEVEL FLOW IS SOMEWHAT PARALLEL TO THE
INSTABILITY ISOPLETHS, BELIEVE THE CAP ON HOURLY RAIN RATES IS
~1.5".  THIS COULD EXCEED THE FLASH FLOOD GUIDANCE VALUES ACROSS
PORTIONS OF THIS REGION, PARTICULARLY URBAN AREAS.

ROTH

ATTN...WFO...ALY...BGM...CTP...LWX...OKX...PHI...

ATTN...RFC...MARFC...NERFC...

LAT...LON   41527388 41237186 40357419 39397822 40277728
           


Last Updated: 147 AM EDT SAT JUN 24 2017