MESO: Nws Weather Prediction Center College Park Md

AWUS01 KWNH 122013
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-122300-

MESOSCALE PRECIPITATION DISCUSSION 0159
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
412 PM EDT FRI JUL 12 2013

AREAS AFFECTED...DE...NERN MD...SERN PA AND SRN/CENTRAL NJ

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

VALID 121937Z - 122300Z

SUMMARY...A CONTINUATION OF MPD #158... AS CONVECTIVELY-INDUCED
CIRCULATION IS DRIFTING UP THE DELMARVA COAST. 1-2 INCH PER HR
RAIN RATES ARE POSSIBLE WITHIN THE HIGHER RADAR REFLECTIVITIES...
FLASH FLOODING AND RUNOFF ISSUES REMAIN PLAUSIBLE.

DISCUSSION...A CONVECTIVE SMALL SCALE VORTICITY MAXIMUM CONTINUES
TO HOVER AND SLOWLY DRIFT UP THE DELMARVA THIS AFTN, WHICH IS
REFLECTED VERY NICELY ON REGIONAL RADAR AND 18Z SURFACE MAP.
RAINFALL RATES FROM THE ELEVATED CONVECTION/OVERRUNNING MOISTURE
ACROSS THE REGION RANGE GENERALLY FROM A .50" TO AN INCH BUT 1-2"
AMOUNTS WITHIN SOME OF THE BETTER INFLOW BANDS. THE MOST
IMPRESSIVE INFLOW NOTCH IS BEING DIRECTED INTO SRN NJ AROUND ACY
AT THE MOMENT AND SPREADING DOWNSTREAM INTO CENTRAL/NRN DE AND
EXTREME NERN MD. 18Z INFLOW IS AROUND 20-25 KNOTS AT 850MB AND
THIS IS ADVECTING IN TROPICAL 2-2.25 INCH PRECIPITABLE WATER
VALUES. TOUGH TO DISCERN HOW MUCH MOVEMENT OR DIRECTION THIS MESO
FEATURE WILL HAVE OVER THE NEXT 3 TO 4 HRS... AS HI-RES GUIDANCE
ADVECTS MOST OF THE MOISTURE WESTWARD WITH TIME... WHILE 12Z
GFS/ECMWF GRADUALLY FILL THE SYSTEM. THE FLASH FLOOD GUIDANCE
REMAINS HIGH, ON THE ORDER OF 2.5 TO 3 INCHES WITHIN AN HR. AS A
RESULT... VERY LOCALIZED AREAS COULD SEE FLASH FLOODING WITH MORE
GENERAL RUNOFF ISSUES ANTICIPATED.

MUSHER

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...CTP...LWX...

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

LAT...LON 38787466 38557529 38897638 39577682 40047673 40427590
40497491 40157393 39417414 38787466

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