MESOSCALE PRECIPITATION DISCUSSION 0288
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1113 PM EDT SUN JUN 10 2018

AREAS AFFECTED...SE PENNSYLVANIA...S/C NEW JERSEY

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

VALID 110312Z - 110900Z

SUMMARY...A HEAVY RAIN BAND WILL SLOWLY PIVOT ACROSS SOUTHEAST
PENNSYLVANIA AND SOUTHERN AND CENTRAL NEW JERSEY TONIGHT...WITH
SEVERAL INCHES OF RAIN LIKELY IN SOME AREAS. THIS INCLUDES THE
PHILADELPHIA METRO AREA. THE RAIN RATES COULD BRIEFLY REACH 1
IN/HR IN THE HEAVIER PORTIONS OF THE RAIN BAND. THIS HEAVY
RAINFALL COULD LEAD TO AREAS OF FLOODING.

DISCUSSION...MRMS COMPOSITE RADAR AND KDIX AND KCCX RADAR
REFLECTIVITY HIGHLIGHT A PROMINENT BAND OF MODERATE TO HEAVY RAIN
FROM CENTRAL PENNSYLVANIA THROUGH CENTRAL NEW JERSEY...AT 03Z
ROUGHLY FROM 15SE KUNV TO KMUI TO KLOM TO KMJX. THE BAND OF HEAVY
RAIN WAS CHARACTERIZED BY DOMINANT COLLISION-COALESCENCE PROCESSES
WITH MRMS VERTICALLY INTEGRATED ICE (VII) SHOWING HARDLY ANY
POSITIVE VALUES AND RADAR REFLECTIVITY EXTREMELY LIMITED ABOVE THE
-10C LAYER. THIS IS EXPECTED TO CONTINUE THROUGH THE OVERNIGHT
HOURS WITH LIMITED INSTABILITY. THE RAIN BAND SHOULD BE
PREDOMINATELY FORCED THROUGH AN INCREASING FRONTOGENETIC
CIRCULATION IN THE LOW LEVELS...AND ITS CURRENT POSITION ROUGHLY
COINCIDED WITH THE 925-850MB FGEN MAX. PRECIPITABLE WATER VALUES
IN THE SAME REGION WERE AROUND 1.5 INCHES PER THE CIRA BLENDED TPW
PRODUCT. RELATIVE TO THE OVERALL CLIMATOLOGY THIS IS NOT
EXCEPTIONALLY HIGH...BUT RELATIVE TO THE LOWER 1000-500MB
THICKNESSES (560-565 DKM) TO THE NORTH OF A SYNOPTIC SURFACE FRONT
IT IS QUITE HIGH...INDICATIVE OF A DEEP SATURATED PROFILE THAT IS
MORE THAN SUPPORTIVE OF HEAVY RAINFALL. THE COMBINATION OF HIGH
PWATS...STRONG FORCING...AND DOMINANT WARM RAIN PROCESSES SHOULD
LEAD TO VERY EFFICIENT RAINFALL.

THE 00Z HI-RES MODELS UNANIMOUSLY SHOW A BAND OF HEAVY RAINFALL
FROM SE PA INTO NJ...WITH SEVERAL INCHES OF RAIN POSSIBLE GIVEN
THE SLOW PIVOTING NATURE OF THE RAIN BAND. THIS COULD CREATE SOME
AREAS OF FLOODING...PARTICULARLY IN URBAN AREAS. BOTH DUAL POL
RADAR AND MRMS RAINFALL ESTIMATES AND A FEW LOCAL OBSERVATIONS IN
SE PA HAVE SHOWN RAIN RATES TO REACH 1 IN/HR IN SOME PORTIONS OF
THE RAIN BAND ALREADY...AND THIS IS LIKELY TO CONTINUE. FLASH
FLOODING WOULD BE POSSIBLE IF THOSE RATES COULD BE SUSTAINED FOR A
COUPLE HOURS.

LAMERS

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

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

LAT...LON   40857688 40767602 40427478 40117394 39707379
            39187452 39467546 39937658 40527747