Quantitative Precipitation Forecast
Issued by NWS

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969
FOUS30 KWBC 190821
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
420 AM EDT MON SEP 19 2016

...VALID 12Z MON SEP 19 2016 - 12Z TUE SEP 20 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 ESE MRH 20 E NCA 15 N OAJ 15 SSW HNZ 15 NNE TDF 20 N LYH
10 SW SHD 30 NE SHD 10 NE RDG POU 10 E CEF 25 SSE PWM 20 SW CWVU.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
65 E NTU 20 NNE FFA 25 E OCW PGV 20 N RWI 15 N AVC 20 SSE CHO
10 E GAI DYL 10 S MMU 15 SW BDR 10 N GON PYM 20 ESE PVC
15 SSW HYA.


A HEAVY TO EXCESSIVE RAINFALL THREAT DEVELOPING MONDAY ALONG AND
TO THE EAST OF A WEAKENING FRONTAL BOUNDARY STRETCHING FROM THE
MID ATLANTIC INTO NEW ENGLAND.  PW VALUES IN THE VICINITY OF THIS
BOUNDARY EXPECTED TO BE MUCH ABOVE AVERAGE..1.75-2.00"+...1.5 TO
2+ STANDARD DEVIATIONS ABOVE THE MEAN.  THIS ALONG WITH FAVORABLE
UPPER DIFFLUENCE FROM THE RIGHT ENTRANCE REGION OF A JET MOVING
ACROSS THE NORTHERN MID ATLANTIC AND UPPER DIFFLUENCE AHEAD OF A
CLOSING OFF UPPER LOW OVER THE SOUTHEAST WILL SUPPORT WIDESPREAD
HEAVY RAINFALL POTENTIAL.  THE SET UP IS SIMILAR TO A PREDECESSOR
RAINFALL EVENT TO THE NORTH OF A LAND FALLING TROPICAL SYSTEM.
TRAINING OR SLOW MOVING OF PRECIPITATION AREAS IN A SOUTHWEST TO
NORTHEASTERLY DIRECTION LIKELY EARLY MONDAY FROM IN THE VICINITY
OF RICHMOND---DC--BALTIMORE---PHL TO NEAR NYC AND ACROSS LONG
ISLAND--WITH THIS POTENTIAL TRAINING AXIS THEN SINKING EAST
SOUTHEASTWARD TOWARD THE COASTAL SECTIONS FROM NORTHEAST
NC---ACROSS NORFOLK--THE SOUTHERN DELMARVA AND COASTAL CENTRAL TO
SOUTHERN NJ MONDAY AFTERNOON/EVENING.  OVERALL--THERE IS A STRONG
SIGNAL IN THE LATEST GUIDANCE FOR THE HEAVY TO EXCESSIVE RAINFALL
THREAT---WITH DIFFERENCES PRIMARILY WITH THE DETAILS OF THE AXIS.
THE HI RES ARW AND NSSL WRF WERE USED PRIMARILY FOR THE QPF AXES
GIVEN HIGHER OVERALL CONFIDENCE WITH THESE MODELS.  AREAL AVERAGE
1-2" AMOUNTS DEPICTED---WITH POTENTIAL FOR ISOLATED TOTALS OF
3-5"+ IN AREAS OF TRAINING.  WHILE FFG VALUES ARE HIGH ACROSS
THESE AREAS GIVEN RECENT DRY WEATHER---THE POTENTIAL FOR
TRAINING---ESPECIALLY IN URBAN AREAS---WILL POSE A THREAT OF
EXCESSIVE RAINFALL AMOUNTS.


ORAVEC
$$





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