Quantitative Precipitation Forecast
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332
FOUS30 KWBC 161856
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
255 PM EDT Mon Apr 16 2018

VALID 1855Z Mon Apr 16 2018 - 12Z Tue Apr 17 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 S ACK 15 S MTP 15 SSW IJD 15 S PSF 10 E ALB 15 SW DDH
15 ESE VSF 10 SW IZG 10 W WVL 15 ENE BGR 35 NE BHB 35 W CXGM
35 WSW CXGM 40 ESE BHB 30 SE RKD 55 ESE PSM 25 ESE CQX 25 S ACK.


Portions of New England
~~~~~~~~~~~~~~~~~~~~~~~
A line of heavy showers with embedded thunderstorms within an
atmospheric river/warm conveyor belt stretching across southern
New England at 19z/3 p.m. EDT.  The system is composed of a
strengthening area of low pressure at the surface in eastern
Pennsylvania and a negatively tilted mid/upper level trough
supporting strong upper level divergence and 850 hPa inflow of 70
kts per recent VAD wind profiles from the Norton MA radar.  The
upper level shortwave is expected to broaden/weaken in concert
with a weakening upper level jet with time.  MU CAPE of 100-250
J/kg should allow for continued embedded heavier convective cores
within the broader rain shield, with hourly totals up to 0.75" and
up to around 1.5" in any three hour period remaining possible
given the precipitable water values near 1.5".  A focused and
slightly more persistent 850 mb moisture transport axis is
expected to cross the region which should result in a bit longer
duration of the moderate/heavy rainfall rates, resulting in storm
total amounts at getting into the 2-3" range locally as far north
as eastern NH/ME, where orographic impacts may be maximized in the
strong southerly flow.

Will continue to carry a Marginal risk for these areas, with its
northwest bound defined by wintry precipitation.  Rainfall rates
will generally not be high enough to exceed 1 or 3 hour flash
flood guidance. However, rainfall of the magnitude forecast may
still be enough to cause some urban and small stream flooding
concerns as HRRR-based soil moisture shows significant saturation
in southeast New England.

Roth/Chenard
$$





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