Quantitative Precipitation Forecast
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259
FOUS30 KWBC 161404
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1002 AM EDT Mon Apr 16 2018

VALID 15Z Mon Apr 16 2018 - 12Z Tue Apr 17 2018


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE MJX 25 ENE ACY 20 SSW MJX 15 N TTN MSV 10 N MSV
30 SW ALB 10 E ALB 10 ESE DDH 15 WNW EEN 15 WNW CON 10 NE LCI
20 E BML 30 WNW WVL 10 ENE WVL 15 E BGR 35 NE BHB 35 W CXGM
35 WSW CXGM 40 ESE BHB 30 SE RKD 55 ESE PSM 25 ESE CQX
15 SSE ACK 20 SSE MTP 30 SSE FRG 20 SE MJX 25 SSE MJX.


Northern Mid-Atlantic states
Portions of New England
~~~~~~~~~~~~~~~~~~~~~~~
A line of heavy showers and embedded thunderstorms within an
atmospheric river/warm conveyor belt stretch from eastern NJ into
southwest New England at 14z/10 am EDT.  The system is composed of
an elongated area of low pressure at the surface and a negatively
tilted mid/upper level trough supporting strong upper level
divergence and 850 hPa inflow of 65 kts per recent VAD wind
profiles from the Upton NY radar.  The upper level shortwave is
expected to broaden/weaken in concert with a weakening upper level
jet with time.  MU CAPE of 100-200 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 persistent 850 hPa moisture transport
axis is expected across portions of southeast NY into adjacent
MA/CT 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/freezing rain.
Rainfall rates will generally not be high enough to exceed 1-3
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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