Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 260135

Area Forecast Discussion
National Weather Service Mount Holly NJ
935 PM EDT Mon Sep 25 2017

High pressure across our region will gradually lift northeast as it
weakens through midweek. Hurricane Maria will remain offshore the
outer banks of North Carolina through Wednesday, then finally move
out to sea, in advance of a cold front moving through our area on
Thursday. Another fast moving cold front treks through our region on
Friday, followed by a large dome of high pressure settling over our
area early next week.



An area of low clouds and light fog has been moving Wward and
has just came onshore the cntrl an srn NJ and DE shore areas so
far this . These clouds will continue slowly moving westward
overnight and reaching the Philly area for a few hours right
around sunrise. Winds will remain light from the E/SE. Places
the radiated efficiently this evening should fall into the
60`s, with even low 60`s in the southern Poconos.


There will be more clouds and patchy fog across the area Tuesday
morning. The greater concentration will be S/E if I-95 corridor, but
areas N/W of that will still have some fog and low clouds. Guidance
is showing a rather stubborn area of low level moisture remaining
across most areas thru the day. It is therefore difficult to get too
optimistic with regards to how much sun will be over the area Tue.
Mostly cloudy skies S/E and partly sunny N/W will probably describe
the situation best. High temperatures will be only in the low 80s
S/E and mid 80s N/W. Winds will continue to be rather gentle from
the SE or E.


The main forecast challenges will be midweek temperatures, PoPs
Wednesday into Thursday, a clipper-type system over the
weekend, and some uncertainty with the larger scale features by
early next week.

Direct impacts from Hurricane Maria are expected to remain
offshore. Indirect impacts will continue through at least
Thursday, including a high risk for the formation of dangerous
rip currents, high surf, and beach erosion.

We have increased temperatures a couple of degrees on Wednesday,
especially given the low bias exhibited by guidance recently.
This is with the expectation that low clouds will burn off early
in the day. These temperatures may still be a bit conservative,
especially given the low-level temperature profile per model

We have trended a bit drier with the forecast Tuesday night and
focused PoPs Wednesday into Wednesday night, which is in better
agreement with the ensembles, confining chance PoPs to the
coastal plain in the latter time frame.

A drying trend is expected to take hold Thursday and continue
into Friday, with a PoPless forecast at this time. The only
exception may be down the shore on Thursday with the potential
for some lingering showers.

Temperatures slightly above average (~5 degrees) on Thursday are
forecast to trend average to slightly below average into early
next week.

There is some uncertainty with a clipper-type system over the
weekend. Forecast reflects slight chance PoPs across the entire
area on Saturday, when ensembles indicate the greatest chance of
precip, then trending downward by Sunday, with PoPs confined to
the coastal plain.

There is quite a bit of uncertainty early next week with regard
to the large scale features, with a lack of model run to run
consistency. For now, we have not strayed far from the previous
forecast, bringing PoPs in again for Tuesday. But low
confidence at best.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

 Low level onshore flow will continue and this will result in
the arrival of low clouds later tonight and Tuesday. This has
already arrived with a IFR deck at KACY, The clouds will
continue a NW motion. We have tried to time the arrival of the
IFR conditions according to guidance and climatological trends.
There may be some fog developing before the low clouds arrive.
The arrival times will be earlier and departure times later into
Tue morning for the S/E sites. The timing for improvement
Tuesday for all sites is rather low confid attm. Winds thru the
period will be light E or SE.


Tue night and Wed...Low clouds Tue night into Wed morning will
likely result in IFR conditions from the I-95 terminals (TTN-
PNE-PHL-ILG) and points southeast, with greatest confidence in
IFR at ACY and MIV. Cannot rule out some fog as well, but it
looks predominantly like a low cloud issue. Expect improving
conditions to VFR at all terminals Wednesday. Northeast winds
may gust up to 25 knots at times along the coast.

Wednesday night through Friday...Predominantly VFR conditions
expected. Winds shifting to the northwest Wed night and cannot
rule out MVFR in a passing shower into Thursday. Some patchy
fog is possible at the normally more prone locations by
Thursday night.

Saturday and Sunday...Predominantly VFR conditions expected at
this time.



The SCA will continue with the expectation of seas finally
reaching five feet toward sunrise on the coastal waters.
Modeling can be quick in raising seas ahead of strong low
pressure systems. Certainty isn`t as high as ideal for them
rising overnight but another foot or so by sunrise looks doable
based on the trends this evening. Patchy/ares of low clouds and
fog are occurring across the central/southern waters attm and
this will continue overnight and Tuesday. Winds will remain
mostly under 10 knots from the E or SE.


SCA conditions likely to persist over the waters with the
combination of swells from Hurricane Maria and occasional wind
gusts to 25 knots through at least Thursday night. By Friday,
winds and seas are expected to begin subsiding, but there is a
renewed opportunity for SCA conditions over the weekend with
low pressure developing offshore.

Rip Currents...

A HIGH risk for dangerous rip currents is expected for the rest of
tonight through Tuesday.

The rip current risk remains high as long-period southeasterly
swells continue to build thanks to Hurricane Maria. Given the
observed rip currents this weekend along much of the NJ/DE surf
zone, swimming is not recommended, especially in the absence of
lifeguards/beach patrols.

The rip current fatality in Long Branch, NJ on 9/23 brings the
total number to 8 this year - all in NJ. This office has
compiled these statistics since 1998, and this is the greatest
number of fatalities in any one year, followed by 2008 with 6

Dangerous surf conditions will continue for much of the new
week. A HIGH risk for the development of dangerous rip currents
is expected from Tuesday through at least Thursday. High surf
conditions and beach erosion likely to develop Tuesday and


Allentown tied the record high temperature for today of 92
degrees, last set in 1970. Two other sites came within a degree
of their record highs: Philadelphia and Mount Pocono. Here are
the record highs for September 25:

ABE...92(2017 and 1970)
GED...92(2010 and 1970)


NJ...High Rip Current Risk through late Tuesday night for NJZ014-
DE...High Rip Current Risk through late Tuesday night for DEZ004.
MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ452>455.
     Small Craft Advisory for hazardous seas until 6 AM EDT
     Wednesday for ANZ450-451.


Near Term...Gaines/O`Hara
Short Term...O`Hara
Long Term...Franck
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