Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 161553
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1153 AM EDT Sat Sep 16 2017

.SYNOPSIS...
Weak high pressure will build over our region through Sunday.
Hurricane Jose is forecast to move northward off the mid-
Atlantic coast through mid week, passing near our region Tuesday
into Wednesday. High pressure is expected to once again build
over our region late in the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
The latest visible satellite imagery and surface observations
show the pockets of fog/stratus continue to lift. A noted
increase in cumulus development has occurred over the last hour,
with a few areas of more pronounced development. One of these
is from Mercer County southeastward with another area across
portions of northeastern Pennsylvania (especially higher
elevations). There is still some stratus, which looks to be
lifting some while moving into portions of Monmouth and
northern Ocean counties. The idea is with additional surface
heating this should erode/lift as it tries to advect southwestward.

Our area will remain within a weakening trough aloft and its
associated strung out short wave energy. This along with local
areas of surface convergence may lead to some showers
(especially across eastern Pennsylvania and northern New
Jersey). There is some instability across the area late this
morning and this will continue during the afternoon. While this
might be enough for some thunder, the lack of flow and organized
lift should keep this potential rather low. Any activity may
end up being low-topped, especially if the inversion near 700
mb on the 12z Sterling, VA raob remains.

The hourly temperature, dew point and wind grids were adjusted based
on the latest observations, then the LAMP guidance was blended in
for the next few hours.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
The showers that develop during the day are expected to dissipate
around or after sunset as daytime instability wanes. Once the sun
goes down and the surface temperatures cool, areas of fog and/or
stratus should begin to develop across the area. How thick the fog
becomes is still uncertain at this time, but areas that receive
rainfall today have the greatest threat for the fog to develop.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
The main story remains Hurricane Jose and its pass off our coast
next week.

First on Sunday, we could once again see some isolated to
scattered shower coverage in the afternoon under a weak mid and
upper level low. Temperatures should be similar to what we have
seen the last several days with highs ranging from the lower 70s
to lower 80s.

Monday through Wednesday...Please see the forecast discussion
from the National Hurricane Center for the latest details on the
forecast track of Hurricane Jose. For our area, we are still
looking at a track with the center passing several miles off
shore, though still close enough for impacts to our region. At
this point, we are expecting most of the impacts on Tuesday,
though it should be noted there are still large timing
differences between the models. As for the impacts for our
region:

Wind: With the latest track, it appears unlikely, though not
impossible, that our land areas will see winds of tropical
storm force. That being said, Tuesday into Wednesday will be
quite breezy at the shore.

Coastal Flooding: Please see the section below on the potential
for coastal flooding Monday into Tuesday night.

Heavy Rain: Current track keeps the heavy rain off shore on
Tuesday, with our area only seeing the outer rain bands.
However, any additional rain at the shore near or shortly before
a high tide could exacerbate coastal flooding.

Rip currents: Please see the discussion under the marine section
for details on the rip current risk.

Thursday and Friday...Most of the operational models depict a
high amplitude ridge beginning to build over the region through
this period, but it remains uncertain how quickly this will
build. In addition, if it develops far enough north, we could
be in a on shore low level flow regime for our area, tempering
any warming trend due to the increasing thicknesses.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

This afternoon...Cloud bases in the 3,500-4,500 feet range,
however these could lower to around 2,500 feet for a period of
time especially at KABE and KRDG. Some showers (perhaps an
isolated thunderstorm) should develop this afternoon, however
widespread coverage is not expected. Winds light and variable,
becoming locally light from the east to southeast.

Tonight...Any showers end earlier, then some fog and/or stratus
should develop especially initially at KACY and KMIV. There is
less certainty how far inland the stratus gets as it may be more
fog. If less stratus develops, then fog may end up becoming
more widespread with significant visibility restrictions. Winds
light and variable.

Outlook...
Sunday...Once the fog dissipates, should have VFR conditions
through the day. Another round of fog with visibilities of MVFR
or lower is possible Sunday night, but details are uncertain at
this time.

Monday-Tuesday...Expect conditions to deteriorate to MVFR or
lower across most of the region especially Monday night into
Tuesday as Jose passes near our coast. KABE and KRDG may stay
VFR for much of the period as they may be west of the main rain
shield. Breezy easterly winds are possible for much of the
region, with KACY having the highest risk of gusts above 30 KT.

Wednesday...Becoming VFR with decreasing northwest winds.

&&

.MARINE...
Sub-Small Craft Advisory criteria today as seas are forecast to be 3-
4 feet. However, seas are expected to build to 5-6 feet this evening
and remain through the overnight hours. Winds are expected to remain
5-10 knots through tonight. Some fog mainly nearshore should
dissipate today, however then probably redevelop tonight.

Outlook...
Sunday...SCA conditions are expected primarily for seas above 5
feet and primarily for the coastal waters and lower Delaware
Bay.

Monday through Wednesday...Tropical storm conditions will be
possible Tuesday. However, even by Monday morning, winds will be
above SCA criteria in advance of Hurricane Jose approaching from the
south.  Although winds will begin to diminish Wednesday, it will
take time for seas to subside.

Rip Currents...
With 3-4 foot swells of 12-13 seconds today, along with a developing
easterly wind of 5-10 knots, there is a moderate risk for the
development of dangerous rip currents.

A moderate or even high risk is expected through at least mid week
as we continue to see the swells from Hurricane Jose reach our
shores.

&&

.TIDES/COASTAL FLOODING...
Coastal flooding is possible with the high tide cycles Monday
through Tuesday night due to the passage of Hurricane Jose.

A prolonged period of east to northeast winds will allow water to
pile up along the shores. In addition, there is a new moon on
Wednesday, September 20, so astronomical tide levels will be running
high.

Depending on how close Jose tracks to the coast changes how
significant the coastal flooding will be. As of now, minor coastal
flooding is likely with the high tide cycles from Monday afternoon
through Tuesday night. If Jose tracks closer to the coast, then
widespread moderate coastal flooding will become more likely. If the
timing of Jose slows down, then high tide cycles on Wednesday may be
affected as well.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory for hazardous seas from 6 PM this evening
     to 6 PM EDT Sunday for ANZ450>455.

&&

$$
Synopsis...Johnson
Near Term...Gorse
Short Term...Robertson
Long Term...Johnson
Aviation...Gorse/Johnson
Marine...Gorse/Johnson/Robertson
Tides/Coastal Flooding...



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