Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 162050
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
350 PM EST Thu Nov 16 2017

.SYNOPSIS...
Low pressure will continue to move into the Canadian Maritimes
through Friday, while high pressure briefly builds across the
east coast during Friday. An area of low pressure will move
across the eastern Great Lakes Saturday, then into New England
Saturday night into Sunday. A warm front will lift across the
area Saturday, followed by a strong cold front overnight
Saturday into early Sunday morning. High pressure will build to
our south Monday into Tuesday, before a dry cold front moves
across the area Tuesday night. High pressure then builds in
later Wednesday into Thursday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of mid-afternoon the cold front is rather ill-defined but
estimated over NJ and moving quickly towards offshore. The vort
max aloft is moving into the lower Hudson Valley and the assocd
UVV forcing seems to be out of our forecast area. Both radar and
satellite indicate a decreasing trend in showers and clouds.
Several stations N/w of PHL have reported some light rain, just
a couple hundredths of and inch at most. As expected winds have
picked up from the west and are gusting up to around 25 kt.

For tonight, precip will be gone and clouds will mostly clear
out with a drier air mass and strong subsidence moving in. One
minor exception is over the higher Poconos where some sprinkles
or flurries are possible this evening. A deepening surface low
to our NE and high pressure building in from the west will
maintain a rather tight pressure gradient across the area. This
along with low cold advection should keep gusty NW winds going
through much of the night. Overnight min temps look to be about
10 deg F colder than this morning.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
For Friday, the upper level trof moves offshore to be replace
by ridging aloft. The ridge of surface high pressure will
approach from the west but with weakening trend. The airmass
remains rather dry with possibly just a few high clouds spilling
over the upper ridge. Winds will continue NW and somewhat gusty
in the morning, with some downward mixing of momentum, but less
so in the afternoon. Temps will be a few degrees cooler than
today, but with plenty of sunshine.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
The main focus in the extended will be the storm system
expected Saturday through Sunday. Otherwise, fairly quiet
weather through much of the rest of the extended period.

Friday night is expected to be rather tranquil as high pressure
weakens across the area, then retreats southward. No
precipitation is expected through Friday night.

However, as we move into Saturday, strong south to southwest
flow begins to develop during the day between the departing high
pressure to our south, and an area of low pressure moving
through the Ohio Valley and into the eastern Great Lakes.
Meanwhile, a warm front is forecast to lift across the area
during the day Saturday as well as a short wave/vorticity
impulse slides north across the area as well. This is expected
to lead to a period of showers during the afternoon, especially
along and north of the I-95 corridor. South to southwest winds
are expected to increase through the day as well, with gusts
reaching 25-35 mph.

As we move into Saturday night, a strong cold front is expected
to move across the area. Ahead of this front, gusty southwest
winds will continue through the night with gusts of 25-35 mph
possible. As the front moves through during the overnight,
shower chances will be increasing across the area, and move from
west to east fairly quickly. There is not much instability
forecast, so we do not have thunder in the forecast at this
time. However, PW values increase to 1.00-1.25 inches, so there
could be some moderate, to occasionally heavy rainfall at times.

The cold front is expected to have moved through the area, and
either be offshore, or just along the coastal areas of New
Jersey and Delaware by around daybreak Sunday. Showers will come
to an end behind the cold front, with the exception of possible
continued showers in the Poconos as some lake effect streamers
may develop. As the strong cold front moves across the area,
winds will continue to be gusty, but become west to northwest as
it shifts eastward. Wind gusts could reach 35-40 mph at times
as the front crosses the area early Sunday, before slowly
diminishing during the day.

As we go into Sunday night, winds could remain gusty around
20-30 mph and all precipitation is expected to have ceased. The
only exception is the possibility for some flurries in the
Poconos Sunday evening.

High pressure builds to our south Monday into Tuesday. Dry
weather is expected Monday through Tuesday, but winds will
likely remain gusty around 20-25 mph.

A cold front is forecast to move across the area Tuesday night
into early Wednesday morning, but it is currently expected to be
a dry frontal passage. High pressure is expected to then build
across the area later Wednesday into Thursday.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR conditions expected. Some cigs bkn050-060
possible around RDG and ABE this evening, clearing overnight.
Winds should continue to gust NW around 25 kt this evening but
may die down for a while overnight. Confidence in VFR is high;
in wind gusts overnight is average at best.

Friday...VFR conditions. Some NW wind gusts to around 20 kt
through midday, decreasing in the afternoon. Confidence is high.

OUTLOOK...

Friday night...VFR conditions expected. High confidence.

Saturday...VFR early, with deteriorating conditions through the
day with scattered showers during the afternoon associated with
a warm front. Gusty south-southwest winds 20-25 knots. Moderate
confidence.

Saturday night...IFR conditions likely, with periods of showers
associated with a cold front. Gusty southwest winds 30-35 knots
possible. Moderate confidence.

Sunday...Improving to MVFR, then VFR behind the cold frontal
passage. Gusty west-northwest winds 30-35 knots. Moderate
confidence.

Sunday night...Generally VFR. Gusty northwest winds 25-30
knots. Moderate confidence.

Monday...Generally VFR. Gusty west-northwest winds 20-25 knots.
Moderate confidence.

Monday night-Tuesday...VFR. Winds may gust 15-20 knots during
the afternoon Tuesday. Moderate confidence.

&&

.MARINE...
The Gale warning remains in place, starting at 21z and
continuing to 11z Friday morning. NW winds will be increasing
late this afternoon and evening with frequent gale force gusts
expected during the night. Seas will build to 4-6 feet well
offshore and 3-5 ft over the lower Delaware Bay. Winds and seas
will gradually subside on Friday, but a SCA will likely be
needed during much of the day. Otherwise clear skies are
expected.

OUTLOOK...

Friday night...Conditions fall below advisory levels.

Saturday-Sunday night...An extended period of gale force wind
gusts are expected starting Saturday afternoon, then continuing
Saturday night through early Sunday night. Conditions likely to
lower to Small Craft Advisory levels overnight.

Monday-Tuesday...Small Craft Advisory conditions expected to
continue into Monday and Tuesday. A brief lull may be possible
late Monday into Monday evening.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Warning until 6 AM EST Friday for ANZ430-431-450>455.

&&

$$

Synopsis...Robertson
Near Term...AMC
Short Term...AMC
Long Term...Robertson
Aviation...AMC/Robertson
Marine...AMC/Robertson


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