266
FXUS61 KPHI 012103
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
503 PM EDT Mon Sep 1 2025

.SYNOPSIS...
High pressure centered to our north through tonight will gradually
weaken as is shifts to our east Tuesday and Wednesday. A cold front
cross our area during Friday, followed by another cold front later
Saturday. High pressure then builds in during Sunday and Monday.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
Fair conditions will continue tonight through Tuesday night as high
pressure remains near the Canadian Maritimes, while it noses its way
into the Mid Atlantic region. This will keep a northeast to east
wind direction, allowing for temperatures to remain near normal
through Tuesday night. There will be scattered to broken clouds,
especially as daytime fair weather cumulus clouds develop, but no
widespread precipitation is expected at this time. For this
afternoon, there may be some reflectivities on the radar, but this
should mostly be the actual clouds, or precipitation that melts
before reaching the ground. If a sprinkle did reach the ground, it
would not amount to much. There is a better chance, albeit slight,
for a few showers to develop across the far southern areas toward
daybreak Tuesday into the daytime Tuesday, but most places will
remain dry.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A weak shortwave trough lifts out of New England Wednesday as a
closed low tracks near the upper Great Lakes. The closed low is
forecast to shift eastward across mostly Canada with it tending to
just glance our region during Thursday. This feature will drive
surface low pressure well to our north, however its cold front will
start to enter our area late Thursday night. A southerly flow is
forecast to increase some ahead of this front, and this will result
in some more moisture advecting northward across our area. A little
more humid feel to the air should occur Thursday and Thursday night
ahead of the cold front. Prior to this however, surface high
pressure weakens and shifts to our east Wednesday. An initial
increase in the low to mid level moisture Wednesday night could
result in areas of low clouds and/or fog, which lingers into
Thursday morning.

The guidance continues to slow the arrival of the cold front later
Thursday and we have noticed the delay/decrease in the National
Blend of Models (NBM) PoPs Thursday and Thursday night. This slower
trend looks more correct given that the initial strong shortwave
energy rolls northeastward well to our northwest with the main
trough hanging back well to our west. The NBM used in this forecast
is probably still on the quicker side with the PoP arrival/increase
eastward Thursday afternoon. The high temperatures Wednesday look to
be mostly below average, then rising to or slightly above average on
Thursday.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Summary...More humid to start with a chance for some
showers/thunder, then cooler and much drier into early next next.

Synoptic Overview...A strong upper-level trough (closed low)
centered from south-central Canada to near the Midwest is forecast
to gradually shift eastward some and weaken. However, a form of this
trough is forecast to arrive in the Northeast and Mid-Atlantic into
early next week. This will drive a cold front across our area Friday
with a secondary cold front arriving on Saturday. High pressure then
builds in during Sunday and Monday.

For Friday and Saturday...A more humid air mass is forecast to be in
place ahead of a cold front Friday. An initial closed low centered
across south-central Canada is forecast to pivot eastward and
gradually weaken with time. This will support surface low pressure
well to our northwest. A trailing cold front is anticipated to cross
our area during Friday and a plume of deeper moisture will be in
place ahead of it. The forecast challenge is how much forcing for
ascent on the larger scale but also by the cold front is present.
Given that the parent trough hangs back well to west and also is
forecast to weaken some, an area of showers and embedded thunder may
weaken as they cross our area through Friday morning. It will depend
on the strength/focus of the forcing. The cold front may be slow to
work its way completely through our area during Friday, therefore
delaying the arrival of lower dew points. This would also keep the
chance for some convection Friday afternoon and evening before the
front shifts offshore. Some convection could be on the stronger side
Friday and/or Saturday afternoons, however this will depend on the
magnitude of the forcing and instability/shear. Most if not all of
the area could use some rain, however this cold front does not
appear to deliver widespread showers with heavy amounts of rain.

A secondary cold front arrives later Saturday tied more with the
incoming upper-level trough. The parent low once again is well north
of our area, therefore it will come down to how much forcing will be
presence for shower/thunder development. A pre-frontal trough may
also be across the area that could focus some convective development
well ahead of the actual cold front. The warmth looks to peak on
Saturday with many areas getting into the 80s, then following the
cold front a much drier air arrives at night with also cooling.

For Sunday and Monday...The aforementioned upper-level trough may
become more fragmented as a couple of strong shortwaves peel off to
the northeast. The trough axis may end up remaining to our north and
west with some ridging into the western Great Lakes into adjacent
Canada. This ridge supports surface high pressure expanding eastward
and building into our area during this time frame. This brings in a
Canadian air mass which is much cooler and rather dry (dew points
may drop into the 40s). Given high pressure building in and also the
much drier air, both days are forecast to be rain-free.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

This afternoon...VFR conditions prevail. Northeast to east winds
5-10 knots, with gusts around 15-20 knots. High confidence.

Tonight...VFR conditions continue. Winds likely shift to east to
southeast this evening, then light and variable most places
overnight. Any direction will shift back to the northeast. High
confidence.

Tuesday...Mostly VFR conditions expected. There is a chance for a
brief period of MVFR ceilings around daybreak, especially for ACY
and MIV. Northeast to east winds 5-10 knots increase to 10-15 knots
with gusts 15-20 knots through the day. High confidence.

Tuesday night...VFR conditions continue. Winds likely shift to east
to southeast during the evening, then light and variable most places
overnight. Any direction will shift back to the northeast. High
confidence.

Outlook...

Wednesday...MVFR ceilings and/or visibilities possible late at
night.

Thursday and Friday...MVFR ceilings and/or visibilities early
Thursday morning. Sub-VFR conditions possible with some showers,
mainly Thursday night and Friday.

Saturday...A few showers/thunder possible, otherwise VFR.

&&

.MARINE...
This afternoon through Tuesday night...Conditions are expected
to remain below advisory levels. However, winds will gust in the
low 20s on through this afternoon, and seas will be 4+ feet.

Outlook...

Wednesday...The conditions are anticipated to be below Small Craft
Advisory criteria.

Thursday and Friday...Southerly winds increase ahead of a cold front
and wind gusts could approach 25 knots for a time.

Saturday...The conditions are anticipated to be below Small Craft
Advisory criteria.

Rip Currents...

Tuesday...Northeasterly wind 10 mph will become east-
northeasterly in the afternoon. Breaking wave heights 2 to 3
feet, with a 7-9 second period. Given the forecast trend of wind
being more onshore, have opted for a MODERATE risk for the
development of dangerous rip currents at all beaches.

Wednesday...Northeasterly wind 10 mph will become east-
southeasterly in the afternoon. Breaking wave heights 2 to 3
feet, with a 7-9 second period. Given the forecast trend of wind
being more onshore, have opted for a MODERATE risk for the
development of dangerous rip currents at all beaches.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Gorse
NEAR TERM...Robertson
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Gorse/Robertson
MARINE...AKL/Cooper/Gorse/Robertson