884
FXUS61 KPHI 040535
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1235 AM EST Thu Dec 4 2025

.SYNOPSIS...
High pressure, centered to our south, moves offshore overnight.
An arctic front will move across our region Thursday. The center
of arctic high pressure builds into our area later Thursday night
and Friday morning before shifting offshore by later Friday. An
area of low pressure tracks to our south and east later Friday
into Saturday, followed by a cold front later Sunday. High pressure
builds in later Monday into Tuesday, then low pressure and a cold
front may arrive later Tuesday into Wednesday.

&&

.NEAR TERM /THROUGH TODAY/...
An expansive area of high pressure is over the Eastern US, which
will result in a continuation of tranquil conditions overnight.
Skies will remain mostly clear outside of some thin passing
high clouds and perhaps some stratus over the higher elevations
in the Poconos. Temperatures have already dropped into the 20s
in most areas and will fall a few more degrees overnight. Across
Philly metro temps will remain closer to 30 with the urban heat
island effect.

For Thursday, a cold front will pass through the region, ushering
in an arctic airmass. While the frontal passage will mainly be
dry for most, there may be just enough moisture, lift, and instability
to result in a few snow showers along and north of I-80 during the
day. While this should generally be not impactful, the snow squall
parameter is not zero, so a few squalls reaching the far northern
part of our area cannot be ruled out. Otherwise for most, the main
impact will be increasing winds as the front passes and in its wake
as strong cold-air advection ramps up. Winds increase with gusts
around 25-35 MPH expected out of the northwest. Temperatures will
be in the mid to upper 30s and low 40s Thursday, but it will certainly
feel cooler than that with a brisk northwesterly wind.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
Arctic air settles in for the end the week and to start the weekend.

Following the passage of an arctic front, the center of arctic high
pressure will gradually build into our region Thursday night. As
this occurs, a gusty northwesterly wind will diminish through
Thursday evening. Due to the strong cold air advection, temperatures
will drop significantly Thursday night and bottom out in the teens
(some single digits in the Poconos to far northwestern New Jersey)
by daybreak Friday. There will be a wind chill factor as well,
however this will be mostly during the evening as the winds are
expected to mostly decouple during the night. Some record low
temperatures could be challenged for December 5th, especially in the
Lehigh Valley and Berks County. Record low temperatures are listed
below in the climate section for reference.

The center of arctic high pressure across our area to start Friday
morning shifts offshore by later in the day. A shortwave trough
however arrives later in the day Friday and especially Friday night.
This feature does not appear to sharpen a lot as it arrives given
the more zonal flow aloft ahead of it. The deterministic and
ensemble guidance varies with the northward placement of the
precipitation shield. A cold/dry air mass is forecast to be in
place, and this may hinder the northward extent of the precipitation
shield. Surface low pressure is forecast to develop and track to our
south as a result of the incoming mid level energy and it looks to
be a quick mover. Given the current synoptic setup, the highest
probability of precipitation remains across Delmarva to southeastern
New Jersey. There is the potential for light snow accumulations
especially the farther south one goes across the area, with some
potential for a wintry mix or a change to rain closer to some of the
coastal areas. Some guidance is a bit stronger and northward with
the precipitation shield, which offers more snow. If a ribbon of
stronger forcing develops (frontogenesis or strengthening
frontogenesis), then a more expansive precipitation shield would be
plausible and perhaps a banding feature north/northwest of the
surface low. This would tend to occur if the mid level wave sharpens
some more. The details will be determined by the track and strength
of the system which will then determine the precipitation types and
snow amounts. As of now though, snow amounts are an inch or less.
Rather cold Friday with highs ranging from the mid to upper 20s far
north to upper 30s far south, however the wind looks to be on the
light side and therefore not much of a factor.

The system quickly departs Saturday with some decrease in the cloud
cover. It should not be quite as cold Saturday, however still
remaining below average.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Synoptic Overview...An upper-level trough is forecast to be
across much of eastern Canada Sunday and Monday. This feature
looks to extend south across much of the eastern U.S. especially
as stronger shortwave energy travels along the southern parts
of the trough into the Southeast U.S. The trough may weaken
Tuesday into Wednesday, however this will depend on if a strong
shortwave dives southeastward from the Midwest Monday night and
Tuesday. At the surface, a cold front arrives later Sunday with
high pressure sliding across our area Monday into Tuesday. Low
pressure and its cold front may then arrive later Tuesday into
Wednesday.

For Sunday and Monday...An upper-level trough across much of eastern
Canada amplifies southward as shortwave energy rounds its base
across the southern states. As this occurs, a cold front looks to
cross our area later Sunday. The moisture with this looks to be
rather limited and therefore much of the area should remain dry.
However, this front will deliver another shot of cold air into our
area for Monday. Temperatures are forecast to remain below average,
with it being much colder/below average on Monday. As the axis of
high pressure moves across our area Monday night, temperatures are
forecast to be very cold with lows in the teens (single digits
across the far north).

For Tuesday and Wednesday...Despite that the main upper-level trough
may weaken or retreat more to our north Tuesday, a potentially
strong shortwave trough diving southeastward from the Midwest should
cross our area Tuesday night into Wednesday. This feature may end up
supporting a clipper-type system at the surface, which then quickly
crosses our area Tuesday night into Wednesday. The moisture is
typically limited with these features, however if the mid level wave
is stronger like some guidance suggests then forcing for ascent
would be stronger. There is uncertainty with this given all the
moving pieces within the parent upper-level trough, therefore did
not deviate from the National Blend of Models (NBM) guidance.
Cold/below average temperatures continue, however as of now a little
moderating of the temperatures are forecast for Wednesday.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of tonight (through 12Z)...VFR. West/southwest winds 5 kt
or less.

Thursday...VFR. Winds increasing with a frontal passage between 14z-
16z. West/northwest winds 10-20 kt with gusts around 25 kt.
High confidence in prevailing VFR, moderate confidence in timing of
frontal passage and winds increasing.

Outlook...

Thursday night...VFR. West-northwest winds diminishing.

Friday and Saturday...A period of sub-VFR conditions possible along
with some rain/snow (highest probability currently south and east of
KPHL) later Friday into early Saturday.

Sunday and Monday...Mostly VFR.

&&

.MARINE...
No marine headlines expected through tonight. West winds around 10-
15 kt with seas 2 to 4 feet.

A Small Craft Advisory goes into effect for all marine zones beginning
at 14z. West/northwest winds around 15-25 kt with gusts around 30
kt expected. Seas 3 to 5 feet.

Outlook...

Thursday night...Small Craft Advisory conditions in the evening,
with winds and seas decreasing through the overnight.

Friday through Monday...The conditions are anticipated to be below
Small Craft Advisory criteria.

&&

.CLIMATE...
Very cold temperatures are forecast for early Friday morning which
may challenge a few record lows.

Record Low Temperatures for December 5th...

SITERECORD/YEAR
Allentown (ABE)11/1926
AC Airport (ACY)11/1966
AC Marina (55N)15/1901
Philadelphia (PHL) 13/1886
Wilmington (ILG) 12/1926
Reading (RDG) 12/1926
Trenton (TTN) 10/1926
Mount Pocono (MPO) -2/1971
Georgetown (GED) 14/1966

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 9 AM this morning to 10 PM EST this
     evening for ANZ430-431.
     Small Craft Advisory from 9 AM this morning to midnight EST
     tonight for ANZ450>455.

&&

$$

SYNOPSIS...Gorse
NEAR TERM...Hoeflich
SHORT TERM...Gorse/MJL
LONG TERM...Gorse
AVIATION...Gorse/Hoeflich/MJL
MARINE...Gorse/Hoeflich
CLIMATE...