618
FXUS61 KPHI 072301
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
601 PM EST Sun Dec 7 2025

.SYNOPSIS...
A cold front will cross the region and move offshore overnight,
ushering in arctic high pressure with much colder and drier
conditions through Tuesday. A quick moving low pressure system
and its associated fronts will impact the region on Wednesday,
then a clipper system will impact the area Thursday night into
Friday. Arctic high pressure will then return into next weekend,
resulting in a prolonged period of well below normal
temperatures.

&&

.NEAR TERM /THROUGH MONDAY/...
A mid-level shortwave axis associated with a closed low over
portions of the Hudson Bay and Quebec will shift southeast to
the north of the region into tonight. At the surface, a strong
cold front will pass through the region tonight into early
Monday morning.

It still appears that the front itself will be mostly dry for
our area, with limited moisture and the primary synoptic scale
ascent displaced to the north. With that said, it is not
entirely out of the question that a few flurries could occur
tonight, primarily across the Poconos. The main impacts will be
the dramatic temperature difference and wind changes. Guidance
tends to have a low bias with arctic cold air advection regimes
even if the trough isn`t very amplified (as this one doesn`t
appear to be), so have included wind speeds and gusts on the
higher end of guidance. Even so, should stay well below wind
advisory thresholds. The peak gusts in our region will likely be
in the 25 to 35 mph range, with gusts as high as 40 mph
possible for the Poconos.

Low temperatures tonight look to be in the upper 10s to lower
20s across most of eastern PA and northern NJ, and in the mid to
upper 20s elsewhere.

Flow aloft will weaken into Monday as another impulse
approaches the Eastern Seaboard to the south of the area by
evening. At the surface, strong high pressure will build in from
the Great Lakes region. A weak area of low pressure associated
with the impulse to the south of the area is expected to develop
near the coast Monday, but the strong high should keep it and
most of the associated precipitation to the south. The far
northern part of the precipitation shield could potentially make
it as far north as portions of the eastern shore of Maryland
and far southern Delaware, where it would fall as snow. PoPs are
in the 20-30% range for this area during the late morning and
into the afternoon hours. Little to no accumulation would be
expected with any snow given its very light nature.

High temperatures on Monday will be quite chilly. Low-mid 20s
are expected across the Poconos and into far northwestern NJ.
Near- freezing temperatures can be expected across the remainder
of eastern PA and NJ away from the coastal plain, where they
could perhaps reach the mid 30s.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
The main story for the short term period Monday night through
Tuesday will be the continued well below normal temperatures (on
the order of 10-20 degrees below normal) following a cold
frontal passage late tonight (Sunday night).

A split flow pattern will remain in place through early in the
new week, with the main feature of interest being a trough axis
passing to our south Monday night. Rather cold and dry arctic
high pressure will build in from the Great Lakes through Tuesday
morning. The high will then shift offshore during the day
Tuesday, with some south to southwesterly return flow developing
later in the day.

The coldest night of the week and likely so far this season for
most areas will be Monday night into Tuesday morning. As the
high pressure builds in over the area maximizing subsidence,
skies should clear out enough to give us decent radiational
cooling conditions. However, there will be considerable mid
level cloudiness dissipating early in the night. The lingering
mid level moisture will probably inhibit any extreme bottoming
out of temperatures despite dewpoints near 0 degrees, especially
with a lack of snowpack. Forecast low temperatures range from
the single digits for the Lehigh Valley, NW NJ, and southern
Poconos, to the low to mid 10s in most other areas, and closer
to 20-25 degrees for the immediate coastal areas. Fortunately,
winds will be light to calm, so the wind chill will not be much
of a factor and no cold weather headlines are anticipated.

These temperatures are anomalously cold, but are currently
anticipated to fall just shy of record values. For more details
on daily records, see the Climate section below

As the high pressure shifts offshore on Tuesday, we will start
to develop some return flow and airmass modification into the
afternoon hours. High temperatures will rebound a few degrees,
mainly in the low to mid 30s and closer to 40 degrees near the
coast. Increasing clouds through the day. With the high pressure
offshore for Tuesday night, we will keep a light south to
southwest breeze near 5-10 mph much of the night. This combined
with broken cloud cover will significantly limit radiational
cooling, so low temperatures should range mostly from the mid
20s to low 30s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The pattern from the middle of the week into next weekend
remains cold with below normal temperatures, but becomes more
active across the Eastern US with several areas of low pressure
and their associated fronts taking aim at the area.

Guidance has come into better agreement with Wednesday`s system
as a rather strong shortwave tracks through the Great Lakes
with an upper level low meandering within the vicinity of the
Hudson Bay. At the surface, low pressure will track out of the
Great Lakes and across southern Quebec into Wednesday night. As
it does so, its associated cold front will cross through the
Mid-Atlantic region. This will be the next opportunity for much
of the area to recieve some kind of precipitation ahead of FROPA
on Wednesday. With the region located well south of the low
center, its likely that this precipitation will be mostly in the
form of rain, although some snow is likely in the southern
Poconos.

Temperatures for Wednesday will be close to normal, with highs
in the 40s to near 50 degrees in most areas and nighttime lows
in the upper 20s to mid 30s. Following the frontal passage,
temperatures are expected to dip back a bit below normal for
Thursday as some weak ridging at the surface returns. Aloft, the
Mid-Atlantic will remain nestled well under the deep trough,
yielding the continuation of cool weather.

Beyond Thursday and continuing into next weekend, guidance
diverges significantly with the timing, position and strength of
features. As of now, it does appear that will be some sort of
`clipper-like` system that will move into the region Thursday
night into Friday. This system looks to be a rather quick mover,
but temperatures will be cool thanks to the frontal passage the
day prior. This could result in a period for light snow and/or
light rain across the area, but ultimately comes down to timing
and the track of the low. For this reason, kept NBM guidance
which depicts a 30-40% chance of light rain/snow across much of
the area.

Heading into next weekend, an arctic outbreak with well below
normal temperatures looks to be on the horizon beginning next
weekend. A few consecutive days of temperatures on the order of
10-20 degrees below normal are looking increasingly likely. The
exact magnitude of the cold still is a little uncertain at the
moment, but looking like roughly 4 days or so of highs near to
below freezing and lows in the 10s to low 20s across the board
beginning Saturday and into early the following week. Persistent
west to northwest winds near 10-15 mph will result in wind
chills as low as the single digits at night. Some snow is
possible sometime Saturday as well, but this will depend on the
amplitude and timing of the trough axis, and if any surface low
pressure can consolidate.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR. Some SCT to BKN clouds around 4 kft this evening
then just FEW/SCT high clouds. LGT/VRB wind to start will
become north- northwest 10-15 kt with gusts near 20 kt with cold
frontal passage between 06-08Z. High confidence overall,
moderate confidence in timing of the front and associated
windshift.

Monday...VFR. BKN high clouds. North-northeast wind 10-15 kt
with gusts to 20-25 kt, decreasing to near 10 kt by late
afternoon. High confidence.

Outlook...

Monday night through Tuesday night...VFR. no significant
weather. LLWS possible Tuesday night.

Wednesday through Friday...Restrictions possible (30-50%
chance) in low clouds and rain/snow. LLWS possible on Wednesday.

&&

.MARINE...
Small Craft Advisory will be in effect beginning at 1 AM Monday
for all ocean zones as well as the Delaware Bay.

Winds generally westerly and increasing to 10-15 kt this
evening, becoming northerly around 20-25 kt with gusts around 30
kt overnight and into the day Monday. Winds are expected to be
slightly lower over the Delaware Bay, but still expect frequent
gusts to around 25 kt. Seas increase from 2-3 feet this evening
to 4-6 feet overnight and remain elevated through Monday.

Outlook...

Monday night...Advisory conditions expected to continue into
the night for much of the Atlantic coastal waters. North to
northeast winds diminishing to around 10-20 kts, but seas will
remain near 4-6 feet.

Tuesday...No marine hazards expected.

Wednesday through Thursday...Advisory conditions likely. Winds
increasing to near 20-30 kts and seas building 5-8 feet. A
chance of rain.

Friday...No marine hazards expected. A chance of rain and snow.

&&

.CLIMATE...
Very cold Monday Night into Tuesday Morning. At this point, we
aren`t forecasting to break any record lows. Below are the
record lows for December 9.

SITERECORD/YEAR
Allentown (ABE)      7/2002
AC Airport (ACY)     6/1968
AC Marina (55N)      5/1876
Philadelphia (PHL)   6/1876
Wilmington (ILG)    13/1960
Reading (RDG)        0/1989
Trenton (TTN)       12/2002
Mount Pocono (MPO)  -1/1902
Georgetown (GED)    10/1976

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 1 AM to 6 PM EST Monday for ANZ430-
     431-450.
     Small Craft Advisory from 1 AM Monday to 1 AM EST Tuesday for
     ANZ451.
     Small Craft Advisory from 1 AM Monday to 5 AM EST Tuesday for
     ANZ452>455.

&&

$$

SYNOPSIS...Staarmann
NEAR TERM...Cooper/Fitzsimmons/Johnson
SHORT TERM...Staarmann
LONG TERM...DeSilva/Staarmann
AVIATION...Cooper/Fitzsimmons/Staarmann
MARINE...Cooper/Staarmann
CLIMATE...