178
FXUS61 KPHI 061737
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1237 PM EST Sat Dec 6 2025

.SYNOPSIS...
Through the day today, our region will be sandwiched between the
departing low pressure system moving further off shore and the
next approaching cold front in the Great Lakes Region. By Sunday
night, that cold front will cross through our region. In the
wake of that front, high pressure builds in for the first half
of the work week. The second half of the week could be active,
with potentially two low pressure systems getting close to the
region in that period.

&&

.NEAR TERM /THROUGH TONIGHT/...
A very complex forecast continues this morning as periods of light
freezing drizzle, drizzle, light snow, and sleet have been observed
along the I-95 corridor. The surface low that brought some light
snow to the area yesterday, continues to pull away, however, a
residual weak surface trough lies just off the coast of New Jersey.
This trough is enhancing lift across portions of the area this
morning. As it does so, low-level moisture remains trapped under an
inversion around 960 mb which is shown in the PHL ACARS sounding.
Temperatures at the inversion level have been mostly below 0C,
however gradual warming above 0C is occuring, where light snow is
now transitioning to pockets of drizzle and/or freezing drizzle.
Perhaps a light glaze of ice accretion is possible where freezing
drizzle occurs, but the overall aspect is that this will be rather
isolated in nature. Also, a light dusting of snow is possible up in
the higher terrain of north Jersey. As a result, a Special Weather
Statement is in effect through 8 AM for portions of the area which
may continue to observe isolated areas of hazardous travel for the
next several hours. Light frozen precipitation should come to an end
thereafter once surface temperatures warm above freezing.

Improving weather conditions are then expected as the day progresses
with the main trough axis approaching from the west. At the surface,
the area will be caught in between systems, resulting in a weak,
brief period of ridging. As a result, mostly cloudy to overcast
skies this morning, will begin to lift and scatter out this
afternoon. Temperatures will moderate some with winds having a more
westerly component to them, where highs are to range from the mid
30s to mid 40s. Tonight, skies will be mostly clear early, but some
high level clouds will filter in after midnight as another weak
impulse approaches. With winds generally less than 5 mph under
mostly clear skies, radiational cooling appears optimal. Lows look
to range from the upper teens to upper 20s for most. For areas which
still have snow on the ground from recent snowfall, temperatures may
end up being much lower than what is currently forecast.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
A cold front is expected to cross our region Sunday
evening/overnight, ushering in much colder air.

The biggest change from previous model runs is that the
associated trough isn`t as amplified. What this means for
ultimate impacts is the chance for precipitation has decreased
and the blend of guidance for wind speeds/gusts has decreased
slightly.

Stayed close to the blend of guidance for the chance for
precipitation, which now means that we don`t have any mention of
precip in our area. However, will be keeping a close eye on
guidance trends especially for the Poconos.

For winds however, I included wind/wind gust speeds on the
higher end of the blend of guidance for the 12 hours following
the frontal passage. This is more in line with model soundings
showing a potential for wind gusts above 30 mph.

In the wake of the cold front, temperatures, especially Monday
and Monday Night, will be well below normal, as much as 20
degrees below normal. For now, have stayed pretty close to the
blend of models. However, there are some factors suggesting that
guidance could have a warm bias on Monday night/Tuesday
morning. During that time, the surface high will likely be
situated over our region, with clear skies and very light winds.
These types of efficient radiational cooling patterns tend to
end up colder than the median blend of guidance. Previous model
runs were depicting the potential for clouds to build in Tuesday
morning, but with the latest guidance, the chance has
decreased. None the less, with the latest guidance, even if we
verify at the 10th percentile of guidance for min temperatures,
we should still stay above cold weather advisory criteria.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The long term period is still rather muddled in terms of confidence
in model runs owing to a split flow pattern and minor differences in
the timing and evolution of the two low pressure systems that are
possible at the end of the week.

Beginning Tuesday night, we will be watching a shortwave
trough dig southeastward across the Northern Plains and into the
Great Lakes region. It should pivot through or just northwest of
the region on Wednesday. In a sharp contrast from previous model
runs, some guidance is depicting this a weak and fast moving clipper
type system, while other guidance continues to show it interacting
with a closed low over Canada, resulting in a broad trough setting
up over the eastern seaboard. Depending on how quickly that system
moves out, a second short wave trough could dig through the
Dakotas/Minnesota area into the Mid Atlantic by Friday.

Using a blend of guidance shows a broad chances for precipitation
from Wednesday through Friday. However, I don`t expect the second
half of the week to be a washout; this is more an artifact of timing
differences between guidance. It is more likely that if we see any
precipitation, it will come in two distinct periods with the two
different systems.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Through 00Z...MVFR and even brief periods of IFR ceilings
remain for KILG, KMIV, and KACY. Some drizzle continues to cause
MVFR visibility restrictions for KPHL as well. Any residual
drizzle should dissipate, with ceilings lifting/scattering out
by 19-21Z. VFR for all terminals thereafter. West wind 5-10 kt.
Moderate confidence overall. Low confidence in exact timing of
improvement to VFR given the persistence of low ceilings and
drizzle.

Tonight...VFR with mostly clear skies. West wind 5 kt or less
becoming light and variable with calm periods. High confidence.

Sunday...VFR. Southwesterly wind 5-10 kt. High confidence.

Outlook...

Sunday night through Tuesday...Prevailing VFR.

Wednesday...Sub-VFR conditions will be possible with a chance
(20- 40%) of rain.

&&

.MARINE...
No marine headlines are in effect through tonight. North-northeast
winds around 5-10 kt this morning, will settle out of the northwest
this afternoon into tonight around 10-15 kt. Occasional gusts up to
20 kt possible tonight. Seas of 2-4 feet. A chance for drizzle this
morning, otherwise fair weather.

Outlook...

Sunday...Winds and seas will stay below SCA criteria.

Sunday Night through Monday...SCA conditions are expected and gale
conditions are possible behind a cold front Sunday Night that will
also bring an abrupt shift to northwesterly winds. There is a 20 to
40% chance that gale force conditions will develop in this period.

Tuesday...wind and seas should stay below SCA criteria.

Tuesday Night through Wednesday...SCA conditions are likely with
wind gusts up to 30 KT and elevated seas up to 8 ft on the coastal
waters. While guidance suggests there is up to a 30% chance for gale
force gusts, especially Wednesday, the wind direction is unfavorable
for getting gales during the cold season, so have kept the forecast
below gale criteria for now.

&&

.TIDES/COASTAL FLOODING...
As a result of the Full Moon on December 4th, some minor tidal
flooding will be possible during the daytime high tides through
Sunday. This is primarily for the NJ and DE coasts and lower
Delaware Bay. It does appear that tidal departures will
increase slightly Saturday into Sunday, increasing the chance
for minor tidal flooding especially for the southern New Jersey
and Delaware coasts, including parts of the lower Delaware Bay.
However, latest guidance keeps water levels below advisory
thresholds.

No tidal flooding is expected elsewhere.

&&

.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...None.

&&

$$

SYNOPSIS...Cooper/Johnson
NEAR TERM...DeSilva
SHORT TERM...Cooper/Johnson
LONG TERM...Cooper/Johnson
AVIATION...Cooper/DeSilva/Johnson
MARINE...DeSilva/Johnson
TIDES/COASTAL FLOODING...
CLIMATE...