140
FXUS61 KPHI 070637
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
137 AM EST Sun Dec 7 2025

.SYNOPSIS...
Weak high pressure will settle into the area tonight, then move
offshore and dissipate on Sunday. A cold front will cross the
region and move offshore Sunday night, ushering in arctic high
pressure with much colder and drier conditions through Tuesday.
Another low pressure and frontal system will impact the region
Wednesday, followed by yet another low pressure system late in
the week.

&&

.NEAR TERM /THROUGH MONDAY/...
Through Sunday morning, the key message is freezing fog,
primarily in Delmarva. Some freezing fog has developed
especially on portions of the MD eastern shore, so have issued a
freezing fog advisory for those areas as well as central and
southern Delaware. Looking at pavement sensors, most pavement
temperatures are hovering right above freezing, so the main
concern with any icing will be on bridges, but also can`t rule
out isolated slippery conditions on untreated roads.

Then, our attention turns to the cold front moving in tonight
into Monday morning. It still appears that the front itself will
be mostly dry for our area (though can`t rule out a few
flurries, especially for the southern 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 35 to 40 mph range.

Temperatures on Monday are expected to be 5 to 10 degrees lower
than Sunday, with highs only ranging from the lower 20s to mid
30s. Wind chill values are expected to be in the teens and 20s.

Also of note on Monday, one of the high res models - the HRRR -
depicted the low forming off the southeastern US coast on Monday
considerably further north that other models. If this were to
verify, it would mean that snow (albeit light in our area)
would be possible as far north as South Jersey. For now, this
appears to be an outlier, so have stayed close to the blend of
guidance.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
The main story for the short term period will be the well below
normal temperatures (on the order of 15-20 degrees below
normal) following a cold frontal passage Sunday night.

A split flow pattern will remain in place through early week,
with the main feature of interest being a trough axis passing to
our south Monday night. A dry cold front will push through the
region Sunday night as low pressure slides off to our northeast,
giving way to rather cold and dry arctic high pressure building
in from the Great Lakes through Tuesday morning. The high will
then shift offshore during the day Tuesday, with some SSW 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. Forecast low temperatures range from the
single digits near/north of I-78 to the low to mid 10s in most
other areas, and closer to 20 degrees for the immediate coastal
areas. Fortunately, winds will be light to calm, so the wind
chill will not be much of a factor.

As the high pressure shifts offshore on Tuesday, we will get
into 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.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Guidance diverges significantly on solutions to the forecast
for the middle to especially end of the week. Overall,
temperatures look to remain below normal through the end of the
week as a couple low pressure systems impact the region,
followed by potential for an arctic outbreak and sustained well
below normal temperatures next weekend.

It appears we`ll have a "warm up" of temperatures closer to
normal, but still a few degrees below normal for Wednesday ahead
of another frontal system. Forecast highs are in the low to mid
40s and near 50 degrees toward the coast. This system is more
likely to bring precipitation to portions of the region,
especially near/north of I- 78. Some snow is possible for the
higher elevations with rain more likely elsewhere. The
precipitation from this system will be insignificant, with
primarily some light rainfall and light (a dusting) of snow
anticipated at the moment.

Following frontal passage Wednesday night or early Thursday,
temperatures should fall a few degrees again. The next system
will probably impact the region Thursday night or Friday, so
we`ve maintained the chance PoPs for this time frame. Any
details with this late week system remain very unclear, as
guidance varies widely in the timing, track, and strength of it.
As with the Wednesday system, it currently appears to be a
relatively quick moving and insignificant system, but there`s
still time for that to change.

While technically outside the current forecast period, it
should be noted that 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 possible.

&&

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

Through 12Z...Prevailing VFR for most TAF sites with a ceiling
around 4000 ft AGL. However, for RDG, ILG, ACY, and especially
MIV, periods of BR or freezing fog will lead to visibility
reductions, mostly in the MVFR category. At MIV and locations
further south, a 200 ft ceiling has also developed leading to
prevailing LIFR conditions.

Sunday...VFR. Southwesterly wind around 5 kt. High confidence.

Tonight...VFR expected. Between 03 and 09Z, expect an abrupt
shift to northwesterly winds with wind speeds increasing to
10g20kt.

Outlook...

Monday...VFR. northwesterly wind gusts up to 30 kt possible.

Monday night through Tuesday night...VFR. No significant
weather.

Wednesday through Thursday...Restrictions possible (30-50%
chance) in low clouds and rain.

&&

.MARINE...
Winds and seas will stay below Small Craft Advisory conditions
today into this evening.

Late tonight into early Monday Morning, a cold front will cross
over the waters, bringing an abrupt shift from southwesterly to
northwesterly winds. Wind speeds will also increase quickly
behind this front. Wind gusts near or above 30 kt are forecast.
A Small Craft Advisory is in effect for the Atlantic Coastal
Waters and the Delaware Bay starting Late Tonight and continuing
through the day time on Monday. Winds are expected to slowly
begin to subside Monday Afternoon, but it may take time for the
seas to subside.

Outlook...

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.

&&

.TIDES/COASTAL FLOODING...
As a result of the Full Moon on December 4th, some spotty minor
tidal flooding will be possible during the daytime high tides
through this Sunday. This is primarily for the NJ and DE coasts and
lower Delaware Bay.

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...Freezing Fog Advisory until 9 AM EST this morning for
     DEZ002>004.
MD...Freezing Fog Advisory until 9 AM EST this morning for MDZ012-
     015-019-020.
MARINE...Small Craft Advisory from 1 AM to 6 PM EST Monday for ANZ430-
     431-450>455.

&&

$$

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