667
FXUS61 KPHI 061937
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
237 PM EST Sat Dec 6 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 SUNDAY/...
A subtle mid-level impulse traversing the region will move
offshore by this evening. The region will remain under enhanced
westerly flow aloft through Sunday with a shortwave axis
associated with an upper- low over the Hudson Bay to the
northwest of the region and a large scale trough over the
eastern half of the Continental US. At the surface, broad high
pressure will build in from the west, with a strong cold front
beginning to approach western portions of the area by the
evening hours.

Low clouds and patchy drizzle have been persistent into this
afternoon, but the drizzle is finally departing. Clouds should
follow, with clearing from northwest to southeast this evening.
A good portion of the overnight hours are expected to be mostly
clear, before high level clouds begin to filter in again towards
sunrise. Winds will be light tonight, favoring a westerly or
northwesterly direction. Lows look to be in the low to mid 20s
outside of the coastal plain and urban corridor, where they
should bottom out in the upper 20s to near 30. Worth noting is
that while not currently anticipated, some patchy fog is not
entirely out of the question, especially in areas that saw
prolonged light precipitation into this afternoon. If this were
to occur, freezing on elevated surfaces would be a concern.

Widespread high clouds are likely to continue overspreading the
region on Sunday. Winds will become southwesterly but remain
relatively light around 5-10 mph. High temperatures look to be
in the mid to upper 30s northwest of the fall line, and the low
to mid 40s southeast.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
The main story for the short term period Sunday night through
Tuesday 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 next
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 trend in a less amplified trough continues, and thus
appears the frontal passage should be mostly dry, aside from
perhaps some flurries north of I-78. The surface high and
subsidence locally looks strong enough to keep the system
developing off the Carolina coast suppressed to our southeast.

With an overnight frontal passage Sunday night, low
temperatures into Monday morning won`t be exceptionally cold,
and should be mainly from the low to mid 20s (10s for the higher
elevations north of I-78). However, wind chills by dawn Monday
will be quite cold in the low to mid 10s across the board (as
low as 0 degrees across the Pocono Plateau) as northerly winds
increase to near 10-15 mph. High temperatures for Monday will be
the coldest of this arctic blast, ranging from the mid 20s to
mid 30s (low 30s for the I-95 corridor). With the continuing
northerly winds near 10-15 mph (gusting up to 25 mph), daytime
wind chills will only max out in the mid 10s to mid 20s.

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 /19Z 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 KMIV, and KACY, with VFR elsewhere. Ceilings should
lift/scatter out by 20-21Z. VFR for all terminals thereafter.
West wind 5-10 kt. Moderate confidence.

Tonight...VFR. West-northwest wind 5 kt or less. There is a low
chance (less than 20%) for the development of patchy fog.
Moderate confidence.

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

Outlook...

Sunday night through Monday...VFR. Gusty NNW winds developing
for Monday following FROPA.

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

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

&&

.MARINE...
No marine headlines are anticipated through Sunday. West-
northwest winds tonight will be 10-15 kt, and become west-
southwesterly on Sunday around 10 kt. Seas will be 2-4 feet.

Outlook...

Sunday night through Monday night...Advisory conditions
expected.northerly winds increasing to near 20-30 kts following
Sunday overnight FROPA. Some occasional gale force gusts near 35
kts possible. Seas building to 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.

&&

.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 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...Staarmann
NEAR TERM...Cooper
SHORT TERM...Staarmann
LONG TERM...Staarmann
AVIATION...Cooper/Staarmann
MARINE...Cooper/Staarmann
TIDES/COASTAL FLOODING...WFO PHI
CLIMATE...WFO PHI