670
FXUS61 KPHI 061852
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
152 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 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 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 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 Tuesday...Prevailing VFR.

Wednesday...Sub-VFR conditions will be possible with a chance
(20- 40%) of 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...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...Cooper
SHORT TERM...Cooper/Johnson
LONG TERM...Cooper/Johnson
AVIATION...Cooper/Johnson
MARINE...Cooper/Johnson
TIDES/COASTAL FLOODING...
CLIMATE...