150
FXUS61 KPHI 091750
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1250 PM EST Tue Dec 9 2025

.SYNOPSIS...
The center of arctic high pressure gradually weakens and shifts
to our east today. Low pressure tracks to our north during
Wednesday with its cold front crossing our region Wednesday
evening. A cold front moves through Friday night or Saturday,
then low pressure along it tracks nearby Saturday into Sunday.
Arctic high pressure centered well to our west builds into our
region during early next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
High pressure over the area slides offshore later today. Arctic
airmass over the area results in high temperatures some 10 to
15 degrees below normal, generally in the 20s in the southern
Poconos to the low to mid 30s for most of the region, and in the
mid to upper 30s for southern Delmarva and along the Jersey
Shore. Skies clear out this morning, then high clouds build back
into the region as the afternoon progresses.

Return flow sets up behind the departing high, and after
temperatures drop in the evening, temperatures will mostly hold
steady through the overnight hours tonight generally in the mid
to upper 20s.

A clipper system over central Canada just north of the Northern
Plains will intensify as it dives into the Great Lakes tonight
through Wednesday morning. This system will move into western
and central New York on Wednesday before lifting into northern
New York by Wednesday evening.

Precipitation develops Wednesday morning initially over the
southern Poconos and the Lehigh Valley before spreading into New
Jersey and most of Delmarva. In terms of p-type, generally
expecting snow over the southern Poconos and far northwest New
Jersey, and snow precipitation will mostly be snow in the
southern Poconos and far northwest New Jersey throughout the
duration of the event. For the Lehigh Valley, precipitation will
start out as snow, followed by a brief period of wintry mix
which may include freezing rain for some spots, then rain by
Wednesday afternoon. For southern New Jersey, the I-95 corridor
including Philadelphia, and into northern Delmarva, a rain/snow
mix is possible initially before changing to plain rain late
Wednesday morning. Rain then continues through the day.

The highest snow accumulations are expected to be in the
southern Poconos, and especially the higher elevations, with as
much as 2 to 4 inches. Up to an inch is likely for northern New
Jersey and the Lehigh Valley, while trace amounts are possible
elsewhere. In the wintry mix/freezing rain areas, generally a
glaze of ice is possible.

Southerly flow ramps up ahead of the approaching low and with
the low passing north of the area, and this allows for strong
warm air advection. Highs warm back into the low to mid 30s for
the southern Poconos, and otherwise in the low 40s for northern
New Jersey and the Lehigh Valley. For southern New Jersey, the
Delaware Valley (including Philadelphia), and Delmarva, highs
will be in the mid to upper 40s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As as stronger upper-level through evolves across the East
during this time frame, strong low pressure will lift up across
northern New England to the Canadian Maritimes. A cold front
shifts to our east Wednesday evening and any precipitation is
expected to quickly come to an end. A notable breeze may occur
as cold air advection increases combined with enough vertical
mixing.

Plenty of cyclonic flow during Thursday and Thursday night
given the presence of the upper-level trough. A cold west-
northwest breeze will also be gusty and areas of stratocumulus
clouds may result. There will be a lake response and it is
possible that some flurries and snow showers get into portions
of our Pocono region and far northwestern New Jersey at times.
Temperatures continue below average, and with the wind factored
in the wind chill during the day will be mostly in the 20s
across the region. The winds should diminish at least some at
night, however wind chills look to get down into the teens for
most by daybreak Friday (single digits in the Poconos).

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Summary...Below average temperatures with another blast of
arctic air late in the weekend and/or early next week.

Synoptic Overview...A series of stronger shortwaves sliding
across southern Canada and the northern tier of the U.S. will
continue to result in an upper-level trough as it pivots across
central to eastern Canada. This will amplify an upper-level
trough more than once across the Northeast and Mid-Atlantic
regions. This will keep temperatures on the cold side. This
looks to favor mostly clipper systems (quick moving) with their
associated cold fronts crossing our region. A stronger trough
however over the weekend may result in a surface low developing
along a trailing cold front with this low tracking near our
area.

For Friday...As our region is on the southern side of a large
upper- level trough in central to eastern Canada, the axis of
weak high pressure slides across our area. A low pressure system
however tracks well to our north Friday night into Saturday
morning with a cold front crossing our area during Saturday.
This system looks to be moisture starved overall and therefore
may not produce much in the way of precipitation. Some
differences in the guidance on this therefore ran with the NBM
guidance which has 20-40 PoPs across the area.

For Saturday and Sunday...The cold front associated with the
aformentioned system may tend to stall to our south. The center
of arctic high pressure across the Midwest and northern Plains
will gradually build eastward. Ahead of this feature, a strong
shortwave may end up amplifying an upper-level trough across the
Northeast. This may result in a surface low developing along
the trailing cold front, which then tracks near our area. Some
guidance is weaker with this feature and therefore just has a
front crossing our area, while others have a more pronounced
wave along the front. Given the rather active upper air pattern
with many moving pieces, the guidance will likely continue to
show varying solutions. As a result, did not stray away from the
NBM which paints chance PoPs (around 30 percent) Saturday night
into Sunday morning. Any snowfall will depend on the wave
developing and also tracking close enough as a rather cold air
mass heads southward. Temperatures still below average, however
Sunday looks to be several degrees colder than Saturday.

For Monday...As the parent upper-level low starts to exit, the
center of arctic high pressure builds into our area during
Monday. This will result in a very cold day with temperatures
well below average. Any northwesterly breeze should be easing as
the high builds in more and therefore erodes the pressure
gradient. Another clipper system may then start to approach
Monday night, however this feature will depend on the upper-
level trough amplifying once again as the surface high starts to
weaken and shifts offshore.

&&

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

Today...VFR. Winds SSW 5 to 10 kt. High confidence.

Tonight...VFR. SSW winds 5 to 10 kt. High confidence.

Wednesday...Initially VFR. RA and/or SN developing between
15-18Z, with SN and MVFR restrictions most likely at KRDG/KABE.
SN changes to RA in the afternoon. Farther south, at least some
brief MVFR conditions possible after 18Z in RA. SSW winds 10 to
15 kt with 20 to 25 kt gusts (up to 30 kt gusts at ACY).
Moderate confidence.

Outlook...

Wednesday night...Conditions improve to VFR. Southwest to wind
gusts may gust to 20 knots at times.

Thursday...VFR. West-northwest wind gusts to around 25 knots.

Friday and Saturday...A period of sub-VFR conditions possible
with snow or rain, especially Friday night and Saturday morning.
Westerly winds may gust to about 20 knots on Saturday.

&&

.MARINE...
Sub-SCA conditions on all waters for today for winds 10 to 15
kt becoming south by late this afternoon.

South to southwest winds increase to 15 to 25 kt with gusts up
to 30 kt tonight. A SCA is now in effect for all waters for
tonight.

On Wednesday, VSBY restrictions in rain expected. A Gale Watch
is now in effect for the ocean waters for Saturday as southwest
winds will range from 20 to 30 kt with gusts up to 35 kt. For
Delaware Bay, winds will range from 15 to 25 kt with gusts up to
30 kt.

Outlook...

Wednesday night...Small Craft Advisory probable. Gale force
wind gusts possible, especially during the evening, and a Gale
Watch has been issued.

Thursday...Small Craft Advisory conditions gradually subside at
night.

Friday...The conditions may remain below Small Craft Advisory
criteria.

Saturday...Small Craft Advisory probable, with gale force wind
gusts possible.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory from 6 AM to 6 PM EST Wednesday for
     PAZ054-055.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 PM EST
     Wednesday for ANZ430-431.
     Small Craft Advisory from 6 PM this evening to 6 AM EST
     Wednesday for ANZ450>455.
     Gale Watch from Wednesday morning through Wednesday evening
     for ANZ450>455.

&&

$$

SYNOPSIS...Gorse
NEAR TERM...MPS
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Gorse/MPS/Staarmann
MARINE...Gorse/MPS/Staarmann