192
FXUS61 KPHI 170712
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
312 AM EDT Fri Oct 17 2025

.SYNOPSIS...
High pressure will gradually settle over our area tonight as it
weakens, then it quickly shifts offshore on Saturday. A strong cold
front crosses our area Sunday night, followed by high pressure
briefly building in for Monday night and Tuesday. The next cold
front moves through Tuesday night, then high pressure builds to our
south during Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
For today, the center of high pressure builds into the Ohio River
valley and Appalachian Mountains, just to the west of our region.
The day will be less breezy as a result, with winds remaining
around 10 mph, with a few gusts up to 20 mph possible. Conditions
will remain dry with highs reaching into the low-mid 60s for
most locations. With dew points remaining in the low 30s, minimum
RHs will be in the low-mid 30% range. However, given the lighter
breeze, fire weather concerns should remain low.

Skies will be mostly clear tonight and winds will become light
overnight. If temperatures end up a couple of degrees cooler
than forecast, then there would be a chance of some frost for
some areas. However, dewpoints slightly may begin to rise during
the evening and overnight, and some clouds may begin to filer
in late, which may slow down significant radiational cooling.
This will be something worth keeping and eye on. For now, lows
are expected to be in the mid 30s to low 40s with mid-40s across
the Philly metro and down the shore.


&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
A narrow ridge aloft is forecast to quickly shift offshore later
Saturday, taking surface high pressure with it. This is in response
to a sharpening upper-level trough across the Midwest and Plains. A
return flow will start to occur by later Saturday with warm air
advection eventually strengthening. Some increase in at least some
high clouds should occur well ahead of the aforementioned trough,
and also the development of a weak warm front to our southwest.
Afternoon high temperatures on Saturday are forecast to be warmer
than Friday. As the warm air advection continues Saturday night
along with some additional high clouds, temperatures are forecast to
be noticeably milder compared to the previous couple of nights.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Summary...A strong cold front moves through Sunday night, then
another cold front arrives Tuesday night.

Synoptic Overview...A strong upper-level trough is forecast to cross
the Northeast and Mid-Atlantic regions Sunday night and Monday. This
drives surface low pressure across the Great Lakes to adjacent
Canada with its strong cold front crossing our area Sunday night.
The low looks to occlude and a secondary low may develop along the
triple point near our area as the trough aloft may take on a
negative tilt. A narrow ridge aloft slides across our area Tuesday,
then another upper-level trough arrives Tuesday night through
Thursday along with an associated cold front Tuesday night.

For Sunday and Monday...A strong upper-level trough is forecast to
slide across the region during this time frame. While the guidance
is in good agreement with the arrival of this trough, there remains
especially some strength differences. Some guidance is stronger with
a closed low traversing our area, which favors a more organized
triple point surface low development. Given the strength of this
trough, southerly flow will increase ahead of it and that will peak
the warm air advection with many areas getting into the 70s on
Sunday despite an increase in cloud cover. The southerly flow will
result in moisture advection with surface dew points rising to near
60F during the day Sunday and also Sunday night ahead of the cold
front. The timing of the cold front Sunday night however is not
ideal for maximized instability, and the model consensus is that
instability is meager at best. Some model soundings show a little
low/mid level instability developing ahead of the cold front Sunday
night, however as of now this would not be enough to support
thunder. Given the strength of the trough, especially if it does
take on a negative tilt, forcing for ascent would be enhanced for a
time. As of now, looks like an area of showers arrive ahead of and
with the cold front Sunday night. The southerly flow at 925 mb is
forecast to increase to 40 knots which would increase the low to mid
level shear ahead of the cold front. This along with stronger
forcing may favor a narrow band of heavier showers that could
produce brief strong wind gusts (low CAPE/high shear environment).
The front shifts to our east to start Monday, however some lingering
cyclonic flow and colder air aloft could keep a few showers going
through Monday.

For Tuesday through Thursday...A narrow mid level ridge looks to
quickly slide across our area Tuesday along with surface high
pressure tracking to our south. Some warm air advection ahead of a
cold front will boost afternoon high temperatures Tuesday to near 70
degrees for many spots. The next upper-level trough from the Midwest
and Great Lakes to adjacent Canada shifts eastward with a cold front
crossing our area Tuesday night. The parent low may track rather far
to our north with the upper-level trough center, therefore it is
more uncertain on the details for our area regarding precipitation
chances. A larger upper-level trough across much of eastern Canada
Thursday would tend to maintain cyclonic flow across our area and
thus cooler air.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of tonight (through 12Z)...VFR/SKC. Northwest winds around
10 kt. High confidence.

Today...VFR. Northwest winds around 10 kt with gusts 15-20 kt possible
through the early afternoon, diminishing after 19z-20z. High confidence.

Tonight...VFR. Northwest winds around 5 kt or less. High confidence.

Outlook...

Saturday...VFR.

Sunday and Monday...Sub-VFR conditions probable Sunday night into
Monday due to showers and low clouds. Southerly wind gusts to around
25 knots during the day Sunday, shifting to westerly Monday.

Tuesday...Mainly VFR. An afternoon/evening shower possible.

&&

.MARINE...
SCA conditions gradually subside today as winds and seas begin
to decrease. Conditions subside first on the Delaware Bay and
the Atlantic Ocean waters north of Manasquan Inlet, lingering
longest for the coastal waters south of Manasquan Inlet. Fair
weather outside of SCA conditions.

Outlook...

Saturday...The conditions are anticipated to be below Small Craft
Advisory criteria.

Sunday and Monday...Small Craft Advisory conditions probable.

Tuesday...Wind gusts at times may be near Small Craft Advisory
criteria (25 knots).

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ430-
     431.
     Small Craft Advisory until noon EDT today for ANZ450.
     Small Craft Advisory until 6 PM EDT this evening for
     ANZ451>455.

&&

$$

SYNOPSIS...Gorse
NEAR TERM...MJL
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Gorse/MJL
MARINE...Gorse/MJL