660
FXUS61 KPHI 171917
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
317 PM EDT Fri Oct 17 2025

.SYNOPSIS...
High pressure will be in control through Saturday night. A
strong cold front crosses through the region late Sunday night
into Monday, followed by weak high pressure returning by Monday
night and Tuesday. Another cold front quickly passes through on
Tuesday night while another area of high pressure builds in from
the south on Wednesday through the end of the week.

&&

.NEAR TERM /THROUGH SATURDAY/...
High pressure will continue to build towards the east across the
region through Saturday. Modestly gusty winds will quickly fall
off this evening as the boundary layer decouples and sets up a
radiational cooling evening. Clouds trying to move in from the
northwest have been quick to erode as they run into dry air
over the region and this should result in a mostly clear
evening. However, there is some moisture around 700mb that does
looks to track through the area overnight bringing the potential
for some light cloud cover. This should act to limit how strong
the radiational cooling ends up so the forecast remains for
min temps falling into the low 40s and mid to upper 30s for the
higher elevation locales in the Poconos. MOS guidance does
suggest that some of the typically colder locations of the
Lehigh Valley and the NJ Pine Barrens could drop into the upper
30s however that will be cloud cover dependent.

Should those temps be met, frost is possible in some of those
areas so those with sensitive vegetation should take precautions
in case of a potential frost. Further north, the frost/freeze
program has already been ended due to the existence of a
previous freeze.

For Saturday, the ridge of high pressure will build then quickly
exit with light variable winds, partly cloudy skies and temps
warming into the mid to upper 60s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
A brief upper level ridge will slide across the region on Saturday
night, followed by a strong upper-level trough that is forecast to
cross the Northeast and Mid-Atlantic regions Sunday night into
Monday. This drives a surface low to track across the Great Lakes
then up towards Hudson Bay with its strong cold front crossing
through our neck of the woods on Sunday night. The primary low
then looks to occlude as a secondary low develops along the
triple point as a closed upper low cuts off from the parent
upper trough within close proximity to the area.

Given that the strength of this trough is quite strong, southerly
flow is expected to be enhanced out ahead of the front which
will allow a strong ramp up in warm air and moisture advection.
Despite cloud cover increasing late Saturday night and more so
on Sunday, it is anticipated that temperatures which be
noticeably warmer than days prior. Lows Saturday night will be
in the mid 40s to mid 50s with high temperatures on Sunday
topping out in the 70s with dew points getting up into the low
60s. While this would be typical for some convection to occur,
the timing of the cold front is not optimal to tap into the
greatest instability. In fact, many forecast soundings in the
short range only suggest ~500 J/kg of CAPE available and even
that may be generous. Regardless, convection will be ongoing on
Sunday upstream as there will likely be a squall line of some
sorts tracking across eastern Ohio and western Pennsylvania on
Sunday afternoon. For now, it does appear that most of Sunday
will be dry, with some showers possible late in the day. By
Sunday night, this line should advance into our area coming
through during the overnight hours. However as mentioned above,
the timing of the front passing through overnight will hinder
the thunderstorm threat. While an isolated rumble of thunder is
possible as the secondary low develops near the triple point, it
appears that a narrow band of heavier showers is the most
plausible outcome. Within this band could be brief period of
strong wind gusts up to 50 mph but anticipate that this activity
should remain below severe thresholds. Rainfall totals will
mostly range between 1/4-3/4 of an inch for most, with up to 1
inch possible up in the Lehigh Valley, Poconos and northern New
Jersey. Isolated higher amounts are possible.

The cold front will move east of the area on Monday resulting in
some drier conditions. However, as the area will remain under
cyclonic flow and in a cold air advection regime, suspect that a few
post-frontal showers are possible especially across northern areas.
Temperatures will return to more seasonable levels as clouds begin
to depart with highs in the low to mid 60s. Northwest winds will be
gusty behind the front with gusts approaching 30-35 mph at times.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
In wake of the front, high pressure briefly builds in from the south
for Monday night and Tuesday. Surface flow will begin to shift more
southerly overnight and into Tuesday, welcoming another brief period
of warm air advection. The next upper level trough will be quickly
approaching though, where the next cold front is on pace to cross
through the region late Tuesday night causing another round of
showers to occur. Behind this front, will be a broad but more
expansive area of high pressure that settles over the Deep South.
This should allow conditions to dry out again for Wednesday and
Thursday before another weak disturbance arrives on Friday, yielding
another chance for showers to occur.

Temperatures during the long term period will be warmest on Tuesday
ahead of the cold front where MaxT`s may reach into the low 70s.
Otherwise, the rest of the week appears to be cool in a post-frontal
regime where temps during the day will be limited to the 50s and 60s
with lows in the 40s.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of Today...VFR. Northwest winds around 10 kt with gusts
15-20 kt possible through the early afternoon, diminishing after
by 20-22z. High confidence.

Tonight...VFR. Northwest winds around 5 kt early, becoming light
and variable for most places overnight. High confidence.

Saturday...VFR. Light and variable winds early, shifting to
southwest around 5 knots by the afternoon. High confidence.

Outlook...

Saturday night through Sunday...VFR with an increase in clouds. A
chance for showers during the afternoon for KRDG and KABE, otherwise
dry. Gusty southerly winds up to 25-30 kt possible on Sunday.

Sunday night through Monday...Primarily VFR expected with areas of
sub-VFR possible, especially Sunday night. Showers likely which may
be heavy at times. Gusty winds between 20-30 kt possible.

Tuesday through Wednesday...Primarily VFR with sub-VFR conditions
possible Tuesday night. A chance of showers on Tuesday night.

&&

.MARINE...
Sub SCA conditions expected through the period with winds
generally northwest to northerly winds 10-15kts with an
occasional gust to 20kts and seas 3-4 feet.

Outlook...

Saturday night...No marine headlines expected. Fair weather.

Sunday through Monday night...SCA conditions likely with gusts up to
30 kt and seas up to 8 feet. Showers likely on Sunday night and
Monday.

Tuesday through Wednesday...SCA conditions possible with gusts up to
25 kt and seas around 4-6 feet. Showers possible Tuesday night.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...DeSilva/Gorse
NEAR TERM...Deal/MJL
SHORT TERM...DeSilva/Gorse
LONG TERM...DeSilva/Gorse
AVIATION...DeSilva/Gorse/MJL/Robertson
MARINE...Deal/DeSilva/Gorse/MJL