771
FXUS61 KPHI 210925
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
525 AM EDT Mon Sep 21 2026

.WHAT HAS CHANGED...
Increasing confidence of gale conditions during the second half
of the week.

Models are in slightly better agreement on the track of the
late week coastal low, though there remains uncertainty in its
evolution from Friday onward.

There is increasing confidence in the details of the coastal
flood and rip current risks through the first half of the week.

&&

.KEY MESSAGES...
1. A frontal boundary south of the region will keep rain
chances around through mid-week, especially across southern
portions of the area.

2. A closed mid-level low ejecting from the Ohio Valley is
expected to lead to the development of a surface low off the
Eastern Seaboard during the middle and latter parts of this
week. Depending on the track of the low, it could bring
increased rainfall chances to the region.

3. Multiple rounds of tidal flooding are expected later this
week, with tidal flooding potentially beginning as early as
Tuesday evening.

&&

.DISCUSSION...
KEY MESSAGE 1...A frontal boundary south of the region will
keep rain chances around through mid-week, especially across
southern portions of the area.

The cold front that crossed through our region Sunday Night is
expected to stall to our south today, and remain there through
Tuesday. It continues to look like it will lift a little closer
to our region Monday Night into Tuesday morning as a warm
front, but remain just south of the area. Due to the closer
proximity, and a mid level short wave trough, mean that that
period will have the highest chance for rain across our region.
Given that our low will be on the cool side of the front,
showers are going to be the main mode of any precipitation.
However, isolated, embedded thunderstorms will be possible over
Delmarva, particularly during the day on Tuesday.


For Wednesday into Thursday, the front should again be on the
move southward, lessening rain chances across the area.

Confidence is high that temperatures will be below normal
starting Tuesday. In fact, temperatures will likely struggle to
get out of the 60s areawide through most of this week.


KEY MESSAGE 2...A closed mid-level low ejecting from the Ohio
Valley is expected to lead to the development of a surface low
off the Eastern Seaboard during the middle and latter parts of
this week. Depending on the track of the low, it could bring
increased rainfall chances to the region.

Most of the models came into better agreement on the track and
the evolution of the coastal low through Thursday. Through this
time, the center of the low should stay far enough off shore
that rain chances across our region will be very low, except at
immediate coastal areas. However, it looks to be a deep and
intense low, so expect a large pressure gradient, even for
inland areas, and thus breezy to windy conditions. For coastal
areas, we could get close to wind advisory thresholds,
particularly later in the day on Wednesday through Thursday.

Friday into the weekend, some models have this becoming a cutoff
low and retrograding eastward. Notably though, this solution is
primarily with the deterministic, physical equation models.
Several ensemble members and some of the main AI models depict
this low continuing northeastward. All that being said, the
forecast, particularly the rain and wind forecast, is very
uncertain from Friday onward.

KEY MESSAGE 3...Multiple rounds of tidal flooding are expected
later this week, with tidal flooding potentially beginning as
early as Tuesday evening.

There will be a prolonged period of onshore flow at the coast
continuing through at least Thursday, and may continue through
the weekend. This, combined with increasing astronomical tides
ahead of the full moon on Saturday, means that multiple rounds
of tidal flooding for the Atlantic coast, Delaware Bay, southern
Raritan Bay, and tidal Delaware river are likely.

With the latest guidance, the earliest that we may see minor
tidal flooding is with the Tuesday afternoon/evening high tide,
and that appears most likely for the Atlantic coast and
Delaware Bay from Barnegat Inlet southward. That being said,
there remains uncertainty in how high the tidal anomalies will
be by Tuesday Afternoon.

The highest confidence in tidal flooding occuring is Wednesday
and Thursday. Through this period, we could even see moderate
tidal flooding.

Of special note with this set up, the prolonged nature of the
onshore flow tends to result in the highest tidal anomalies on
back bays, instead of ocean front. Consequently back bays
including Barnegat Bay and Shrewsbury River in New Jersey and
the Indian River Bay in Delaware could see the worst impacts
with this tidal flooding.

Friday into the weekend, there is considerably less confidence,
as it will be highly dependent on how the coastal low evolves
through this period. If the low retrogrades closer to the coast
as some models are showing, the coastal flooding is likely to
continue through the weekend.

For the Chesapeake Bay, the expected wind direction tends to
limit tidal flooding concerns, but it will need to be watched if
persistent easterly flow at the mouth of the Chesapeake.
Currently, tidal flooding is unlikely through Wednesday Night.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

For KPHL, KPNE, KILG, KTTN, KABE, and KRDG...Expect prevailing
VFR conditions through the day. MVFR ceilings may linger as late
as 15Z for KPHL, KILG, KPNE, and KTTN, but are expected to lift
this morning. Near or after 00Z, more MVFR ceilings, and an
additional round of rain will likely move through the region.
Once the MVFR ceilings move in, expect that to be the
controlling factor in flight category through Monday Night.
Northeasterly winds around 10kt, though occasional gusts up to
20 kt will be possible.

For KMIV and KACY...Expect some temporary breaks to VFR
conditions through the morning. However, as the winds become
more northeasterly, MVFR and even IFR ceilings will move back in
to the region, especially after 21Z. Northeasterly wind gusts at
or just above 20kt will be possible.


Outlook...

Tuesday...Sub-VFR conditions likely in periods of rain and low
clouds.

Wednesday through Friday...While uncertainty is high, sub-VFR
conditions will remain possible at times in rain or low clouds.
Gusty northeast winds are possible.

&&

.MARINE...
Small Craft Advisory conditions are expected starting early to
mid afternoon on the Atlantic Coastal Waters, and Tuesday
Morning for the Delaware Bay. Even though this is an unusual
wind direction for SCA conditions on the Bay, multiple models
depict a several hour period of wind gusts at or above 25 kt, so
have issued the SCA for the Bay from Tuesday morning through
Tuesday Night.

Gales are looking increasingly likely for at least a period of
the mid to late week. Consequently, a gale watch has been issued
for all of the Atlantic forecast zones starting Tuesday Evening,
and for the Delaware Bay starting Wednesday Morning. The watch
currently goes through the day on Thursday, when we have the
most confidence in gale conditions.

Gale conditions may linger into Friday and Saturday depending on
the evolution of the coastal low, which is uncertain in this
time frame.

Rip Currents...

Monday... There is a MODERATE risk for dangerous rip currents
Today thanks to the onshore component of the persistent
northeasterly winds. Breaking waves in the surf zone will be
around 2 to 4 feet.

Tuesday...Northeasterly winds strengthen to 20 to 30 mph with
wave heights in the surf zone building to 3 to 5 feet. As a
result, there is a HIGH risk of rip currents both for the New
Jersey shore and the Delaware Beaches.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...High Risk for Rip Currents from Tuesday morning through Tuesday
     evening for NJZ014-024>026.
DE...High Risk for Rip Currents from Tuesday morning through Tuesday
     evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory from 5 AM Tuesday to 6 AM EDT Wednesday
     for ANZ430-431.
     Gale Watch from Wednesday morning through Thursday afternoon
     for ANZ430-431.
     Small Craft Advisory from 11 AM this morning to 6 PM EDT
     Tuesday for ANZ450>455.
     Gale Watch from Tuesday evening through Thursday afternoon for
     ANZ450>455-480>483-485.

&&

$$

DISCUSSION...Cooper/Hoeflich/WFO PHI
AVIATION...Cooper/Fitzsimmons/WFO PHI
MARINE...Cooper/Fitzsimmons/WFO PHI