756
FXUS61 KPHI 212341
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
741 PM EDT Mon Sep 21 2026

.WHAT HAS CHANGED...
Aviation section updated for 00Z TAFs.

&&

.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 potentially significant tidal flooding
expected for this week. The first batch of Coastal Flood headlines
have been issued with more likely to come.

4. Dangerous rip currents and high surf are expected at the
Jersey Shore and Delaware Beaches. Significant beach erosion is
also likely.

&&

.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
stalling to our south, and remain there through Tuesday. It
continues to look like it will lift a little closer to our region
tonight 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.

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.

Confidence continues to increase that as a mid-level impulse tracks
eastward out of portions of the Midwest and Ohio Valley towards the
Eastern Seaboard, surface cyclogenesis will occur off the coast of
the Carolinas Tuesday into Tuesday night. The initial track of the
developing low is expected to be to the northeast, well offshore.
However, with a strong high centered over portions of Quebec, a
sharp pressure gradient over the region will at least lead to breezy
conditions through Thursday near the coast. It should remain mostly
dry through this period however.

Friday and beyond, significant uncertainty remains. Models now fall
into two relatively distinct camps, with one camp continuing to take
the low northeast and away from the region. The other camp has the
low deviating due northward or even northwestward to our region. The
EC ensembles are generally clustered fairly tightly near the
deterministic EC, which would favor this scenario. On the other
hand, the deterministic GFS has the low continuing northeastward and
the GEFS only has a few members bringing the low towards the coast.

Unfortunately, the difference in sensible weather outcomes between
these two scenarios is substantial. Should the low track
northeastward away from the region, any rain would be confined to
the immediate coast, if any, and winds would decrease quicker. A
track closer to the coast or even into the coast would lead to
potentially significant impacts from rain and wind. For now, PoPs
are maintained in the 20-40% range, and highest southeast of I-95.
It is worth noting that there are several members in the ensemble
suites which feature a middle ground scenario, where the low does
deviate some but still remains fairly comfortably offshore. This
scenario would lead to some impacts from rain and wind, but the
inland extent would be fairly limited. We will continue to monitor
trends closely as we try to nail down specific impacts and timing
over the coming days.


KEY MESSAGE 3...Multiple rounds of potentially significant tidal
flooding expected for this week. The first batch of Coastal Flood
headlines have been issued with more likely to come.

With a slow moving coastal storm increasingly likely, the threat for
tidal flooding has increased. Strong onshore flow that is projected
to last for several days will result in water piling up across tidal
tributaries and within back bays of coastal communities. Tidal
levels will also be enhanced with astronomical tides increasing with
the upcoming Full Moon on Saturday. This combination of factors will
lead to widespread tidal flooding, some of which could get to the
Moderate stage. While not currently forecast, the threat for major
flooding is not off the table, especially getting near the full
moon.

Minor tidal flooding begins as early as tomorrow afternoon and
evening for some locations. A Coastal Flood Advisory was issued for
Ocean, Atlantic, and Cape May County in New Jersey and Kent and
Sussex County in Delaware. For those same areas, tide levels are
expected to increase for Wednesday and Thursday, potentially getting
to Moderate stage. A Coastal Flood Watch was issued for Wednesday
and Thursday evening`s high tide. Moderate tidal flooding could even
continue into the weekend. As mentioned above, cannot rule out tide
levels reaching major, given the setup.

For the rest of the NJ coast north of Barnegat Inlet, tide levels
are currently forecast to reach Minor on Wednesday and Thursday.
Coastal Flood Advisories likely will be needed, but tide levels are
currently forecast to stay below Moderate at this time and lower
water levels than in areas in southern Delaware and South Jersey.
The same goes for the New Jersey side of Delaware Bay and tidal
Delaware River.

Widespread minor tidal flooding is not currently expected within the
Chesapeake Bay. Usually, strong northeast winds do not result in
tidal flooding in these areas.


KEY MESSAGE 4...Dangerous rip currents and high surf are
expected at the Jersey Shore and Delaware Beaches. Significant
beach erosion is also likely.

A coastal storm is expected to form offshore, resulting in
hazardous conditions along the coast. The surface low will
linger off our waters for multiple days, bringing strong winds
and high seas for our marine zones. By Wednesday, breaking
waves within the surf zone of 6 to 12 feet are expected. This
will continue through at least Friday with the coastal storm
currently progged to be right around the benchmark by the end of
this week. Dangerous rip currents will accompany that high
surf, making it extremely hazardous to enter the water at any
time this week. The high surf and strong winds could also result
in significant beach erosion for the Jersey Shore and Delaware
Beaches.

With high confidence in the rip current and high surf forecast,
the High Risk for life threatening rip currents was extended
through Friday for all beaches. A High Surf Advisory was issued
for all beaches as well from Wednesday through at least Friday,
when breaking waves within the surf zone will be around 10 feet
or higher.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight...Mainly MVFR across KILG/KMIV/KACY through the night
with other sites starting as VFR, but eventually changing over
to MVFR as northeasterly winds continue to prevail and usher in
low stratus around 06Z or so. Cannot rule out brief periods of
IFR vis or cigs mainly for KACY. Light showers overall with
more steady coverage across the southern terminals. Moderate
confidence.

Tuesday...MVFR. Some showers linger into late morning, mainly
south. Cannot rule out periods of IFR cigs at times.
Northeasterly winds around 10 kts prevail with 15-20 kt gusts.
Moderate confidence.

Outlook...

Tuesday night...Sub-VFR conditions are possible at times in rain and
low clouds, particularly for the southernmost terminals.

Wednesday through Thursday...There will likely be at least some
periods of VFR conditions, but low clouds and rain at times could
still lead to restrictions. Gusty northeast winds possible.

Thursday night through Saturday...A high degree of uncertainty
remains, but sub-VFR conditions will be possible. Gusty northeast
winds possible.

&&

.MARINE...
Small Craft Advisory conditions continue to develop on the Atlantic
Coastal Waters, and will develop by 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.

Tuesday night onwards, SCA conditions are expected with periods of
gales possible. Consequently, a Gale Watch remains in effect 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.

Throughout much of the period, high seas are expected and visibility
restrictions will be possible at times in rain.

Rip Currents...see Key Message 4.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Advisory from 4 PM to 10 PM EDT Tuesday for
     NJZ020-022>027.
     Coastal Flood Watch from Wednesday afternoon through late
     Thursday night for NJZ020-022>027.
     High Risk for Rip Currents from Tuesday morning through Friday
     afternoon for NJZ014-024>026.
     High Surf Advisory from 8 AM Wednesday to 6 PM EDT Friday for
     NJZ014-024>026.
DE...Coastal Flood Advisory from 4 PM to 10 PM EDT Tuesday for
     DEZ002>004.
     Coastal Flood Watch from Wednesday afternoon through late
     Thursday night for DEZ002>004.
     High Risk for Rip Currents from Tuesday morning through Friday
     afternoon for DEZ004.
     High Surf Advisory from 8 AM Wednesday to 6 PM EDT Friday 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 until 6 PM EDT Tuesday for ANZ450>455.
     Gale Watch from Tuesday evening through Thursday afternoon for
     ANZ450>455-480>483-485.

&&

$$

DISCUSSION...AKL/Cooper/Hoeflich
AVIATION...AKL/Cooper/MJL
MARINE...AKL/Cooper/Hoeflich