507
FXUS61 KPHI 171035
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
635 AM EDT Fri Jul 17 2026

.WHAT HAS CHANGED...
Aviation section updated for 12Z TAFs.

&&

.KEY MESSAGES...
1. Smoke from Canadian wildfires will remain in the area today,
lingering into the weekend.

2. The first half of the weekend is shaping up to be active
with showers and thunderstorms expected for Saturday into
Saturday night along with warm and very humid conditions. Storms
have the potential of becoming severe and also producing heavy
rainfall leading to flash flooding.

&&

.DISCUSSION...
KEY MESSAGE 1...Smoke from Canadian wildfires will remain in
the area today, lingering into the weekend.

Latest HRRR/RAP smoke guidance continues to depict that a slug of
dense near surface smoke from the wildfires originating over western
Ontario will remain in the area through Saturday. Skies will
likely be quite hazy with visibilities projected to fall between
1 to 3 miles this morning, especially southern areas. With more
of a northerly surface flow expected today, this may suppress
the worst of the smoke south of our area by mid-day. However, as
flow shifts to more southerly by tonight, guidance suggests
that surface smoke works back north tonight into Saturday.

So far this smoke event has not reached the levels of June 7
2023, but some areas have gotten relatively close. Its certainly
the smokiest event since then.

Latest guidance is optimistic about smoke clearing out Saturday
night.

For more information about air quality in your area, visit your
state Department of Environmental Protection agency. We will
also relay any Air Quality Alerts they may issue on our website.


KEY MESSAGE 2...The first half of the weekend is shaping up to
be active with showers and thunderstorms expected for Saturday
into Saturday night along with warm and very humid conditions.
Storms have the potential of becoming severe and also producing
heavy rainfall leading to flash flooding.

Low pressure will move eastward through the Great Lakes region
Friday night through Saturday before passing by to our north
Saturday night into early Sunday. As this occurs, expect
multiple rounds of showers and thunderstorms to move
through...first with the warm front and then with the cold
front.

At this point it looks like conditions stay mainly dry through
most of Friday night. Heading into Saturday, the warm front
lifts through in the morning and this will bring an initial
round of showers and storms through the area. This first round
should especially target areas near and north of the urban
corridor where POPs are 70-90 percent. Parts of south Jersey and
southern Delmarva could largely miss this initial round. There
will be a threat for heavy rainfall potentially leading to flash
flooding with the morning storms but the severe weather risk
looks more limited until later. Following this first round,
there could be a break of a few hours in the afternoon during
which it will get quite muggy. Highs should range from the low
80s north to the low 90s south but with very high dew points
expected the heat indices are likely to top out in the mid and
upper 90s around the urban corridor and up to around 105 across
portions of Delmarva. So heat headlines may be needed.

As we get into the mid to latter part of Saturday afternoon
into the evening another round of heavy showers and storms looks
to move through ahead of the cold front. It`s with this round
that we`ll see the best chance of severe weather and flash
flooding as well. In terms of the parameters, ML CAPE looks
likely to top out in the 1000- 2000+ j/kg range with deep layer
shear around 35 to 50 knots. This will support a threat for
damaging winds and even some potential for supercells which, if
these occur, could also produce large hail. PWATs will also be
surging to over 2 inches (well above the 90th percentile for
this time of year) so there`s an increasing potential for very
heavy rainfall leading to flash flooding. The greatest threat
for this will be for urban, low lying areas, and areas near
creeks and streams. Also, any locations that get especially hit
hard by both rounds of convection will have a greater potential
for flash flooding. Rain amounts of over 2 inches per hour will
be possible.

Shower/storms should weaken by the late evening into the
overnight Saturday night as the cold front moves through. Sunday
is now shaping up to be largely dry with seasonable
temperatures and comfortable humid levels. Only our southern
most zones over portions of the MD eastern shore, southern
Delaware, and far southern NJ have chances for some lingering
showers or storms but even here the POPs are only 20-30 percent.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Today...MVFR/IFR VSBYs in the morning, improving to MVFR, then
possibly to VFR by the afternoon as smoke clears out briefly,
especially northern terminals. LGT/VRB winds in the morning,
becoming W 5 to 10 kt, except at KACY, where winds will become
SE behind afternoon sea breezes. Low confidence.

Tonight...MVFR/IFR vsby return as smoke starts regressing back
northward. Winds shift more southerly but remain fairly light.
Low confidence.

Outlook...

Saturday through Saturday night...At least some restrictions
likely at times due to showers and storms, and possibly due to
smoke early Saturday.

Sunday...Mainly VFR except some lingering showers possible at MIV
and ACY especially early in the day which could still cause some
restrictions for these sites.

Monday...VFR expected.

Tuesday...Potential for some restrictions by late day and at night
as the next system approaches with shower/storms.

&&

.MARINE...
No marine headlines are in effect through early Saturday.
North- northeast winds around 10 kt are expected this morning,
before settling out of the southeast in the afternoon. Seas
around 2-3 feet through early Saturday.

However, wildfire smoke will continue to filter into the region
through early Saturday. This may cause localized areas of
visibility restrictions. Will have to monitor observations
closely as denser smoke passes through the region, where marine
dense smoke advisories may become warranted if visibilities
drop to 1 mile or less, but at this time it appears more
unlikely.

By Saturday winds shift more south-southwest and increase ahead
of a strong cold front. SCA`s may be needed as gusts may reach
30 kts with seas above 5 feet. Showers and thunderstorms will
become increasingly likely as well.

Outlook...

Saturday night...South to southwesterly winds near or above SCA
criteria expected. Expect winds around 15-20 kt with some gusts
20-30 kt. Seas likely 4-6 feet. Showers and thunderstorms
likely.

Sunday...Seas may linger near SCA levels early in the day but
otherwise the conditions should be sub SCA.

Monday...Fair weather expected with winds under 25 knots and seas
around 2-4 feet.

Tuesday...Winds and seas may approach SCA levels by late day.


Rip Currents...

Today, north-northeast winds around 5 to 10 mph in the morning
will settle out of the east-southeast in the afternoon with a 1
to 2 foot swell around 8 to 9 seconds. Breaking wave heights
will range between 1 to 2 feet. As a result, there is a LOW risk
for the development of dangerous rip currents at both the
Jersey Shore and Delaware Beaches.

On Saturday, south winds around 10 to 15 mph in the morning,
will increase to 15 to 30 mph late in the afternoon with a 2 to
3 foot swell around 9 seconds. Breaking wave heights will range
between 2 to 4 feet. As a result, have opted to go with a
MODERATE risk for the development of dangerous rip currents at
both the Jersey Shore and Delaware Beaches. Would not be
surprised if an upgrade to HIGH will become necessary for some
spots along the Jersey Shore.

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

&&

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

&&

$$

DISCUSSION...DeSilva/Fitzsimmons/MPS/RCM
AVIATION...DeSilva/Fitzsimmons/MPS/RCM
MARINE...DeSilva/Fitzsimmons/RCM