159
FXUS61 KPHI 160549
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
149 AM EDT Thu Jul 16 2026

.WHAT HAS CHANGED...
Updated aviation section for 6Z TAFs.

&&

.KEY MESSAGES...
1. Above normal temperatures will continue through Thursday,
with heat indices around 100 in the I-95 urban corridor.

2. Smoke from Canadian wildfires will infiltrate the area
beginning tonight through Thursday, and potentially lingering
through Friday into Saturday.

3. Isolated thunderstorms possible Thursday afternoon and
evening for Philly Metro and south.

4. The first half of the weekend is shaping up to be active and
unsettled with showers and thunderstorms expected for Saturday
into Saturday night. Some of these could be severe and also
produce heavy rainfall resulting in flash flooding.

&&

.DISCUSSION...
KEY MESSAGE 1...Above normal temperatures will continue through
Thursday, with heat indices around 100 in the I-95 urban
corridor.

A weak cold front passed through the area overnight, which will
knock down both temperatures and dew points a bit for later
today. While it will still be quite hot, with highs in the 90s,
heat indicies will only be a few degrees higher from the actual
air temperature. Also, have to consider how thick the smoke will
be in the area (see more on that below), which may limit
daytime heating on Thursday. Thus, went with a heat advisory for
the urban corridor where sensitivity is highest and criteria may
just be met (100 degrees). Elsewhere held off.

KEY MESSAGE 2...Smoke from Canadian wildfires will infiltrate
the area beginning tonight through Thursday, and potentially
lingering through Friday into Saturday.

The latest hi-res guidance continues to indicate near surface smoke
the wildfires in western Ontario will spread into the region
following tonight`s cold frontal passage. The smoke appears likely
to persist in the area through Thursday night, and potentially
lingering through Friday and Saturday as well. The smoke is
anticipated to result in visibility restrictions and potential for
poor air quality, but exactly to what degree this may be is
uncertain. This smoke event is not currently anticipated to be as
severe as the June 2023 event, but this will be difficult to predict
ahead of time.

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 3... Isolated thunderstorms possible Thursday
afternoon and evening for Philly Metro and south.

A lingering cold front bisecting the region Thursday may
provide a sufficient area of convergence to allow for another
round of isolated afternoon showers and thunderstorms to
develop. Uncertainty remains high, however, with hi res guidance
in disagreement on timing and coverage as well as the
positioning of the front. Furthermore, the presence of wildfire
smoke in the region will add another uncertain factor to the
mix. The upshot here is there is a limited conditional potential
for thunderstorm development Thursday afternoon and evening,
but should they develop, a few storms could pack some gusty
winds, similar to what occurred Wednesday afternoon. Along and
south of the front, some hi res ensemble members have SBCAPE
values in the 2000-2500 J/kg range once again along with 30 kts
of deep layer shear. Further more, forecast soundings also show
a setup for an inverted-V profile, which will be favorable for
downbursts in thunderstorms that can develop. At this time, the
best placement for the frontal boundary will be around the
Philly Metro/PA Turnpike/I-195 corridor with the best chance for
convective development along and south of the front.


KEY MESSAGE 4...The first half of the weekend is shaping up to be
active and unsettled with showers and thunderstorms expected for
Saturday into Saturday night. Some of these could be severe and also
produce heavy rainfall resulting in flash flooding.

We are still a few days out, but are monitoring the potential flash
flooding and severe weather setup as we get into the weekend.

As we get towards Friday night, low pressure will be approaching as
it moves into the Great Lakes region and pushes a warm front ahead
of it northwards towards the area. This could bring some showers and
storms into the area as early as the overnight period Friday night
with more widespread showers and storms expected for Saturday into
Saturday night as low pressure moves from the lower Great Lakes
eastward towards New England. As is often the case with these summer
patterns, there is some potential for both severe weather and heavy
rain/flash flooding. At this vantage point the shear looks to be
moderate to potentially strong with the main question being how
unstable it will get. This will determine the extent of any severe
weather threat but at this point we see at least some potential for
severe weather Saturday...especially during the afternoon and
evening. Precipitable water values will also be increasing to around
2+ inches. That is well above the 90th percentile for this time of
year, increasing the risk for heavy rain/flash flooding. It appears
storms may come through in multiple rounds with one or more rounds
of storms coming in later Friday night into the day Saturday with
the warm front and then another coming in late day into Saturday
night ahead of the cold front. So the bottom line is that Saturday
could be quite unsettled and most of the region has POPs in the 70-
90 percent range reflecting this.

As we head towards the latter part of the weekend, the latest
indications are for the cold front to move through a little faster
Saturday night into early Sunday. This will keep some chances for
showers/storms around into the first part of Sunday but but based on
this faster timing of the front, it looks like we will start to
clear out from NW to SE by the latter part of Sunday. As such, the
threat for severe weather and/or flash flooding appears low at this
time for Sunday.

High pressure builds in to start the new week before the next
frontal system may affect the area next Tuesday into Wednesday with
renewed chances for showers and storms.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Thru 12Z...Mix of VFR and MVFR due to wildfire smoke filtering
into the region. Winds generally northwest to north 5-10 kts.
Moderate confidence.

Today...MVFR visibilities likely through much of the day from
wildfire smoke. There are indications that some denser smoke
will arrive later in the day (which may cause IFR visibilities
at times), but more likely to hold off until night. Isolated
thunderstorms possible from KPNE south and east after 21Z, but
uncertainty remains high at this time, so just kept VCTS. West-
southwest winds around 10-15 kt with gusts up to 20 kt in the
afternoon. Moderate confidence overall.

Tonight...MVFR to possibly IFR as smoke thickens behind
secondary front. Any early evening TSRA should end by 02Z.
Winds northwest to north 5-10 kts. Low confidence.

Outlook...

Friday...Some restrictions possible due to lingering smoke from
the Canadian wildfires, especially early.

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

Sunday...Lingering showers/storms possible in the morning then
becoming mainly VFR by the afternoon.

Monday...VFR expected.

&&

.MARINE...
No marine headlines are in effect through Thursday. Southwest winds
around 10-15 kt through this evening will become north-northest
overnight around 5-10 kt following a frontal passage. Winds will
then become south-southwest again on Thursday around 10-15 kt. Seas
around 2-3 feet through Thursday.

Generally fair weather is expected, however wildfire smoke will
filter into the region tonight into Thursday. This may cause some
localized areas of visibility restrictions, however no marine dense
smoke advisories for this are warranted at this time.


Outlook...

Friday...Canadian wildfire smoke may cause visibility restrictions
at times. Otherwise, fair weather and no marine hazards anticipated.

Saturday through Saturday night...South to southwesterly winds could
approach advisory criteria, with 10-15 kt winds and gusts 20-25 kt.
Seas generally under 5 feet. Showers and thunderstorms likely. Smoke
may also linger some during this period potentially still causing
some visibility restrictions.

Sunday...No marine hazards currently anticipated with winds under 25
kts and seas under 5 feet. Scattered showers and thunderstorms
possible.

Monday...Fair weather expected with winds under 25 knots and seas
around 3 feet.

Rip Currents...

On Thursday, south to southwest winds will average 10 to 15 mph
with a light southeast swell with a period of 6 to 8 seconds.
Breaking waves will average 1 to 2 feet. As a result, there is a
LOW risk for the development of dangerous and life threatening
rip currents at the Jersey Shore and at Delaware Beaches.

On Friday, north winds around 10 mph in the morning will veer to
the southeast in the afternoon with a light southerly swell
with a period around 6 seconds. Breaking waves will average 1
to 2 feet. As a result, there is a LOW risk for the development
of dangerous and life threatening rip currents at the Jersey
Shore and at Delaware Beaches.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory from noon today to 8 PM EDT this evening for
     PAZ070-071-102-104-106.
     Air Quality Alert until midnight EDT tonight for PAZ054-055-
     060>062-070-071-101>106.
NJ...Heat Advisory from noon today to 8 PM EDT this evening for
     NJZ015-017>019.
DE...Heat Advisory from noon today to 8 PM EDT this evening for
     DEZ001.
MD...None.
MARINE...None.

&&

$$

DISCUSSION...Cooper/DeSilva/Fitzsimmons/Johnson/MJL/RCM/Staarmann
AVIATION...DeSilva/Fitzsimmons/MJL/RCM/Staarmann
MARINE...DeSilva/Fitzsimmons/MPS/Staarmann