019
FXUS61 KPHI 161019
AFDPHI

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

.WHAT HAS CHANGED...
Updated aviation section for 12Z 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
today, potentially lingering into Friday.

3. Isolated severe thunderstorms possible this 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 today, potentially lingering into Friday.

The latest hi-res guidance continues to indicate near surface
smoke the wildfires to the north and northwest will spread into
the region following the overnight cold frontal passage. The
smoke appears likely to persist in the area through tonight,
and potentially lingering into Friday 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.

Latest guidance is a bit more optimistic about the smoke
clearing out somewhat on Friday.

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 severe thunderstorms possible this
afternoon and evening for Philly Metro and south.

A lingering cold front bisecting the region today may provide a
sufficient area of convergence to allow for another round of
scattered 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 this afternoon and evening, but should
they develop, a few storms could pack some gusty winds, similar
to what occurred yesterday 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. The SPC has
highlighted this region and points south in a MARGINAL (1 out of
5) risk of severe weather today.

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 /10Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

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 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 03Z.
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 Friday. North-
northest winds around 5-10 kt this morning becoming south-
southwest later today around 10-15 kt. Winds then shift back to
a more northerly direction tonight into Friday, but remaining
less than 15 kts. Seas around 2-3 feet through Friday.

Generally fair weather is expected, however two flies in the
ointments are present. Late today into this evening, scattered
showers and isolated thunderstorms, a few of which may be gusty,
are possible. In addition, wildfire smoke will filter into the
region today and tonight. 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 SCA criteria, with 15 kt winds and gusts 20-25
kt. Seas may reach 5 feet. Showers and thunderstorms likely.

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...

Today, 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/RCM/Staarmann