302
FXUS61 KPHI 111849
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
249 PM EDT Mon Aug 11 2025

.SYNOPSIS...
High pressure will continue to shift more to our east through
Tuesday. A surface trough across our area Wednesday gives way to a
cold front settling across our area from the northwest during
Thursday. The front may stall near Delmarva Friday before
dissipating into Saturday. High pressure arrives for Saturday and
Sunday, then a cold front will approach from the northwest on Monday.

&&

.NEAR TERM /THROUGH TUESDAY/...
Fair weather will continue for the rest of today as high
pressure has shifted offshore, but still controls the weather.
There has been an increase in expected cloud cover for southern
areas, especially Delaware and eastern Maryland. Otherwise, it`s
mostly clear and warm for the rest of the area.

For tonight, fair weather will begin the period, however, later
in the overnight as temperatures cool, dewpoints rise, and winds
become light, some low clouds and areas of fog will likely
develop. We do not expect much widespread dense fog, so no
advisory is expected at this time. However, there could be some
patchy thicker fog, especially for southern New Jersey.

On Tuesday, the clouds and fog will lift a few hours after
sunrise, then some clouds will likely remain around for much of
the day. With high pressure to our south and east, return flow
will remain across the area, leading to an increase in
temperatures and humidity values. However, Heat Index values
will remain below advisory levels.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As our region will be well southeast of an upper-level trough in
central Canada Tuesday night, the low-level moisture is forecast to
increase. While some high clouds may start to increase, there will
be the potential for stratus and/or some fog to develop overnight
within the light south to southwest flow as deeper moisture arrives.
The combination of some clouds and higher dew points will help keep
our overnight temperatures warmer, with lows forecast to be in the
mid/upper 60s to low 70s.

The aforementioned upper-level trough will shift eastward across
eastern Canada Wednesday and just glance our area. A cold front will
start to approach late Wednesday, however a surface trough in place
looks to provide an axis for some low-level convergence. There
should be enough focus for some convection to develop within an
unstable and very moist air mass. The greatest coverage of showers
and thunderstorms looks to be across or western zones during the
afternoon. Given a slowly approaching front and precipitable water
values to around 2 inches, any stronger convection that develops and
is sustained, especially near the surface trough, will be capable of
producing localized very heavy rain. Much of the convection as it
shifts eastward Wednesday afternoon should weaken Wednesday night
given the weak forcing. While the day may start with some areas of
stratus and/or fog, high temperatures Wednesday will be in the upper
80s to low 90s with dew points in the low 70s. Peak heat indices are
forecast to be in the 90s for nearly the entire area, thus remaining
below heat advisory criteria.

As we go through Thursday, a weak cold front is forecast to settle
southward across our area. Much in the way of forcing and focus for
convective development looks to be weak despite a very warm/hot and
humid air mass in place. Some convection cannot be ruled out given
the front moving through, however the probabilities are low at about
30 percent. High temperatures are forecast to be around 90 degrees
for most of the area. Dew points starting in the lower 70s ahead of
the front should then tend to decrease some from the northwest
during the course of the day, although this will depend on the
timing of the actual front and southward push of the drier air.
Heat indices are forecast to peak below 100 degrees across the
region.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Summary...Warm/hot and humid; Some very low chances for showers and
thunderstorms at times.

Synoptic Overview...The flow aloft is forecast to be more zonal
Friday into Saturday as an east to west ridge to our south tries to
expand northward some. An upper-level trough however moving across
eastern Canada over the weekend and early next week may push the
northern part of the ridge southward. At the surface, a weak cold
front may stall across Delmarva Friday before dissipating into
Saturday. The next cold front approaches from the northwest during
Monday.

For Friday....As the flow aloft becomes more zonal, lingering
ridging initially across parts of eastern Canada will support
surface high pressure sliding by to our north. This should assist in
pushing a weak cold front down across Delmarva where it should stall
before starting to dissipate. We have more of the influence of the
surface high to our north, however there is no significant push of
cooler air. The dew points are forecast to come down some with
enough drier air mixing in especially during the daytime hours. Not
anticipating any convection given the rather weak lingering front
near Delmarva for a time and a lack of forcing. High temperatures
outside of the coastal areas and higher elevations are forecast to
be in the upper 80s to low 90s. The dew points look to range from
the upper 50s across the far north to around 70 across Delmarva.

For Saturday and Sunday...Our region is forecast to be on the
northern side of a strong west to east ridge aloft. An upper-level
trough moving across eastern Canada though looks to weaken the
northern edge of the ridge especially on Sunday across the Northeast.
This will result in the heights lowering a little, however given the
stronger part of through is well to our north our temperatures
should not be impacted much. As a result, the warm to hot conditions
are forecast to continue with daytime highs reaching the low 90s for
may areas. It will be humid as well, although the dew points are
anticipated to lower enough during peak heating to keep heat indices
below heat advisory criteria. Other than an isolated shower or
thunderstorm possible mainly well inland and across the higher
elevations each afternoon, the probability of convection is
currently looking to be very low.

For Monday...The aforementioned upper-level trough, most pronounced
well to our north, is forecast to send a cold front into our area
during this time frame. Given the dynamics are currently forecast to
be passing by well to our north, the forcing and low-level
convergence looks to be meager with the incoming cold front. This
may also result in the front not getting all that far south with
time. Given increased uncertainty with the details this far out in
time, made no changes from the NBM which has 20-30 percent chances
for showers and thunderstorms across our area.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Rest of Today...VFR conditions will continue across the area.
South to southwest winds 5-10 knots expected. High confidence.

Tonight...Conditions will begin VFR for all areas, before
lowering to MVFR, even IFR in some area late in the overnight
and toward daybreak Tuesday. Winds will become light and
variable through this evening and overnight. High confidence in
overall forecast, lower confidence on how low conditions become.

Tuesday...MVFR to IFR conditions begin today, but will begin to
lift a couple of hours after sunrise. All sites should return to
VFR by 14z-16z. Light and variable winds early become south-
southwest 5-10 knots. High confidence overall, lower confidence
in timing.

Outlook...

Tuesday night...Some low clouds/fog possible overnight.

Wednesday and Thursday...Some low clouds/fog possible to start
Wednesday morning, then mostly VFR. Some showers and thunderstorms
should occur, especially Wednesday afternoon and evening, with local
sub-VFR conditions.

Friday and Saturday...VFR overall.

&&

.MARINE...
No marine headlines are anticipated through Tuesday. Winds will
generally be out of the south/southwest under 15 kt. Seas 2-3
feet.

Outlook...

Tuesday night through Saturday...The conditions are anticipated to
be below Small Craft Advisory criteria.

Rip Currents...

For today, south-southeast winds around 10 mph with breaking
wave heights of 2-3 feet. Easterly swell around 2 feet at 7-9
seconds in length. We are also still within two days of the
full moon. Will continue with a MODERATE risk for the development
of dangerous rip currents at all beaches.

For Tuesday, southerly winds increases to 10-15 mph, with a 7-9
second period easterly 2 foot swell continuing. As a result,
breaking waves in the surf zone look to remain 1-3 feet. At
this time, will continue to maintain a MODERATE risk for the
development of dangerous rip currents at all beaches.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Air Quality Alert until 11 PM EDT this evening for NJZ001-
     007>010-012-015.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Gorse
NEAR TERM...Robertson
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Gorse/Robertson
MARINE...Gorse/MJL/Robertson