159
FXUS61 KPHI 192337
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
737 PM EDT Sat Jul 19 2025

.SYNOPSIS...
A cold front will approach and move through the region Sunday.
In its wake, high pressure builds in over the area through
Wednesday. Unsettled weather will return towards the end of the
week when another cold front approaches our region.

&&

.NEAR TERM /THROUGH SUNDAY/...
Our area is currently feeling the effects of weak ascent ahead of a
warm front approaching from the southwest. Isentropic ascent
overspreading the region has allowed for the development of
scattered showers. Across most of our area, this activity has been
fairly weak and free of lightning. While a rumble of thunder or two
will remain possible into this evening due to some elevated
instability that is in place, this general trend is expected to
continue. The exception to this is across the Delmarva, where
greater instability, moisture, and proximity to the warm front will
likely allow for the development of more intense convection. MLCAPE
values across this area have risen into the 1000-1500 J/kg range,
and visible satellite imagery shows that partial clearing has taken
place. An isolated damaging wind gust potential could develop across
this area. Heavy rainfall could lead to some potential for local
flash flooding as well.

Overnight tonight, the warm front will continue to lift northward
across our area. Overall, shower and storm coverage is expected to
diminish. With that said, isolated showers will remain possible
through daybreak. Outside of showers, patchy fog may develop. With
low clouds and warm air advection through the night, lows will
generally be in the low-mid 70s.

A mid-level shortwave axis currently over the Ohio Valley will shift
rapidly eastward tonight, and cross the region towards daybreak
Sunday. This feature should leave some large-scale subsidence in its
wake, suppressing convective development through much of the day on
Sunday. Low clouds should scatter out and at least filtered sunshine
is expected through much of the day on Sunday. With strong afternoon
heating, temperatures will quickly rise into the upper 80s/lower 90s
across most of the area. Dewpoints will be in the low-mid 70s, so
heat indices are expected to be in the upper 90s.

A cold front will approach the area from the northwest by mid-
afternoon. As mentioned previously, the shortwave passage overnight
tonight into early Sunday morning will likely leave some subsidence
in its wake. This is well indicated on forecast soundings across the
area ahead of the front. With that said, the expectation is still
that isolated to widely scattered storms will likely develop across
northeastern PA and portions of northern NJ and track southward
across the area into the evening hours. While storm coverage is not
likely to be particularly high, the environment is still expected to
support severe storms. Forecast soundings indicate MLCAPE of 2000-
3000 J/kg, and deep-layer shear in excess of 30 kt. This should
support organized multicells, and perhaps transient supercells,
capable of producing damaging winds and perhaps a few instances of
severe hail. In addition, deep moisture profiles and PWATs of 1.5-2
inches will support efficient rainfall productions. With the
progressive nature of the cold front, and storm motions generally
off of it, significant flooding concerns don`t appear to be
particularly likely, though localized flash flooding is certainly
possible with any stronger storm.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
Showers and storms should start to taper off by mid evening Sunday.
Latest guidance depicts the cold front near the 95 corridor by 00Z/8
PM EDT, and then southeast of our area by 06Z/2 AM EDT. That being
said, guidance tends to have a fast bias with cold fronts this time
of year, so have gone slightly higher than a blend of models with
PoPs in the 00 - 06Z time frame. Whatever showers and storms linger
will be capable of locally heavy rain, but the gusty wind threat
should wind down after sunset.

In the wake of the cold front, the rest of this period looks much
more pleasant than what we`ve been seeing! Dry air advection will
result in dewpoints in the 50s to lower 60s, and temperatures will
generally top out in the 80s. Large surface high and trailing upper
level ridge will result in dry weather.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
High pressure should still be the dominant feature Wednesday and
should linger for most, if not all of the day on Thursday.

On Thursday however, southwesterly return flow sets up, so expect
temperatures and dew points to start increasing once again. At this
point, it looks like Friday will be the muggiest day, with at least
some chance of seeing heat index values top 100 degrees for almost
all of the region (with the exception of the Poconos and far NW NJ).
Depending on how fast the next cold front comes in, Saturday could
be another muggy day especially for Delmarva and southeastern NJ.

With the approaching cold front, chances for showers and
thunderstorms will increase ahead of the cold front, but with
uncertainty in the timing of the cold front, there is also
uncertainty in the timing of storms.

&&

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

Tonight...There`s a mix of ceilings as I write here at 2330z,
but mainly MVFR. We are expecting a lowering through the
overnight becoming mainly IFR by 05-08Z. A brief period of LIFR
cannot be ruled out for KMIV and KACY towards daybreak. Expect
some fog as well, which could cause visibility restrictions, but
I`m not thinking widespread dense at this time. Winds will be
light and variable. High confidence in overall pattern, but low
confidence in timing and magnitude of the lowest flight
categories.

Sunday...IFR ceilings will quickly lift/scatter out by around
15Z, with BR dissipating as well. Generally VFR conditions are
expected thereafter. Widely scattered showers and storms will
become increasingly likely during the mid-late afternoon hours
from northwest to southeast. Southwest wind 5-10 kt. Visibility
restrictions and strong winds will be possible in any storms.
Moderate confidence.

Outlook...

Sunday night through Thursday...VFR conditions expected.

&&

.MARINE...
Through Sunday...No marine headlines are anticipated. Winds are
expected to remain below 20 kt with seas in the 2-3 ft range.
Scattered showers will be possible today, with scattered showers and
storms possible Sunday afternoon and evening.

Outlook...

Sunday night through Wednesday...winds and seas should stay below
SCA criteria.

Thursday...there is a small chance for wind gusts above 25 kt,
primarily for the Atlantic coastal waters. Otherwise, winds and seas
should stay below SCA criteria.

Rip Currents...

For Sunday, winds will be out of the southwest at 5 to 10 mph
along with breaking waves of 1 to 2 feet and a period of 7 to 8
seconds. As a result, there is a LOW risk for the development
of dangerous and life threatening rip currents at the Jersey
Shore and Delaware Beaches.

For Monday, winds will be out of the north and gradually become
more easterly to even southeast by the evening at 5 to 10 mph. Breaking
waves of 1 to 2 feet and a period of 8 to 9 seconds. As a
result, there is a LOW risk for the development of dangerous and
life threatening rip currents at the Jersey Shore and Delaware
Beaches.

Rip currents occur often in the vicinities of jetties and piers
and the speed of the currents are generally maximized at low
tides.

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

&&

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

&&

$$

SYNOPSIS...Johnson/MPS
NEAR TERM...Cooper
SHORT TERM...Johnson/MPS
LONG TERM...MJL
AVIATION...Cooper/Kruzdlo/Johnson
MARINE...Cooper/Guzzo/Johnson/MPS