351
FXUS61 KPHI 171702
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
102 PM EDT Sun Aug 17 2025

.SYNOPSIS...
A cold front will pass through the region tonight, becoming
stationary over southern Virginia on Monday. High pressure
builds in from the north through the middle to end of next week
as Hurricane Erin passes by well offshore.

&&

.NEAR TERM /THROUGH MONDAY/...
Latest satellite loop showing cumulus field developing over
southeastern PA and interior Delmarva/NJ as surface temperatures
rise into the upper 80s and lower 90s. As a cold front moves
into this airmass later this afternoon and evening, scattered
convection will form and move to the east and southeast roughly
between 22Z and 02Z. Hi-res guidance showing most places will
have little to no rainfall but where storms do form there is the
potential for brief 40 to 50knot wind gusts and a quick
torrential downpour.

Any convection after 02Z will dissipate or move offshore by
late evening with the cold front to follow as it moves through
NW to SE late evening into the overnight. Winds shift from SW
to N/NE around 06Z with a low stratus deck likely setting up.
Lows by Monday morning look to range from around 60 north to
around 70 near the urban corridor, most of Delmarva, and coastal
areas.


Monday looks to be sharply cooler compared to Sunday as northeast
flow and low status persist in the wake of the cold front. The cold
front will stall across southern Virginia and since it will
remain in our proximity, there may be some lingering spotty
showers around. Otherwise the big story will the cooler
temperatures and lower dew points. In fact much of the area
looks to see highs not getting out of the 70s under mostly
cloudy skies.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
A cooler airmass will be moving into the region in the form of a
high pressure system. This will lead to onshore flow and a
continuation of the stark change in overnight lows and day time
highs with lows Monday expected in the low to mid 60s and
daytime highs Tuesday in the low to mid 70s.

A stalled frontal boundary lingering just south of the area
should lead to some isolated shower potential but not expecting
a washout by any means.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The stalled frontal boundary will continue to linger nearby
Tuesday night through Wednesday and as some shortwave energy
moves in from the west, this will bring an increasing chance for
some showers and possibly a few embedded thunderstorms.
Temperatures will remain on the cool side of climo.

The highest impacts in the extended will be from the TC Erin.
The current forecast keeps the storm offshore, however the
prolonged period of onshore flow and high period swells will
likely cause high surf, dangerous rip currents, the potential
for beach erosion, and coastal flooding through the week.

Please refer to the National Hurricane Center for more details
and stay tuned to the local forecast.

The end of the week should feature benign sensible weather
conditions as high pressure should bring fair and dry weather
and seasonable temperatures.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

This afternoon...VFR. Widely scattered showers and
thunderstorms develop after 21Z. Winds southwest around 5-10
kt.

Tonight...Widely scattered showers/storms linger into the
evening with a cold front to follow by the overnight shifting
winds from SW to NW and then NE. Speeds generally remain around
5-10 knots. There also looks to be an MVFR stratus deck that
sets up overnight in the front`s wake.

Monday...A period of MVFR cigs may continue due to low stratus.

Outlook...

Tuesday through Wednesday...Mainly VFR with periods of sub- VFR
conditions possible from showers and thunderstorms.

Thursday and Friday...VFR.

&&

.MARINE...
Southerly winds increase to around 15 to 20 knots but
conditions should stay below Small Craft Advisory levels. Seas
generally 2 to 3 feet.

Late tonight through Monday morning winds veer around to the
northeast in the wake of a cold front and also increase to
around 15 to 25 knots. Seas increase to 5 to 8 feet by late day
Monday. Small Craft Advisory begins at 09z Monday.

Outlook...

Tuesday through Friday...SCA conditions continue due to the
approach of what is currently Hurricane Erin. Elevated winds and
seas develop Tuesday and will last into at least Friday. Seas
5-7 feet Tuesday build as high as 8-14 feet by Thursday.

Rip currents...

For Sunday, southerly wind around 10-15 mph, breaking wave heights
around 1-2 feet, and a dominant easterly swell around 1 foot at 4-5
seconds in length. Typically, these factors would support a low risk
for rip currents. However, given that we have observed longer period
swells (up to 15 seconds in length) that have not been modeled well,
and winds will have at least some onshore component, have opted for
a MODERATE risk for the development of dangerous rip currents for
all beaches.

For Monday, east-northeasterly wind 15-20 mph. Breaking wave heights
generally 2-3 feet. Increasing long period swells propagating from
Hurricane Erin are expected to begin arriving. Given these factors,
have placed a HIGH risk for the development of dangerous rip
currents at all area beaches. A rip current statement will likely be
needed beginning Monday due to this increasing threat.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 6 AM Monday to 6 AM EDT Friday for
     ANZ450>455.

&&

$$

SYNOPSIS...Franklin
NEAR TERM...Fitzsimmons/Franklin
SHORT TERM...MJL
LONG TERM...MJL
AVIATION...Deal/Fitzsimmons/Franklin/MJL
MARINE...Deal/Fitzsimmons/Franklin/MJL