415
FXUS61 KPHI 170945
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
545 AM EDT Sun Aug 17 2025

.SYNOPSIS...
A cold front will pass through the region tonight then becomes
stationary over the Mid- Atlantic into the new week. 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/...
For today, hot and humid weather is on tap once again with a SW
flow ahead of an approaching cold front. Generally expect highs
topping out in the low 90s (mid 80s right near the coast and
over the southern Poconos) with heat indicies generally topping
out in the upper 90s. So it should stay just shy of reaching
Heat Advisory criteria. The day will begin mainly sunny but as
we get into the afternoon and the cold front approaches from the
north and west, there will be some scattered showers and storms
developing...mainly after 19z. ML CAPES by this time look to be
reaching around 1500- 2000 j/kg with deep layer shear around 20
knots. This indicates an environment at least marginally
supportive of severe weather as indicated by the Storm
Prediction Center. Also, with PWATs topping out near 2.25
inches, there will be the threat of heavy rainfall with
localized flash flooding possible with any storms. The timeframe
for these storms looks to be mainly for the latter part of the
afternoon lasting through the first part of the evening as a
cluster or broken line moves through NW to SE. Best chance for
storms around the I-95 corridor looks to be in the 22-01z
timeframe.

Storms start to weaken and move offshore by late evening with the
cold front to follow as it moves through NW to SE late evening into
the overnight. In its wake, winds shift from SW to N/NE 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 should in fact stall just to our south 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 SATURDAY/...
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 /10Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...A scattered to broken deck of clouds around 1800 feet
may continue to bring some periods of MVFR visbys early this
morning at RDG, PHL, and ILG. Otherwise mainly VFR after 12z
through early this afternoon. Scattered showers and
thunderstorms develop after 19z with still some uncertainty
regarding their coverage. However all TAF sites will see a risk
for these storms along with brief restrictions to IFR possible.
Best chances for these storms will be 20-23z at ABE, RDG and
22-01z at the I-95 TAF sites. Winds primarily out of the south-
southwest around 5-10 kt, with south-southeast winds possible
near KMIV/KACY due to sea breeze. Moderate-high confidence
overall.

Tonight...Chances for 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. Overall moderate confidence.

Outlook...

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

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

&&

.MARINE...
Southerly winds increase to around 15 to 20 knots by late day
today 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 9z Monday

Outlook...

Tuesday through Thursday...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 Thursday. 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...Fitzsimmons/Franklin/MJL
NEAR TERM...Fitzsimmons
SHORT TERM...MJL
LONG TERM...MJL
AVIATION...Deal/Fitzsimmons/MJL
MARINE...Deal/Fitzsimmons/MJL