244
FXUS61 KPHI 200627
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
227 AM EDT Wed Aug 20 2025

.SYNOPSIS...
High pressure centered over portions of New England will slowly
drift east. An area of low pressure and associated front will
pass through the region Wednesday into Thursday. Hurricane Erin
will move north, making its closest approach on Thursday, but
remain well offshore. High pressure will build in for much of
the weekend, though another cold front will approach by the
beginning of next week.

&&

.NEAR TERM /THROUGH TODAY/...
High pressure will relax across the area tonight, but the
onshore flow will continue. This will bring more moisture to the
area overnight with some showers especially for E/SE parts of
the area along with increasing and lowering of clouds. Temps
tonight will settle into the low 60s for the N/W counties and
mid/upper 60s elsewhere.

For Wednesday, the increased moisture will remain over the area
while some shortwave energy/weak sfc low will move north of the
area. Hurricane Erin will remain well south of the area. The
system sliding by to the north will pull a warm front into our
area and this will help focus some showers. The highest chances
will be across the N/W areas where the better dynamics will
remain, and an area of convergence may enhance the lift enough
to promote some locally heavier rain. A few thunderstorms cannot
be ruled out mainly in the afternoon. Temps will only top out
in the 70s for north NJ and ern PA while some lower 80s will be
across south NJ and Delmarva. Winds will continue from the East
or Southeast at 10 to 15 mph, strongest at the coast.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
Hurricane Erin makes its closest pass on Thursday, mainly
bringing a plethora of marine and tidal impacts to the region.
While the storm will pass about 350-450 miles south and east of
our area, our region is expected to see gusty winds on the
waters and immediate coast, minor to moderate tidal flooding,
high surf, and life threatening rip currents. Please see the
marine and tides section below for more information.

Wednesday Night starts out with some scattered showers and
isolated thunderstorms lingering over the area as weakening
front moves in from the west. Moisture from Hurricane Erin
advects in with the front in place, as well as an upper level
jet streak moving over the northern third of the area, enhancing
lift north of I-78. Seeing a bit of a signal for a PRE
(predecessor rain event), but thinking the heaviest rates stay
to the north of our area as the timing of the incoming front and
trough don`t quite line up for our area. Thinking it will
mainly just be some scattered showers overnight, but cannot rule
out a few heavier downpours north of I-78, where a MRGL risk
(1/4) risk for excessive rain is in place. Shower activity
should gradually wane through the night. Temperatures drop into
the upper 50s/low 60s north of Philadelphia with mid to upper
60s elsewhere.

Hurricane Erin passes to the south and east on Thursday.
Outside of the immediate coast, it will be a rather benign day
with mostly cloudy and overcast skies, and a northeast breeze in
the upper teens to low twenties. Will be cloudy and cool with
highs only in the low to mid 70s.

Closer to the coast, winds will be stronger, with gusts upward
of 40 MPH possible on the immediate coastline, and 20-30 MPH
within the coastal plain. Also cannot rule out a few light
showers and isolated downpours along the coast, though rainfall
amounts will be negligible. The sea will be quite angry with
very rough surf and life-threatening rip currents, with some
beach erosion possible. The highest tides look to come later
Thursday evening, with widespread minor to moderate flooding
likely. More information can be found in sections below.

For the updated Hurricane Erin forecast, see the National
Hurricane Center`s website at www.nhc.noaa.gov.

Things begin to quiet down on Thursday Night as Hurricane Erin
slowly pulls away. Skies clear out and winds die down overnight.
Should be dry with lows in the mid to upper 50s and low 60s.

Friday actually looks pretty nice outside of rough surf and
high seas. High pressure moves in with mostly sunny skies and
temperatures begin to moderate. Temperatures get into the upper
70s to low 80s as it will be a nice day to close out the week.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Friday night, high pressure will build into the area as
Hurricane Erin moves farther out to sea over the Northern
Atlantic Waters. Winds along the coast will continue to relax,
and skies will be mostly clear. Low temperatures look to be in
the mid 50s for most locations, with low-mid 60s across coastal
regions and the urban corridor. Saturday should be a pleasant
day as well, with high pressure shifting slowly east and
offshore, maintaining influence over sensible weather. Partly to
mostly sunny skies are expected with highs in the low-mid 80s.

Saturday night into Sunday, the upper pattern will begin to
support a period of more unsettled weather, with an upper low
shifting east over portions of Ontario and Quebec, and a
positively tilted trough axis slowly working its way east into
our region. There will be a chance for showers and a few storms
across the region beginning Saturday night. Temperatures looks
to hold fairly steady through Sunday, with highs in the low-mid
80s and lows in the low-mid 60s.

A cold front will eventually work its way through the area,
likely Sunday night into Monday, but while the area is pre-
frontal, shower and storm chances will remain in place. Once the
front clears the area fully Monday night into Tuesday, dry and
pleasant conditions should return.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through 12Z...VFR ceilings lowering MVFR. Some ceilings may
lower to IFR toward daybreak. Some showers possible, with brief
MVFR visibility possible from I-95 and south. East winds 5-10
knots. Moderate confidence overall.

Wednesday...MVFR/IFR ceilings with some showers. A few isolated
afternoon thunderstorms possible. East to east-southeast winds
near 10 knots. Moderate confidence overall.

Outlook...

Wednesday night...MVFR/IFR conditions likely (60-80%) with
scattered showers around and patchy fog.

Thursday...MVFR/IFR ceilings around through most of the day.
Wind gusts 25-35 kt possible at KACY, 20-25 kt at KMIV, and 20
kt elsewhere.

Thursday night through Saturday...VFR. No significant weather.

Sunday...Periods of sub-VFR conditions are possible in some
showers and storms.

&&

.MARINE...
No changes to near term marine headlines. SCA flags fly for
enhanced seas with the first swells associated with `Erin`
arrive across our waters. East to Southeast winds steadily
increase tonight and Wednesday. Fair into the evening for the
northmen waters then rains arrive from South to North tonight.

Outlook...

Wednesday night... A Small Craft Advisory is in place across
all ocean zones as 6-10 foot seas are expected. Wind gusts near
25 kt possible late as winds ramp up quickly with Hurricane Erin
beginning to make its closest approach.

Thursday through Thursday night... A Gale Watch is in place for
all ocean zones and the lower Delaware Bay. Sustained gale
force winds are possible (30-50%), especially over the open
waters. Max wind gusts of 40-45 kt expected. Seas 10 to 15 feet.
Lesser winds are expected on the upper Delaware Bay, where a
Small Craft Advisory is in effect.

Friday...A Small Craft Advisory will be needed on the ocean
once the gales end as seas of 6 to 10 feet are expected, and
winds near 25 kt.

Friday night through Sunday...Winds are expected to have
diminished below 25 kts by Friday night. However, seas will
remain elevated through Sunday, slowly diminishing. Seas as high
as 8 ft Friday night, decreasing slowly to near 5 feet by
Sunday.

Rip Currents...

STAY OUT OF THE WATER!

Through Wednesday, northeast to east-southeast winds 10-20 mph.
A continuation of building seas will lead to breaking waves in
the surf zone increasing into the 5-8 foot range. The conditions
worsen with long period southeasterly swells (15-18 seconds)
associated with Hurricane Erin continuing to arrive. A HIGH risk
for the development of life-threatening rip currents continues
for the Jersey Shore and the Delaware Beaches.

For Thursday, northeast winds 20-30 mph with gusts up to 40
mph. Dangerous surf zone conditions continue as breaking waves
peak at 7-11 feet along with long period southeasterly swells
(15-18 seconds) still associated with Hurricane Erin. A HIGH
risk for the development of life-threatening rip currents
continues for the Jersey Shore and the Delaware Beaches.

A High Surf Advisory is in effect for Wednesday through
Thursday night for the New Jersey and Delaware Atlantic coasts
as waves in the surf zone reach and exceed 8 feet.

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

&&

.TIDES/COASTAL FLOODING...
Prolonged onshore flow will result in periods of tidal flooding
this week. Tidal flooding working up the tidal portion of the
Delaware Bay this evening should be spotty minor.

Water will slowly pile up as onshore flow continues through at
least Thursday. Swells from Hurricane Erin will also enhance the
threat for tidal flooding and push of water onshore, especially
as it gets closer to Wednesday into Thursday. After a round of
mostly sub-advisory minor tidal flooding this evening, more
minor coastal flooding is possible Wednesday.

The potential for a more widespread moderate coastal flood
event as Erin passes Thursday into Friday has increased, so have
issued coastal flood watches for most of the coastal strip at
this time. Uncertainty exists regarding longevity, with some
guidance indicating several cycles could reach moderate, so have
gone a bit long with the timing even though the most confidence
period is late Thursday. Significant coastal flooding is less
likely on the tidal Delaware though advisories may be necessary
here. Even less risk exists along the Chesapeake Bay shoreline.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Watch from Thursday afternoon through late
     Friday night for NJZ021.
     Coastal Flood Watch from Thursday afternoon through Friday
     evening for NJZ013-014-020-022>027.
     High Risk for Rip Currents through Thursday evening for NJZ014-
     024>026.
     High Surf Advisory from 6 AM this morning to 6 AM EDT Friday
     for NJZ014-024>026.
DE...Coastal Flood Watch from Thursday afternoon through late
     Friday night for DEZ002.
     Coastal Flood Watch from Thursday afternoon through Friday
     evening for DEZ003-004.
     High Risk for Rip Currents through Thursday evening for DEZ004.
     High Surf Advisory from 6 AM this morning to 6 AM EDT Friday
     for DEZ004.
MD...None.
MARINE...Small Craft Advisory from 6 AM Thursday to 6 AM EDT Friday for
     ANZ430.
     Gale Watch from Thursday morning through late Thursday night
     for ANZ431-450>455.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ450>455.

&&

$$

SYNOPSIS...Cooper
NEAR TERM...Gorse/OHara/Staarmann
SHORT TERM...Hoeflich
LONG TERM...Cooper
AVIATION...Gorse/Hoeflich/OHara/Staarmann
MARINE...Gorse/Hoeflich/OHara
TIDES/COASTAL FLOODING...