965
FXUS61 KPHI 200902
AFDPHI

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

.SYNOPSIS...
High pressure centered over portions of New England will
retreat today as a frontal boundary lifts north into the area.
Hurricane Erin will move north, making its closest approach on
Thursday, but will remain offshore and push farther out to sea.
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 TONIGHT/...
Mostly cloudy and showery conditions are expected today into
tonight amid continuing onshore flow and below normal
temperatures. The main hazard of note today is the potential for
isolated instances of heavy rainfall leading to localized
flooding.

Broad diffluence will remain in place aloft with an upper level
jet streak to our northeast into tonight. At the surface, a
slow moving frontal boundary will slowly lift north through
midday, eventually stalling out across northern Delmarva and
east into southern New Jersey.

Scattered showers and some drizzle ongoing north of the frontal
boudnary this morning should generally continue through the
morning. As diurnally driven instability builds into the
afternoon, scattered deep (but not severe) convection should
develop, likely focused in the vicinity of the front. PWats will
be high, but not extreme around 1.7-2.0". Low to mid level flow
is relatively weak, so we should see isolated to scattered
slow-moving tropical downpours developing from around the Philly
metro and south into the coastal plain. This could result in
some isolated areas of locally heavy rainfall and localized
flash flooding, but exactly where this may occur remains
uncertain at the moment. This threat will depend on exactly
where the front stalls out and how much instability develops
(tied to clearing out of low level cloud cover) near and south
of the front. If this ends up closer to the urban corridor, a
more noteable flood threat could materialize, but farther south
and the drier sandy coastal plain soil should be able to take
more rain and result in a lower flood threat. WPC maintains a
Marginal Risk of excessive rainfall across much of the area.

Aside from the convective potential, a mostly cloudy to
overcast day is forecast (breaks of sun more likely toward the
south in the afternoon) with easterly winds around 10 mph. Highs
will range from the upper 60s and 70s near and north of the
Philly metro to the low to mid 80s south of the front in far
southern new Jersey and Delmarva.

For tonight, some isolated to scattered showers could persist
into the evening, but we should see a lull in activity into the
overnight period with low clouds rolling in. Lows will be in the
mid 50s north of I-78, 60s south of there, and near 70 degrees
near the coasts.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Hurricane Erin will bring significant coastal hazards to the
New Jersey Shore and Delaware Beaches beginning Thursday through
Thursday evening. While the center of the storm will pass about
350-450 miles south and east of our area, it will be rapidly
expanding in size with its tropical storm force wind field
reaching just offshore of our coasts. Our region is expected to
see gusty winds, minor to moderate tidal flooding, high surf,
and life threatening rip currents. Please see the marine and
coastal flood sections below for more information.

Hurricane Erin will pass to our south and east, making its
closest approach late Thursday. Outside of the immediate coast,
it will be a rather benign day with mostly cloudy and overcast
skies and breezy northeast winds. Inland areas can expect 10-20
mph winds with gusts up to 30 mph possible. It will also be
relatively cool with highs only in the low to mid 70s.

Closer to the coast, the northeast winds will be stronger.
Sustained winds of 25-35 mph are forecast for the immediate
coastline, with gusts upward of 40-50 mph possible. A Wind
Advisory was issued from 10 AM Thursday to midnight Thursday
night for the Atlantic coastal strip from Ocean County
southward, where sustained winds are most likely to reach
criteria of 31 mph for 2 hours or more. 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
late Thursday evening, with widespread minor to moderate
flooding likely. More information can be found in the associated
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 overnight Thursday Night as
Hurricane Erin slowly pulls away. Skies will clear out with time
and winds will diminish 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 persisting. 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 /09Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through 12Z...Ceilings lowering MVFR and IFR in some spots.
Some showers possible, with brief MVFR visibility possible from
I-95 and south. East winds 5-10 knots. Moderate confidence
overall.

Today...MVFR/IFR ceilings with some scattered showers. A few
isolated afternoon thunderstorms possible, which has been
highlighted by a PROB30 group for TSRA for the I-95 terminals
and south. Any heavier showers or storms cound lead to brief
LIFR conditions. East to east-southeast winds near 10 knots.
Moderate confidence overall.

Tonight...Mainly IFR ceilings expected with some isolated
showers possibly lingering. Winds shifting northeast and
remaining near 10 kts overnight. Moderate confidence overall.

Outlook...

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...
Small Craft Advisory conditions continuing for all Atlantic
coastal waters through tonight with seas 5-8 feet. East to
southeast winds 10-20 kts today, shifting northeast and
increasing to 20-30 kts by dawn Thursday as Hurricane Erin
begins to approach. Some scattered showers may reduce visibility
at times.

Outlook...

Thursday through Thursday night...Winds and seas will build
through Thursday evening as Hurricane Erin makes its closest
pass to our coastal waters. For the Atlantic waters, northeast
winds will increase to 25-35 kts with gusts 40-45 kts possible.
A Tropical Storm Warning was issued where sustained tropical
storm force winds 34 kts or greater are most likely for all
Atlantic zones south of Manasquan Inlet. North of Manasquan
Inland and for lower Delaware Bay, a Gale Warning was issued
where gale force wind gusts of 35-40 kts are forecast, though
sustained winds will remain below 34 kts. For upper Delaware
Bay, a Small Craft Advisory remains in effect for northeast
winds 15-25 kts and gusts up to 30 kts. For the Atlantic waters,
seas are forecast to build to around 12 to 16 feet, even as
high as 10-12 feet nearshore. Scattered showers with locally
stronger wind gusts are possible.

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 kts.

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 until 6 AM EDT Friday for NJZ014-024>026.
     Wind Advisory from 10 AM Thursday to midnight EDT Thursday
     night for NJZ024>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 until 6 AM EDT Friday for DEZ004.
     Wind Advisory from 10 AM Thursday to midnight EDT Thursday
     night for DEZ004.
MD...None.
MARINE...Small Craft Advisory from 6 AM Thursday to 6 AM EDT Friday for
     ANZ430.
     Gale Warning from 6 AM Thursday to midnight EDT Thursday night
     for ANZ431.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ450>455.
     Gale Warning from 6 AM Thursday to 6 AM EDT Friday for ANZ450.
     Tropical Storm Warning for ANZ451>455.
&&

$$

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