Perkiomenville Pennsylvania Weather Forecast Discussion

066
FXUS61 KPHI 101949
AFDPHI
Area Forecast Discussion
National Weather Service Mount Holly NJ
349 PM EDT Fri Oct 10 2025
.SYNOPSIS...
High pressure will continue to move further offshore through
Saturday. A coastal storm with significant impacts is expected
to affect the region by Sunday and into early next week.
Improving conditions expected by Tuesday as the storm weakens
and moves out to sea. High pressure will begin building back
into the region during the middle to end of next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
It`ll likely be the best weather (evening/overnight period), of the
next several, as high pressure remains mostly in charge tonight.
We are on the south/southwest side of the high, so onshore flow has
commenced and low level moisture will only continue to increase from
here. Clouds have already arrived for Delmarva and much of NJ attm
and these clouds will remain overnight. The clouds will struggle to
move too far N/W as dry air remains. No rains are expected most
spots tonight. A few models are trying to bring some rains late near
then shore areas, so we`ll go along with some slight chance pops
late tonight. Lows will be milder than the previous night with
mid/upper 40s N/W and low/mid 50s S/E.
The high will be well offshore Saturday. The strengthening onshore
flow will bring increasing clouds to all areas thru the day. Again,
like Friday night, a few models are bringing light rains to many
areas during the day while other are dry. We`ll compromise with only
chance pops for Sat across the region. In addition, slowly
increasing winds will keep temps mostly in the 60s. Winds will start
the day 5 to 10 mph then become mostly 10 to 15 mph late. Gusts will
be 20 mph at times but 20 to 30 mph by late afternoon for the shore
areas.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Things really start to go downhill on Saturday night as a
coastal low approaches from the south. Rain is expected to
continue overspreading the area, with around a 70-90% chance of
rain region-wide. Winds begin to increase, especially over the
water and along the immediate coastline with gusts getting near
40-50 mph by daybreak.
***Significant impacts possible from a strong coastal storm
 Sunday through Monday***
Overview: We continue to closely monitor the anticipated
development of a potentially significant coastal storm near the
North Carolina coast along a stalled frontal boundary beginning
Saturday. This storm is anticipated to strengthen and lift
northward Sunday into early next week. The primary impacts will
be from coastal flooding, beach erosion, dune breaching, strong
to potentially damaging winds, and heavy rain. The heaviest
rainfall and strongest winds are still anticipated to be near
the Atlantic coast.
What has changed: There have been no significant changes to the
forecast or messaging for the storm with this update. There
still remains a fair amount of certainty regarding the details
of the evolution of the coastal storm and its ultimate degree of
impacts. There are still 2 potential solutions, which are most
evident in the differences between the 12Z GFS and NAM model
runs. A stronger storm that tracks closer to the coast will
result in much more severe impacts (similar to the 12Z NAM
solution). A somewhat weaker storm that tracks farther offshore,
(like in the latest GFS runs, as well as previous runs of other
global guidance) will result in less severe, but still
potentially significant impacts to the immediate coast. Guidance
will likely continue to struggle and vary from run to run with
this system until it actually forms a well defined low pressure
center sometime Saturday or Saturday night. All previously
issued watches remain in effect at this time due to the
continued uncertainty in timing, severity, and inland extent of
impacts.
Coastal Storm Forecast Details...
The period Sunday through Monday will be when our area likely
experiences the brunt of the impacts from the coastal storm. If
the current track holds and the coastal storm does end up just
offshore or even making landfall over Delmarva, strong winds are
expected, sustained near 30-40 mph (perhaps near 50 mph along
the immediate coast) with gusts possibly near 60-70 mph along
the coast by Sunday afternoon, Sunday night, and early Monday.
There is potential for these strong winds to continue well into
Monday. Gusts upward of 30-50 mph may extend inland to about the
I-95 corridor and Philadelphia metro area. While there is still
some uncertainty in how long strong winds last, there is at
least high enough confidence that counties bordering the
Atlantic Ocean will either see sustained winds or frequent wind
gusts at/above criteria for a High Wind Warning. As a result,
the High Wind Watch remains in effect for Atlantic coastal NJ
and DE, and their respective counties as periods of 40+ mph
sustained winds and/or frequent gusts near 60 mph are
increasingly likely. Would not be surprised to see a Wind
Advisory for more inland counties, but will wait to issue
anything until confidence on inland extent of the winds is
higher. Long story short, power outages and tree damage are
possible, especially toward the coast.
In addition to the wind, heavy rain is forecast, and a SLIGHT
(2/4) Risk Excessive Rainfall Outlook is in place for the I-95
corridor and points south and east for Sunday through Sunday
night. A widespread 1-3 inches of rain is forecast across our
entire area, with locally higher amounts of 3-5 inches possible,
especially within the SLGT risk area near the coast. While that
sounds like a lot, it is important to keep in mind that this
will be falling over a 36 to 48 hour period. It has been quite
dry as well. Given this, the thinking is that flooding due to
heavy rain alone will be limited to poor drainage and urban
areas. However, that much rainfall could exacerbate impacts near
the coast with Moderate and potentially Major coastal flooding
ongoing. Significant high tides are expected due to strong
northeast winds resulting in water piling up along the coast.
The setup is overall very complex. The surface low will be
developing over the Gulf Stream along a stalled boundary, and
its northward movement will depend on how it interacts with a
surface high over Nova Scotia, an upper level low over the Great
Lakes, and even distant Tropical Storm Jerry. The extent and
severity of impacts in our area will be directly related to the
exact track and evolution of the low pressure center. Stay tuned
to the latest briefing packages and forecast updates as the
forecast continues to evolve and details become more apparent
over the next 24-48 hours.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
The early week coastal storm will be weakening significantly by
Tuesday, but it`s remnant low could still linger in the
vicinity of the coast yielding a chance of showers and somewhat
breezy conditions. The low will eventually weaken and push out
to sea Tuesday into Tuesday night. Thereafter, broad and
relatively weak high pressure will build across the Great Lakes
region. Its cooler airmass will arrive toward the end of the
week, with below normal temperatures and fair weather
anticipated for Thursday and Friday.
&&
.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
thru Sunset... VFR continues with FEW/SCT for the N/W areas and
BKN/OVC for the S/E areas. Bases mostly 040-050 attm. Winds are
mostly E/SE around 10 knots at most. These conditions will continue
with some of the cloudiness spreading NW. High confid.
Tonight... VFR much of the night with an increase in clouds. There
could be some high-end MVFR CIGs arriving towards dawn for the
Delaware Valley and south NJ sites. Light rains may affect coastal
areas, but confid in this not high attm. Light E/SE winds.
Medium/high confid.
Saturday... Differing guidance with MET/NAM showing rains and MVFR
CIGS for many sites during the morning with some improvement after.
GFS remains with a VFR fcst thru the day. We mostly blended the
guidance offering some MVFR CIGS but only mentioned rains where it
seems most probable (KMIV/KACY). East winds 5 to 10 knots.
Outlook...
Saturday Night...MVFR/VFR conditions with light to moderate
rain and lower clouds overspreading the area. Highest chance for
restrictions at the South Jersey terminals. Northeast wind
gusts 25-30 kt at KACY, 20-25 kt at the I-95 terminals and KMIV,
and 15-20 kt at the Lehigh Valley Terminals.
Sunday through Monday...MVFR to IFR conditions expected with
moderate to heavy rain moving through and gusty winds.
Northeast wind gusts up to 50 kt possible at KACY. Gusts out of
the northeast around 25-35 kt expected at the I-95 terminals and
KMIV, with 20-30 kt anticipated within the Lehigh Valley.
Monday Night...Restrictions expected with showers and low
clouds. Wind gusts diminish to around 15-25 kt out of the
north/northeast.
Tuesday...Conditons improve but sub-VFR conditions possible.
Wind gusts could get near 20 kt at times.
Wednesday..VFR with no significant weather.
&&
.MARINE...
Fair weather with sub-SCA for the rest of today and into tonight. No
changes to the near term marine flags Saturday with the SCA flag
expected to go up during the morning for much of the NJ shore as
winds and seas will be increasing thru Sat. There is a small chance
for rains for the marine zones early but no tstms are expected. Rain
chances increase thru the afternoon.
Outlook...
Saturday Night through Monday...A Storm Watch remains in place
through Monday for all marine zones except the upper Delaware
Bay. Northeast winds 35-45 kt and gusts up to 50-55 kt expected
within the Atlantic coastal waters and mouth of Delaware Bay.
Gale Watch in effect for the upper Bay as winds should be
lighter. Dangerous seas upward of 15 to 20 feet expected. Periods
of moderate to heavy rain and sea spray restricting visibility
at times.
Monday night through Wednesday...Conditions will begin to
improve as the storm weakens and begins to move away. However, gale
force winds may linger through Tuesday and elevated seas above 5
feet may linger through Wednesday.
&&
.TIDES/COASTAL FLOODING...
Minor coastal flooding is forecast with Saturday morning`s high
tide, mainly for Atlantic, Cape May, and Cumberland Counties in
NJ and Sussex and Kent Counties in DE. As a result, the Coastal
Flood Advisory now continues through midday Saturday for the
aforementioned areas.
There is an increasing risk of moderate to major coastal
flooding impacts beginning Sunday through Monday as a strong
coastal storm impacts the region. Guidance varies in potential
outcomes of this storm with regard to severity of coastal flood
impacts locally, however we remain very concerned about the
potential for significant impacts from this storm along our
coasts. At this time, the greatest threat of impacts are
anticipated to occur along the Atlantic coasts of New Jersey and
Delaware, and Delaware Bay. A Coastal Flood Watch remains in
effect to highlight this threat for the high tides Sunday
through Monday.
Significant beach erosion and dune breaching are possible along
the entire New Jersey Shore and Delaware beaches due to the very
high surf conditions that are expected. Interests along the
Atlantic coast, Delaware Bay, back bays, and tidal waterways
should remain alert for forecast updates regarding this
potentially significant coastal flood event.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Watch from Sunday afternoon through Monday
     evening for NJZ016.
     Coastal Flood Advisory until 4 PM EDT Saturday for NJZ021>025.
     Coastal Flood Watch from Sunday morning through Monday evening
     for NJZ012>014-020>027.
     High Wind Watch from Sunday morning through late Sunday night
     for NJZ013-014-020-022>027.
DE...Coastal Flood Watch from Sunday afternoon through Monday
     evening for DEZ001.
     Coastal Flood Advisory until 4 PM EDT Saturday for DEZ002>004.
     Coastal Flood Watch from Sunday morning through Monday evening
     for DEZ002>004.
     High Wind Watch from Sunday morning through late Sunday night
     for DEZ003-004.
MD...None.
MARINE...Gale Watch from Saturday evening through Monday evening for
     ANZ430.
     Storm Watch from Saturday evening through Monday evening for
     ANZ431-450>455.
     Small Craft Advisory from 10 AM to 6 PM EDT Saturday for
     ANZ451>455.
&&
$$
SYNOPSIS...OHara/Staarmann
NEAR TERM...OHara
SHORT TERM...AKL/Hoeflich/Staarmann
LONG TERM...AKL/Staarmann
AVIATION...AKL/OHara
MARINE...AKL/OHara
TIDES/COASTAL FLOODING...Staarmann/AKL

NWS PHI Office Area Forecast Discussion