Williamstown New Jersey Weather Forecast Discussion

319
FXUS61 KPHI 080756
AFDPHI
Area Forecast Discussion
National Weather Service Mount Holly NJ
356 AM EDT Wed Oct 8 2025
.SYNOPSIS...
A strong cold front will pass through the region today, then
much cooler high pressure will build into the area through the
end of the week. The high pressure will shift offshore by
Saturday, then a coastal storm will impact the region by Sunday
and into early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Shower activity thus far has been few and far across the
Coastal Plain. However, up in the Lehigh Valley, Poconos, and
northern New Jersey, periods of light to at times moderate rain
has been occurring over the past several hours. As forcing for
ascent continues to overspread the area this morning, shower
activity will increase in coverage over the remainder of the
forecast area by day break as the cold front approaches from the
north and west. Some elevated instability is still present in
forecast soundings, so a few embedded rumbles of thunder remain
possible. Additional rainfall totals should average out to be
around 0.5-1.0" with localized higher amounts possible. Shower
activity will cease by late morning into the early afternoon
from northwest to southeast as the cold front tracks through the
area.
Behind the initial front, skies will scatter out quickly as
drier air filters in from the north with high pressure building
over the northern Great Lakes. Despite afternoon sun, it will
become increasingly breezy as the pressure gradient tightens.
For most areas, northwest winds may gust up to 25-30 mph this
afternoon. As a result, temperatures today will be noticeably
cooler than recent days with highs only topping out in the mid
60s to low 70s.
For tonight, a secondary cold front will push through the
region as skies remain clear with northerly winds diminishing to
around 10-15 mph. It`s behind this secondary front, where a
strong push of cold air will advect into the region. As a
result, low temperatures tonight will bottom out mainly in the
40s, with 50s along the coast, and mid to upper 30s in the
higher terrain. Although, temperatures support frost formation
in some areas, winds should remain elevated enough to preclude
any widespread frost development.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Much cooler and dry conditions expected to the end of the week
following the strong midweek cold front. Widespread frost and
some freezing temperatures is looking increasingly likely
Thursday night for portions of the area.
Troughing from the midweek system will be shifting offshore
into Thursday, then shortwave ridging will briefly pass through
Thursday night through Friday. At the surface, strong high
pressure (~1035 mb) will slide in from the Great Lakes through
this period, centering itself across portions of eastern NY,
northeastern PA, northern NJ, and southern New England by
Thursday night. The high will then begin to shift offshore into
the daytime Friday and Friday night.
Thursday will be the coolest day of the season so far, with
high temperatures struggling to climb above the 60 degree mark
into the afternoon. The higher terrain will likely experience
high temperatures in the mid to upper 50s. 850 mb temperatures
will fall to near 2C to 0C during the daytime, which will
significantly hinder airmass modification despite sunny skies. A
dry 10-15 mph northerly breeze will make it feel cooler.
By Thursday night, the center of the high pressure will reside
across portions of northern NJ and northeastern PA. This is
expected to result in optimal radiational cooling conditions for
those areas and adjacent areas of SE PA and central NJ. This
will support low temperatures in the low to mid 30s for areas NW
of the I-95 urban corridor. Given the clear skies and nearly
calm winds, widespread frost development appears increasingly
likely. Sheltered valleys north of I-78 are forecast to
experience their first freeze of the season. A Freeze Watch was
issued for these areas to highlight this threat.
Interior southern NJ could also see some frost development as
well, but this is somewhat less certain as winds could remain
elevated enough farther south to prevent any significant frost
development. The Pine Barrens have the best chance of frost
development in this area, but at least some patchy frost is
possible in the NJ suburbs too. Interior portions of Delmarva
could drop into the upper 30s, but winds should prevent any
widespread frost formation there. Additional frost/freeze
headlines will likely be needed northwest of I-95 and perhaps
into southern NJ in future updates for Thursday night into
Friday morning.
By Friday, cold advection will have ceased as the high pressure
shifts offshore. This will allow for some airmass modification,
and afternoon high temperatures should easily reach into the
mid 60s under mostly sunny skies. Surface winds will shift
onshore, which could allow for some marine stratus to push in
from the coast later in the day. Friday night will be much more
mild compared to the previous night thanks to onshore winds
advecting in higher dewpoints and increasing cloud cover.
Forecast low temperatures by Saturday morning are in the 40s to
low 50s, though some sheltered areas north of I-78 could dip
into the 30s again with frost development possible. The previous
night`s freeze will likely preclude the need for any frost
hazards though.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
For the long term period over the weekend and into early next
week, the main feature of interest will be the development of a
potentially significant coastal storm near the North Carolina
coast along a stalled frontal boundary. This storm is
anticipated to strengthen and lift northward Sunday into early
next week. Meanwhile, high pressure will remain in place locally
through Saturday with moderating temperatures.
By Saturday, further modification of the airmass is
anticipated, with afternoon highs in the mid 60s to near 70
degrees. Cloud cover will be increasing due to the developing
coastal system to our south, but the daytime period should
remain largely dry.
Guidance continues to vary in the exact evolution of the
coastal storm from Saturday night through early next week, but
we growing increasingly concerned about the potential impacts
locally from this storm. There is still a fairly wide range of
outcomes. A weaker and/or farther south solution with the
surface low would translate to less severe impacts and lower
chances of showers for our region. A stronger and/or farther
north placement of the surface low pressure would translate to
greater and potentially much more severe impacts to our area,
especially along and near the coast. This may include potential
for moderate to major coastal flooding, significant beach
erosion, and strong to damaging winds near the coast and
possibly inland across the coastal plain. Again, to be clear, a
lot of uncertainty with this system, but it bears monitoring
very closely, as significant impacts remain possible.
&&
.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Through 12Z...VFR for now. Conditions should begin to drop to
MVFR by 08Z for KRDG/KABE with remainder of terminals dropping
to MVFR after 10-11Z. Isolated instances of IFR possible, but
largely think MVFR conditions will prevail at this time. Showers
likely with moderate rain possible at times leading to lower
CIGs/VSBYs. South- southwest winds around 10 kt. Moderate
confidence.
Wednesday...Largely MVFR conditions expected to continue with
patchy instances of IFR lingering. Conditions will gradually
improve to VFR from west to east between 14-18Z. South-southwest
winds around 10 kt will become north-northwest around 10-15 kt
with gusts up to 20-25 kt possible in wake of cold front.
Moderate-high confidence overall.
Wednesday night...VFR/SKC. North winds around 5-10 kt. High
confidence.
Outlook...
Thursday through Friday...VFR. No significant weather.
Saturday...Restrictions possible in low clouds. Gusty winds
possible.
Sunday...Restrictions likely in low clouds and showers. Gusty
northeast winds.
&&
.MARINE...
The Small Craft Advisories on the Atlantic coastal waters and
lower Delaware Bay are in effect through tonight. A Small Craft
Advisory has also been issued for the upper Delaware Bay
beginning at 2 PM this afternoon and continuing through tonight.
South-southwest winds of 15-20 kt with gusts around 25 kt are
expected to continue through this morning with seas around 3-5
feet. By this afternoon, winds will transition to northwesterly
around 15- 25 kt with gusts up to 30 kt possible continuing into
tonight in wake of cold frontal passage. Seas build to 4-7 feet
tonight. Showers likely today, before fair weather returns
tonight outside of ongoing SCA conditions.
Outlook...
Thursday through Thursday night...Small Craft Advisory
conditions expected across the Atlantic waters, though with
conditions improving by afternoon and into the night. North to
northeast winds 15-25 kts with gusts up to 30 kts possible. Seas
4-7 feet.
Friday through Friday night...No marine hazards expected. Fair
weather.
Saturday...Winds and seas building, potential to advisory
levels. A chance of showers.
Saturday night through Sunday...A coastal storm will begin to
impact the region. Gale force winds likely developing, with
potential for storm force winds on Sunday. Seas building 12-18
feet. Showers and sea spray likely restricting visibility.
&&
.TIDES/COASTAL FLOODING...
A combination of high astronomical tides (King Tides) and
modest northeast winds is expected to result in areas of minor
coastal flooding with the Thursday morning high tide, and
potentially the Friday morning high tide as well. The areas most
likely to experience impacts will be along the Atlantic coast
from Ocean County and south to coastal Delaware, as well as
Delaware Bay, where surge values will be maximized from the
northeast winds. If the current forecasts hold, advisories will
likely be needed in future updates to highlight this threat.
There is a risk of moderate to potentially major coastal
flooding impacts beginning Sunday and into early next week as a
strong coastal storm impacts the region. Guidance varies in
potential outcomes of this storm with regard to impacts locally,
however we are growing increasingly concerned about the
potentially significant impacts from this storm along our
coasts. At this time, the greatest threat of impacts could be
along the Atlantic coasts of southern New Jersey and Delaware,
and Delaware Bay. People with interests in these areas should
remain alert for future updates regarding this storm.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Freeze Watch from Thursday evening through Friday morning for
     PAZ054-055-061-062.
NJ...Freeze Watch from Thursday evening through Friday morning for
     NJZ001-007.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to 8 AM EDT
     Thursday for ANZ430.
     Small Craft Advisory until 8 AM EDT Thursday for ANZ431.
     Small Craft Advisory until 2 PM EDT Thursday for ANZ450.
     Small Craft Advisory until midnight EDT Thursday night for
     ANZ451>453.
     Small Craft Advisory until 6 AM EDT Friday for ANZ454-455.
&&
$$
SYNOPSIS...Staarmann
NEAR TERM...DeSilva
SHORT TERM...Staarmann
LONG TERM...Staarmann
AVIATION...DeSilva/Staarmann
MARINE...DeSilva/Staarmann
TIDES/COASTAL FLOODING...Staarmann

NWS PHI Office Area Forecast Discussion