Bensalem, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

998
FXUS61 KPHI 031731
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1231 PM EST Tue Dec 3 2024

.SYNOPSIS...
Cold and dry high pressure will remain in place to our southwest
today. Strengthening low pressure will then track to our north
later tonight into Thursday, pushing a strong cold front across
our area early Thursday along with windy conditions. Cold and
dry high pressure will build into the Ohio Valley Friday through
Saturday before weakening into our area through Sunday. A weak
low pressure system and front may impact the region late
Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As we head into the day today, high pressure continues to slowly
approach from the west while in the upper levels the area remains
under the influence of a broad long wave trough. Expect some
shortwave energy to rotate around this trough through the area
as we get into the afternoon hours. The upshot of all this is
that it`s looking to be another chilly and breezy day with
variable cloud cover. The most cloud cover should continue to be
in our northern and western zones through the Lehigh Valley
into the southern Poconos and NW NJ where there could even be
some scattered flurries or snow showers in the afternoon as the
trough swings through. Areas near the coast should see the most
in the way of sunshine. Winds will continue to be a little
breezy at around 10 mph with some gusts of 20 to 25 mph possible
in the afternoon. Expect highs mainly in the upper 30s to low
40s except low to mid 30s over the southern Poconos and NW NJ.

For tonight, it will be mainly clear and cold as surface
ridging builds in right over the area. Expect lows by Wednesday
morning mainly in the low to mid 20s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A strong storm system will impact the region Wednesday night
through Thursday night, bringing potential for rain and snow
showers, strong winds, and continued below normal temperatures.

Synoptic Overview...Shortwave ridging will pass quickly across
the region on Wednesday as a deep positively tilted trough
approaches the Great Lakes. The trough axis will dive quickly
southeastward across the Mid Atlantic early Thursday while
becoming negatively tilted as it shifts offshore. Height falls
quickly spread across the area Wednesday night into Thursday
morning. At the surface, a strengthening low pressure system
will pass just north of the Great Lakes Wednesday reaching the
Canadian Maritimes late Thursday. A strengthening pressure
gradient will result beginning Wednesday, remaining in place
through Thursday night. A strong cold front will sweep through
the area Thursday morning, likely offshore by the afternoon. The
frontal passage will yield very strong cold advection in its
wake, with 850 mb temperatures upstream around -10C to -15C.
Post frontal surface pressure rises will be near 1 mb/hour.
This is not a clipper system, to be sure.

Details:

Wednesday...Wednesday will feature fair weather, but with
increasing cloud cover and a strengthening south to southwest
breeze as the surface low strengthens well to our northwest. The
airmass advecting is really just a modified arctic airmass that
has been in place across the Southeast. So while technically a
warm advection regime, the air will not be particularly warm or
moist. Nevertheless, high temperatures will see a boost of a
couple degrees across the board into the upper 30s to mid 40s.

Wednesday night...As stronger forcing for ascent arrives
overnight, precipitation should develop within the region, with
the greatest chances (60-70%) residing mainly north of the
Philly metro. Within the Philly metro and south, less forcing
should result in more spotty or showery nature to the
precipitation. Areas along and north of the I-78 corridor will
likely see mostly snow with this activity, with a rain/snow mix
farther south and mainly rain near the coast. QPF is light,
largely less than 0.10". Any snowfall accumulation outside of
the Poconos and higher elevations of northwest New Jersey will
remain less than 1". The higher elevations and southern Poconos
could see about an inch or two of snow for Wednesday night. A
southwest breeze will be strengthening overnight as the cold
front approaches, and especially toward daybreak to around
15-20 mph, with gusts near 25-30 mph possible. The winds, mixed
boundary layer, WAA, and cloud cover will keep temperatures
relatively mild, perhaps even rising a few degrees overnight.
Forecast low temperatures are mainly in the 30s.

Thursday through Thursday night...The strong cold front will
quickly approach and begin passing through the forecast area
just after daybreak Thursday, and should be offshore by around
noon or so. If moisture is sufficient, some snow showers or
snow squalls could develop along or just ahead of the frontal
boundary following the diminishing overnight precipitation. The
limiting factor for any impacts from this activity will be
surface temperatures, as most areas south of I-78 will be above
freezing with above freezing roadway temperatures. Nevertheless,
a quick dusting a snowfall could result in grassy and elevated
surfaces as far south as the coastal plain. An additional inch
or two of snowfall is forecast for the southern Poconos, and a
Winter Weather Advisory may need to be considered in a future
update for this area given event totals of 1-3". Temperatures
will likely reach their daytime maximum in the mid 30s to low
40s in the morning, then gradually fall into the afternoon.

Beyond the shower potential with the front, the main story will
the the windy conditions expected in its wake. I am hard
pressed to find any deterministic guidance showing anything less
than widespread 35-45 kts of wind within the 925 to 850 mb
layers during the post-frontal regime. BUFKIT profiles indicate
we`ll be mixing up to around the 800-850 mb layers post-frontal,
so I think it`s reasonable to assume those winds speeds should
translate to peak gusts at the surface given extremely strong
cold advection, shortwave vort max pivoting through aloft with
FROPA, and surface pressure rises around 1 mb/hour. Long story
short, we are growing increasingly confident that our area will
experience widespread 40-50 mph wind gusts for much of the
daytime period Thursday. Expect westerly sustained winds near
20-30 mph. A Wind Advisory for Thursday appears more probable
as of this update.

With cold advection and a strong pressure gradient persisting
Thursday night, strong winds will likely persist much of the
night, though gradually lessening with time. Low temperatures in
the 20s will yield wind chills in the low to mid 10s for much of
the area, by far the lowest wind chills we have experienced so
far this season.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
High pressure builds to our west on Friday with mostly
clear/sunny skies. Breezy conditions continue with a northwest
wind gusting to 25-30 mph. Highs Friday afternoon will be in the
30s with overnight lows in the teens and 20s.

For Saturday and Sunday...While the upper-level trough is
forecast to not be as strong over the weekend, another shortwave
may sharpen the trough some Saturday. Temperatures will remain
below normal, however with some less amplification of the
trough the temperatures should start to rebound at least a
little Sunday. In addition, the aforementioned shortwave within
the main trough could support some forcing for some isolated
showers and increased cloud cover. However, this solution is
appearing less likely, and most guidance shows surface ridging
extending into the region during this period. PoPs were reduced
outside of the Poconos. The winds will be much less as the
pressure gradient is weak with surface high pressure starting to
extend toward or into our area from the southwest.

Monday...Long-term guidance suggests Monday could be unsettled
with an amplified trough shifting across the central US. That
said, guidance remains in large disagreement with the evolution
of the system. That said, it does look like the system will be a
bit warmer with less chances for any wintry precip. We have
carried chance PoPs for the area during this period.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

This Afternoon...VFR with occasional SCT/BKN ceilings around
5000-6000 feet. W-NW winds around 8-13 kt with locally higher
gusts near 18-20 kt possible. High confidence.

Tonight...VFR. West winds around 5 kt. High confidence.

Outlook...

Wednesday...VFR with increasing coverage and lowering of
ceilings. South to southwest winds 10-15 knots.

Wednesday night...Sub-VFR conditions likely developing along
with rain or snow showers, especially at RDG/ABE. Southwest
winds 10-15 kts with gusts of 20-25 kts possible. LLWS
possible.

Thursday through Thursday Night...MVFR to IFR conditions early,
with improvement to VFR conditions by midday. Windy. West winds
increasing to around 20-25 kts with gusts 35-40 kts. Winds
lessen Thursday night.

Friday...VFR. West-northwest winds near 15 kts with gusts 20-30
kts, diminishing in the evening.

Saturday...Mainly VFR with moments of sub-VFR conditions
possible, primarily north. SW winds 10-15 kts with gusts to 20
kts.

&&

.MARINE...
No marine headlines are in effect through tonight. Northwest
winds around 12-17 kt with gusts up to 23 kt and seas of 2-4
feet. Otherwise, fair weather.

Outlook...

Wednesday...Small Craft Advisory conditions developing quickly
by late afternoon.

Wednesday night through Thursday night...Gale Watch remains in
effect. Gale force winds likely developing Wednesday night,
peaking Thursday, then gradually diminishing Thursday night.
Wind gusts 35 to 45 kts possible. The strong offshore winds
could result in abnormally low water during the Thursday late
afternoon to evening low tide, which could make navigation
difficult in shallow waters.

Friday...Small Craft Advisory conditions abating into Friday
night.

Saturday...The conditions are anticipated to be mostly below
Small Craft Advisory criteria.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Watch from Wednesday evening through late Thursday night
     for ANZ430-431-450>455.

&&

$$

SYNOPSIS...MJL/Staarmann
NEAR TERM...DeSilva/Fitzsimmons
SHORT TERM...Staarmann
LONG TERM...MJL/Staarmann
AVIATION...DeSilva/Fitzsimmons/MJL/Staarmann
MARINE...DeSilva/Fitzsimmons/MJL/Staarmann