696
FXUS61 KPHI 181408
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1008 AM EDT Tue Mar 18 2025

.SYNOPSIS...
High pressure slides across the area today before shifting east
on Wednesday. A cold front will approach the region on
Thursday. As it approaches, weak low pressure will develop along
the front. Both the cold front and low will move through the
region on Thursday Night. High pressure will build across the
area on Saturday. Weak low pressure may move through Saturday
night. Another stronger frontal system is then forecast to
arrive early next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
High pressure is centered over the southern Appalachians this
morning as yesterday`s system continues making slow progress
east off the coast. We remain in the pressure gradient and will
stay there for a few more hours, so winds remain a bit breezy
with wind gusts around 20-25 mph, as temperatures rise into the
upper 30s to low 40s across the region.

Heading into the afternoon, the high builds more strongly over
the area and the system to the east continues making progress
away from us, the gradient should relax and we`ll end up with
lighter winds. Coupled with plenty of sunshine and a bit of
warm advection beginning aloft, and this afternoon should be
considerably more pleasant than yesterday afternoon was, with
highs nudging back into the low 60s for much of the region. A
sea breeze may develop this afternoon as gradient winds become
lighter, which will keep coastal areas in the cooler 50s, while
the Poconos will also stay in the 50s.

Light winds and clear skies tonight as the surface high
pressure axis remains overhead should spell for tranquil night
with radiational cooling, however warm advection aloft may
counter it to an extent. Either way, expect most of the region
to drop back into the 30s, except low 40s in the urban centers
and along the coast.

Wednesday starts mostly sunny, but high clouds will likely
become more noticeable as the day progresses as the next system
to our west begins to approach. The high pressure will split to
an extent with our half being the center which will end up over
the Canadian maritimes. This means the flow will turn
southeasterly, resulting in an increase in marine influence
especially near the coast. Thus, despite warm advection aloft,
highs at the coast will remain just as cool on Wednesday as they
will be today, stuck in the 50s, but well inland, temps may
touch 70.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
An area of low pressure will move through the upper Midwest and
into the Great Lakes region on Wednesday Night, eventually
moving through eastern Canada and dragging a cold front through
our region on Thursday Night. This will result in a period of
wet weather Thursday afternoon into Thursday Night.

Leading up to the cold front, modest southerly flow and warm-
air advection will set up. Airmass won`t be as moist compared to
Sunday Night`s system, but PWATs will eventually get to around
0.9"-1.1", which is at/just above the 90th percentile for mid to
late March. Flow out of the southeast will usher in a marine
layer on Wednesday Night, with patchy fog and drizzle possible
as the night goes on, spreading inland from the coast.
Temperatures Wednesday Night will be in the upper 30s/low to mid
40s.

Thursday likely starts out dry, though with patchy fog/drizzle
possibly hanging around through the morning. Rain moves in for
the afternoon and evening as the front gets closer. Rainfall
amounts will end up around a half inch to an inch for most,
though guidance has trended a bit more progressive with the
front, which could result in lower totals, especially near the
coast. As the front moves through, a secondary area of low
pressure looks to develop, likely directly over our region. As
the low strengthens and pulls away, enough cold air could work
its way in on the backside to bring a few snow flakes, mainly
north of I-78. Not expecting any significant accumulations
though. Temperatures will climb into the mid to upper 60s on
Thursday, and dropping quickly once the front comes through on
Thursday Night. Lows will end up in the low to mid 30s, with 20s
in the Poconos.

Perhaps the largest impact from this system will be the winds
on the backside of the strengthening surface low. High pressure
moving through the Gulf Coast will enhance the gradient,
resulting in gusty winds through the day on Friday. Wind gusts
could approach 50 MPH in the higher elevations with 35-45 MPH
elsewhere. A Wind Advisory may be needed for at least some
areas, but still much too early and will see how things trend
over the next couple days. Strengthening cold- air advection in
the wake of the front will result in below normal temperatures
on Friday, with highs only in the upper 40s/low 50s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Upper level ridging moves in for Friday Night into Saturday,
with high pressure at the surface sliding by to the south. This
brings tranquil weather to kick off the weekend, with winds
weakening quickly as we get into Friday Night. Most of the
deterministic and ensemble guidance has a weak shortwave moving
through later on Saturday, though this system looks moisture
starved. Cannot rule out a few light showers though north and
west of the I-95 corridor late Saturday, but this system looks
like nothing of significance and some guidance has the entire
area staying completely dry. Overall, PoPs are around 20% or so
for northern New Jersey, Lehigh Valley, and Poconos.

Sunday through Sunday Night looks quiet with another area of
ridging moving in before a digging and deepening trough
approaches for the start of next week. This will result in a
surface low lifting into the Great Lakes, and dragging a cold
front through our region. This will be the main system to watch
in the long term as it looks like widespread rain is likely at
some point to start next week. The incoming trough doesn`t look
like it will be in a hurry to depart either, which should bring
unsettled conditions through at least the middle of next week.
Overall, at the very least, it appears some much needed rain is
on horizon.

Temperatures will be near or slightly above normal for late
March through the long term period with highs getting into the
mid to upper 50s, with some 60s mixed in across the southern
half of the region. Lows will generally be in the 30s.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Today...VFR. Winds northwesterly thru this morning with gusts
up to 20-25 kts will become more westerly this afternoon and
diminish to around 10 kts. High confidence.

Tonight...VFR. Westerly winds decrease to less than 10 knots,
potentially becoming light and variable at times. High
confidence.

Wednesday...VFR. Winds becoming southeasterly around 5-10 kts.
High confidence.

Outlook...

Wednesday Night through Thursday morning...VFR to start on
Wednesday Night, but restrictions possible (30-40%) as a marine
layer moves ashore.

Thursday Afternoon through Thursday Night...MVFR/IFR conditions
likely (80-100%) with periods of rain and low clouds moving
through.

Friday...VFR. Northwest wind gusts 30-40 kt expected.

Friday Night through Saturday...VFR. No significant weather.

&&

.MARINE...
Small Craft Advisory now continues for all waters through 12 PM
with winds gusting from the northwest up to 30 kts. Winds on
the bay have remain elevated, resulting in the extension of the
SCA. Wind gusts should drop below 25 kt by around 12 PM across
the bay and by around 2 OM across all coastal waters. However,
seas will remain elevated on the ocean into the late afternoon
and evening, with waves 5-7 feet, so SCA remains up for this
area until 6 PM, by which time both winds and seas should have
dropped below criteria. Sub-SCA conditions then likely continue
through tonight and Wednesday as winds become southeasterly
around 10 kts.

Outlook...

Wednesday Night...Sub-SCA conditions expected, though marine
fog possible (30-40%).

Thursday...SCA conditions expected (80-100%) with seas building
to 4 to 6 feet.

Thursday Night through Friday...Gale conditions likely (60-80%)
with wind gusts 35-40 kt possible.

Friday Night...SCA conditions expected (90-100%) with seas 5 to
6 feet and winds out of the northwest around 25-30 kt.

Saturday...No marine headlines expected.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until noon EDT today for ANZ430-431.
     Small Craft Advisory until 6 PM EDT this evening for
     ANZ450>455.

&&

$$

SYNOPSIS...Hoeflich/Kruzdlo
NEAR TERM...AKL/RCM
SHORT TERM...Hoeflich
LONG TERM...Hoeflich
AVIATION...AKL/Cooper/Hoeflich/RCM
MARINE...AKL/Hoeflich/RCM