930
FXUS61 KPHI 201029
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
629 AM EDT Sun Apr 20 2025

.SYNOPSIS...
In the wake of the cold front Saturday Night, high pressure
builds over the region through Monday. Another weak cold front
is expected Monday night into Tuesday. High pressure will be in
control through Thursday. Another low pressure system may
arrive Friday into Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...

Our cold front has been moving slower through the area which has
played a role in temperatures. The temperature forecast has been
updated to align better with surface observations. The cold
front is still expected to move through today and settle south
of the area.

Previous discussion:


The cold front settles to the south of our area today and winds
will be out of the northwest at around 5-10 mph with gusts at
times to 20 mph. Today will also be cooler than Saturday as
highs reach the mid 60s to low 70s. A high pressure system will
be in control through tonight. This will lead to a mostly to
partly sunny day.

High pressure starts to slide offshore Sunday night, but we
continue to stay dry with a partly to mostly cloudy sky.
Overnight lows will generally be in the mid 40s to low 50s.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Relatively cool and cloudy conditions are expected to prevail
on Monday thanks to the marine layer, while a weak cold front
Monday night into Tuesday will bring a quick chance for light
rain.

For Monday, onshore flow and the marine layer will keep the
region relatively cool despite the fact that our region will
technically be in the warm sector of the next approaching low
pressure system. Highs are generally expected to be in the 50s
and 60s across the region.

Monday night into Tuesday morning, the cold front associated
with the previously mentioned low pressure system will approach
and sweep through the region. As mentioned by the previous
shift, the time of day, presence of the marine layer, and the
lack of stronger forcing will mean just a quick shot of light
rain for most of the area. The possible exception to this is
portions of Central Delmarva. The front is expected to slow and
eventually stall south of our region. Depending on how close
this occurs to central Delmarva, chances for light rain could
linger through Tuesday night.

The shift to off shore flow in the wake of the cold front will
mean that Tuesday will actually be warmer than Monday, with
highs mostly in the 70s, but could get close to 80 for some
areas.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
High pressure will be the dominant feature to start this
period, leading to mostly tranquil conditions through Thursday.
The next low pressure system is expected to lift into the Great
Lakes region, and bring our area another chance for rain at the
end of the week.

For Wednesday and Thursday, highs will be mostly in the 70s
across the region. However, there is a chance that onshore flow
could develop once again on Thursday. If that were to happen,
temperatures, especially over the coastal plain may be cooler
than the current forecast.

The late week system is another case of the main surface low
staying well northwest of our region, but the associated cold
front progressing through our region. Still some question on the
timing, but much of the latest guidance depicts the front
clearing well south of our region before stalling, so this may
once again end up being more of a quick shot of rain.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Sunday...VFR conditions expected with just some high clouds across
the area. West/northwest winds 10-15 kt, gusting to 20 kt through
about 18z-19z or so then diminishing. Some guidance wants to develop
a sea-breeze getting to KACY, but modest northwest flow would
prevent one from moving far inland. Moderate confidence.

Sunday Night...VFR. Flow turns onshore with east/northeast winds
around 5 kt. With onshore flow developing, cannot rule out a marine
layer working inland, but confidence is low on if it will develop
and if there will be restrictions if it comes to fruition.

Outlook...

Monday and Monday night...Periods of MVFR or even IFR ceilings are
possible with persistent E and SE flow.

Tuesday...Quick improvement to VFR conditions likely. NW wind gusts
up to 25 kt.

Wednesday and Thursday...VFR conditions likely.

&&

.MARINE...

Wave heights have continued to decrease, so the Small Craft
Advisory was allowed to be cancelled. Winds and seas are
expected to stay below Small Craft Advisory criteria through
Sunday night.

Outlook...

Monday...winds and seas should stay below SCA criteria.

Monday night into Tuesday...SCA conditions are possible, primarily
on the Atlantic Coastal Waters.

Tuesday night through Thursday...winds and seas should stay below
SCA criteria.

&&

.FIRE WEATHER...
On Sunday, Min RH values will be around 20-30% across the
region. Northwest winds gusting up to 25 mph especially in East
Central PA and Northern NJ. Unsure of the current state of the
fuels after last evening`s showers. Will coordinate further with
state partners in PA and NJ later this morning.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Johnson/OHara/RCM
NEAR TERM...Guzzo
SHORT TERM...Johnson
LONG TERM...Johnson
AVIATION...Guzzo/Johnson
MARINE...Guzzo/Johnson
FIRE WEATHER...