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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 202319
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
719 PM EDT Sat Apr 20 2024

.SYNOPSIS...
High pressure begins building in from the west this afternoon
following the passage of the cold front. The high will be in
place through Tuesday. A cold front passes by on Wednesday. High
pressure then returns and continues through at least Friday.

&&

.NEAR TERM /THROUGH SUNDAY/...
-- Changed Discussion --
With the early evening update, made adjustments to the dewpoints
as dry air advection has been faster than previously expected.
Otherwise, no major changes.

The main concern overnight is the potential for frost. The frost
advisory remains unchanged. Some concern that the dry air will
promote more efficient radiational cooling, and thus could have
more areas with frost. However, it still looks like the winds
staying in the 5 to 10 kt range through the night combined with
increasing high clouds late tonight should help to limit the
cooling. Outside of the advisory area, there may be patchy frost
(especially across the Lehigh Valley), but if so that may end
up being more of the rooftop variety rather than a threat to
vegetation.

On Sunday, dry conditions for most of the region, though as noted by
the previous shift, some guidance continues to show the low off the
southeastern US coast taking a slightly further north track, which
could mean light rain showers edge in to southern Delaware, so have
kept a slight chance of showers there.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
Dry and tranquil weather is expected for the short term period
as a large high pressure will have control over the region. The
high will be initially centered over the Central Plains then
build east through Monday before shifting overhead Monday night.
The high will shift offshore on Tuesday ahead of the next
approaching system.

Skies clear quickly Sunday night as the low from daytime Sunday
moves into the western Atlantic. Skies will then remain clear
into daytime Tuesday. Will have to watch the development for
patchy frost across the Poconos/Lehigh Valley region both
Sunday night and Monday though at this time, development looks
marginal at best, mainly due to winds remaining slightly elevated
overnight around 5-10 mph. Lows each night will generally be in
the 30s to low 40s.

Highs will be in the upper 50s to low 60s on Monday and
increase to the mid-upper 60s on Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
The high pressure that will keep us dry to start the week will
have completely vacated the area by Tuesday night. At the same
time, low pressure will be tracking across the northern Great
Lakes while moving into southern Quebec on Wednesday. An
associated cold front will be trailing southward from this low
which will pass through the area. Areawide showers are expected
with even a few rumbles of thunder possible depending on timing
and available instability. Best chances for this would be north
and west. Once the front clears the area, high pressure will
quickly build in from the west and remain within proximity of
the area to close out the work week. Another low pressure system
may begin to approach the area by next Saturday.

Temperatures through the long term period will run close to average
to a few degrees below-normal. Analogs toward the end of the week
and into next weekend, signal that a significant warm-up may be in
store to close out April.

&&

.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Through Tonight...VFR with mainly clear skies. Winds ease fairly
quickly in the evening, but remaining NW at 10 kt or less. High
confidence.

Sunday...VFR expected. W-NW winds around 10-15 kt. Moderate
confidence.

Outlook...

Sunday night through Tuesday...VFR conditions expected with fair
weather.

Tuesday night into Wednesday...Sub-VFR conditions possible
(40-50%) with rain showers. An isolated thunderstorm is also
possible (15%). Daytime Wednesday is when chances for any
restrictions are highest.

Thursday...VFR conditions expected with fair weather.

&&

.MARINE...
Although winds may gust near 25 kt this evening, winds and seas are
expected to stay below SCA conditions through Sunday.

Outlook...

Sunday night through Tuesday...No marine headlines expected.
Fair weather.

Tuesday night through Wednesday...SCA conditions are possible
(35-45%) with winds gusting around 20-25 knots and seas building
to 3-5 feet. Rain showers expected.

Thursday...Sub-SCA conditions expected with fair weather.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Frost Advisory from 2 AM to 8 AM EDT Sunday for NJZ001-007.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...AKL
NEAR TERM...Johnson
SHORT TERM...AKL/DeSilva
LONG TERM...AKL/DeSilva
AVIATION...AKL/Johnson
MARINE...AKL/Johnson