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000
FXUS61 KPHI 201735
AFDPHI

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

.SYNOPSIS...
A cold front moves offshore this morning. High pressure builds in
from the west this afternoon which will be in place through Tuesday.
A cold front passes by Tuesday night and Wednesday. High pressure
then returns and continues through Friday.

&&

.NEAR TERM /THROUGH SUNDAY/...
The cold front has crossed off shore and south of our region.
though there is a secondary cold front that is forecast to
sweep through later this afternoon into this evening which may
bring another surge of cold air advection.

Have seen some clearing, though stratocumulus has developed in
the wake of the front, especially for areas near and east of the
Delaware Valley. Consequently, adjusted cloud cover up for the
next few hours. That being said these clouds should dissipate
closer to evening as cooler air ushers in to the region.

With a secondary push of cooler and drier air coming in for
tonight, dewpoints will continue to drop through the 20s, lowest
in areas northwest of the urban corridor. There will be some
high clouds possible, but overall skies will be fairly clear,
and with high pressure building in from the Ohio Valley, we may
see decoupling, easing winds and some rather chilly temperatures
into the 30s by Sunday morning. Made no changes to the Frost
Advisory for Sussex and Warren counties. Will keep watching
trends if it needs to be expanded, but forecast temperatures in
other areas are very marginal for frost, and high clouds may
come in toward morning that would limit frost formation. Either
way, would not rule out patchy frost across the Lehigh Valley,
though 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.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Mostly dry and tranquil weather is expected for the short term
period. The cold front that passes through on Saturday will be
stalled out along the Southeast coast. A weak surface low is
forecast to develop along this boundary and skirt off the Carolina
coast late Sunday. At the same time, large high pressure will be
centered over the Central Plains which will build east through
Monday before shifting overhead Monday night.

Skies clear quickly Sunday night as the low moves into the
western Atlantic. Skies will then remain clear through Monday
night. Will have to watch the development for patchy frost
across the Poconos/Lehigh Valley region both nights.

Highs will be in 50s to around 60 on Sunday, followed by the upper
50s to mid 60s on Monday. Lows generally in the 30s to low 40s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
High pressure begins to shift offshore on Tuesday before completely
vacating 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.

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

Through 00Z...VFR conditions expected. West/northwest winds 10
to 15 kt. May see a few hours period of gusts to 25 kt between
20 and 00Z. High confidence.

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 with mostly clear skies. W-NW
winds on Sunday night into Monday, becoming SE-S winds on Monday
night into Tuesday. High confidence.

Tuesday night into Wednesday...Sub-VFR conditions possible with rain
showers. S winds becoming NW following a cold frontal passage. Low
confidence.

&&

.MARINE...
While some of the buoys offshore still show some near 5 ft seas,
overall conditions are below SCA criteria. Fog has diminished as
well. West to southwest winds will pick up around 10-15 kt
heading into this afternoon. A secondary cold front will swing
winds around to the NNW tonight, with gusts over 20 kt, but
probably not enough for another advisory.


Outlook...

Sunday through Tuesday...No marine headlines expected. Fair weather.
Winds up to 15 kt and seas around 2-3 feet.

Tuesday night through Wednesday...SCA conditions are possible. Rain
showers expected. Winds up to 20-23 kt with seas around 3-4
feet.

&&

.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...MPS
NEAR TERM...Dodd/Johnson
SHORT TERM...DeSilva
LONG TERM...DeSilva
AVIATION...Dodd/DeSilva/Johnson
MARINE...Dodd/DeSilva