Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 090142
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
942 PM EDT Mon Apr 8 2024

.SYNOPSIS...
High pressure centered to our south will remain there through
Tuesday. A weak system moves through later Tuesday night and
Wednesday with a front draped across our region, then a strong cold
front crosses our area Thursday night into early Friday. High
pressure then builds to our south later Saturday through Sunday,
however a weak cold front may move through later Sunday into Monday.

&&

.NEAR TERM /THROUGH TUESDAY/...
Latest analysis this evening still shows a warm front slowly
advancing northeastward into the region. The front is
accompanied by a fair amount of cloud cover and there have even
been a few spotty sprinkles around over parts of NE PA into NJ
but this is diminishing as of the mid evening hour. Clouds
start to diminish overnight as the front pushes northeastward,
but with the milder air moving from the south, lows overnight
will stay considerably milder than last night...mostly 40s.

Warmer air will surge across most of the region for Tuesday,
along with a decent amount of sunshine, though some clouds will
likely start increasing again ahead of another disturbance in
the afternoon. However, expect dry conditions to prevail through
the day. With the much warmer air mass, highs are expected to
surge well into the 70s across most of the area, though a sea
breeze/bay breeze will keep localities near the Atlantic Coast
and Delaware/Chesapeake bays considerably cooler, with highs
there likely closer to 60.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
While it will be mild overall, it turns unsettled at times as
showers arrive starting later Tuesday night.

A mid level ridge looks to crest over our area early Tuesday night
with surface high pressure anchored off the Carolina coast.
Meanwhile, an upper-level trough sliding across the Midwest and
upper Great Lakes regions will tend to lift to our northwest.
Southern stream energy should be in the form of a closed low that
slides across Texas during Tuesday. The northern stream energy will
have weak low pressure tied to it with a trailing cold front. This
feature shifts eastward however the front looks to stall across our
area Wednesday into Thursday. The location of this weak front will
have some impact on temperatures with the coolest air to its north.

An area of showers arrives later Tuesday night as a burst of warm
air advection teams up with a weak shortwave embedded within the
southwesterly mid level flow. This looks to be on the weak side and
therefore not expecting a lot of rain with this. The chance for
showers continues Wednesday as a front remains in the vicinity and
enough forcing for ascent is present. There does however look to be
dry times. The northern stream and southern streams are forecast to
start merging into a larger and stronger trough later Wednesday.
This supports strengthening surface low pressure in the Tennessee
Valley. Given the continued warm air advection pattern in place and
a deepening low well to our west, southerly flow should support mild
temperatures even during the night as well especially Wednesday
night.

As we go through Thursday, it will be unsettled as an upper-level
trough deepens and slides northeastwards. Given the current forecast
synoptic setup, the parent surface low tracks up across the eastern
Great Lakes into adjacent Canada late Thursday. This will then pull
a strong cold front across our area later Thursday night. Ample
moisture with precipitable water values about 1.50 inches and a
period of strong lift results in showers or even a period of rain,
especially Thursday afternoon and night. Since the air mass is
forecast to be mostly saturated, this would tend to hold down the
instability. This will have implications on the chance, extent and
strength of thunder. The southerly flow ahead of the cold front is
forecast to be robust and therefore plenty of deep-layer shear,
however as of now this may be more of a low CAPE/high shear setup.
This system is forecast to be a strong one and given the forcing for
ascent and wind fields, maintained the mention of possible thunder
for later Thursday and Thursday night. Areas of downpours are
probable given the high moisture content and the potential for more
of a convective contribution, therefore there is at least some flood
risk especially if higher hourly rainfall rates are realized. It is
possible however that this system remains progressive.

It will be mild and more humid ahead the cold front. The
aforementioned robust wind fields ahead of the cold front will
result in a gusty southerly wind, and if enough mixing can occur
within the boundary layer then the winds could gust to 40 mph for
a time.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Summary...Mild overall with a few lingering shower chances.

Synoptic Overview...Northern and southern stream energy completely
merges into a large upper-level trough well to our west to start
Thursday. This through then shifts eastward and may become closed
off in the vicinity of the eastern Great Lakes on Friday. This
entire trough then pivots northeastwards through Saturday before
lifting out into Sunday. There should be a drying trend over the
weekend as the main upper-level trough pivots away from our area,
however some guidance shows another trough starting to approach
later in the weekend into early next week along with a weak cold
front.

For Friday...As a strong upper-level trough slides across the East,
surface low pressure tracks north of the eastern Great Lakes. The
associated strong cold front should be shifting offshore to start
Friday, however a secondary cold front or surface trough may then
move throgh during the day. The deeper moisture should be shifting
to our east and therefore showers are expected to come to an end
during the morning, however some lingering wrap around showers may
occur for a while longer especially closer to the Pocono region. The
much warmer and more humid air mass will be swept offshore with the
cold front, however the main cooling may be delayed until a
secondary cold front or surface trough crosses our area during the
day. This second boundary may be more of a dew point front with cold
air advection occurring. Daytime temperatures should be closer to
average and deeper mixing will result in a gusty wind.

For Saturday and Sunday...The strong upper-level trough should be
gradually pivoting to our northeast Saturday with some lingering
cyclonic flow for a time. A gusty west to northwest wind should be
in place with a tight pressure gradient and better mixing within a
cold air advection regime. At least some model guidance is now
indicating more that another upper-level trough sharpens some as it
drops southeastward out of southeast Canada and slides across the
Northeast. A stronger shortwave within the flow and a weak warm
front approaching may result in a ribbon of lift and therefore some
showers across parts of our area during Sunday (the 12z GFS is
faster with this feature which places its arrival later Saturday).
This is of low confidence, especially as the air mass is forecast to
have dried out following the previous system. Overall, included
mostly slight chance PoPs (20 percent) for now in the gridded
forecast for Sunday.

For Monday...The axis of the aforementioned upper-level trough looks
to be in the process of pivoting across and east of our area. A weak
cold front may also be moving through, however moisture looks
limited as does the forcing. There is low confidence as the strength
and timing of these features can and will probably change.
Temperatures are forecast to be on the mild side.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Tonight...VFR. Light and variable winds with a southwesterly to
southerly trend overall. High confidence.

Tuesday...VFR. Light and variable winds becoming southwest to
south-southeast 5-10 knots. High confidence.

Outlook...

Tuesday night...Ceilings lower to MVFR or IFR along with some
developing showers, especially late. Southeast winds near 5
knots. Moderate confidence.

Wednesday and Thursday...Periods of sub-VFR conditions with showers.
Southeast winds 5-10 knots Wednesday, becoming south-southeast 15-25
knots with gusts 30-35 knots Thursday. Low confidence.

Friday...Sub-VFR conditions with showers especially in the morning,
then conditions should improve. Southwest to west winds 15-20 knots
with gusts up to 30 knots. Low confidence.

Saturday...VFR. West-northwest winds 15-20 knots with gusts to 30
knots. Moderate confidence.

&&

.MARINE...
Winds and seas are forecast to stay below Small Craft Advisory
conditions through Tuesday.

Outlook...

Tuesday night and Wednesday...The conditions are anticipated to be
below Small Craft Advisory criteria (25 knots/5 feet).

Thursday and Friday...Small Craft Advisory conditions. A period of
gale force gusts possible Thursday.

Saturday...Small Craft Advisory conditions probable, however the
conditions should improve at night.

&&

.TIDES/COASTAL FLOODING...
Moderate tidal flooding is now expected along the upper tidal
Delaware River. Minor coastal flooding is still expected with
the next few high tide cycles along the Altantic oceanfront,
Delaware Bay, and lower tidal Delaware River. A Coastal Flood
Warning is now in effect for the upper tidal Delaware River
while Coastal Flood Advisories remain in effect straight into
the overnight period tonight.

With the new moon occurring earlier this afternoon, tonight`s
high tide cycle is expected to be the overall peak of coastal
flooding. However, as we head into Tuesday and Wednesday,
lingering astronomically driven coastal flooding is possible.
This may result in the extension of the current
warning/advisories beyond tonight`s high tide cycle so continue
to check back for updates.

We do not expect any tidal flooding for our Chesapeake Bay
sites.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Warning until 6 AM EDT Tuesday for PAZ106.
     Coastal Flood Advisory until 6 AM EDT Tuesday for PAZ070-071.
NJ...Coastal Flood Advisory until 2 AM EDT Tuesday for NJZ016.
     Coastal Flood Advisory until 1 AM EDT Tuesday for NJZ012>014-
     020>027.
     Coastal Flood Warning until 6 AM EDT Tuesday for NJZ015-019.
     Coastal Flood Advisory until 6 AM EDT Tuesday for NJZ017-018.
DE...Coastal Flood Advisory until 2 AM EDT Tuesday for DEZ001.
     Coastal Flood Advisory until 1 AM EDT Tuesday for DEZ002>004.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Gorse
NEAR TERM...Fitzsimmons/RCM
SHORT TERM...Gorse/Wunderlin
LONG TERM...Gorse
AVIATION...Fitzsimmons/Gorse/RCM
MARINE...Gorse/RCM
TIDES/COASTAL FLOODING...


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