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000
FXUS61 KPHI 240223
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1023 PM EDT Tue Apr 23 2024

.SYNOPSIS...
The center of high pressure will continue to build to our south as
low pressure tracks through Ontario and Quebec. This will drag a
cold front will across our region Wednesday. High pressure then
arrives from the Great Lakes Thursday before shifting to our
northeast and east during Friday. A warm front should lift north of
our area late Saturday, then a cold front gradually approaches later
Monday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
High clouds are increasing, but temperatures have fallen fairly
rapidly into the 50s this evening due to both the lack of
clouds and dew points in the low to mid 30s. However, with the
approach of an upper- level trough, clouds and dew points will
both increase through the overnight hours which will slow the
rate of cooling. Overnight lows will be in the upper 40s to low
50s. With the approaching trough, some showers may move into the
region, particularly during the pre- dawn hours Wednesday
morning. However, with the drier air in place, these showers are
expected to remain isolated to scattered so PoPs remain around
20-30%.

The upper-level trough is then forecast to swing across our
region during the day Wednesday. This will drive a cold front
across our area during mainly Wednesday morning, bringing a
break to the showers, particularly across the southern half of
the area. This system looks to have limited moisture with it,
without a tap to Gulf of Mexico moisture, and therefore rainfall
amounts are forecast to be very light. While the main cold
front shifts offshore by early afternoon, a secondary cold front
or trough (dew point front) may arrive by late afternoon. Since
the cold front continues to look faster, more drying is
forecast to be working into the area through the afternoon. This
would tend to decrease the instability, however the model
forecast soundings show some weak instability present in the
afternoon. The overall forcing though may be on the weaker side,
however the model forecast soundings also show lowering
freezing levels and steepening low level lapse rates. If a heavy
shower or thunderstorm were able to develop in the afternoon
ahead of the dew point front, then locally gusty winds and small
hail will be possible. Overall though with the extent of the
drying forecast from about late morning through the afternoon,
the thunder potential looks to be on the low side. PoPs for this
period are around 15-25%. Mild temperatures Wednesday for most
of the area with highs in the upper 60s to low 70s. However, a
strengthening/gusty west to northwest wind will be in place in
the afternoon and evening with gusts of 25-30 mph possible. The
sky will clear especially later in the day as high pressure
begins to build in.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Colder, drier air moves in Wednesday night due to northerly
winds in the wake of the cold front. It looks like the winds may
stay up enough to keep frost from being an issue but it does
look like portions of NW NJ and the southern Poconos will see
lows get down to right around or below freezing so a Freeze
Watch has been issued for our NW NJ zones where the growing
season has started.

A notably colder and dry air mass will be in place Thursday
despite a mainly sunny sky with high temperatures mostly in the
50s. An onshore wind will also keep it even cooler along the
coastal areas. Thursday night may feature more areas of frost
with temperatures dropping into the 30s for much of the area and
lighter winds compared to Wednesday night. This will be
followed by another mainly sunny day for Friday under the
continuing influence of high pressure that will be starting to
shift offshore. This will help cause winds to shift from ENE
early in the day to ESE and then eventually SSE. High
temperatures should be about 5 degrees warmer compared to
Thursday with highs mostly in the low to mid 60s except 50s near
the coast and over the southern Poconos.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Surface high pressure will be over the western Atlantic Friday
night through Saturday as an upper level ridge starts to build
along the east coast. Meanwhile low pressure tracks north and
east into the upper Great Lakes helping pushing a warm front
through PA and upstate NY. This will bring the area a mainly
cloudy day but the chance of showers looks low...only around 15
to 20 percent near the I-95 corridor and 20 to 30 percent over
the Lehigh Valley into the southern Poconos. Highs should be
mainly in the upper 50s to low 60s.

For Saturday night through Sunday, the initial low tracks by
well to to our north over eastern Canada but by later Sunday a
new low will be emerging over the central CONUS. This will help
keep the upper level ridge in place over the east with a
southwest flow at the surface ushering in warmer air. As a
result, expect highs shooting into the mid to upper 70s for most
under variable cloud cover. Right near the coast and over the
Pocono Plateau it will be cooler though with highs mainly in the
upper 60s to low 70s.

By early next week, temperatures have the potential to be even
warmer than Sunday as they may get into the low to mid 80s.
However there will also be an approaching cold front that will
bring chances for some showers and storms beginning as early as
late Monday with better chances for these by Tuesday afternoon
into the early evening.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Rest of Tonight...VFR. A few showers are possible late, but no
reductions in cigs or vsby expected before dawn Wednesday. Winds
south- southwesterly 5-10 kts. High confidence.

Wednesday...Mainly VFR. A brief period of MVFR conditions
possible (15%) with some scattered showers. Winds begin
southwesterly around 10 knots and shift to west then northwest
through the day. Gusts of 20-25 knots by the afternoon. High
confidence on mainly VFR conditions.

Outlook...

Thursday and Friday...VFR.

Saturday and Sunday...VFR overall.

&&

.MARINE...
Latest observations and guidance point towards winds staying
elevated across the Delaware Bay through the overnight period.
With the approach of the frontal boundary, expecting the
pressure gradient to tighten and allow for winds to remain in
Small Craft Advisory criteria as a result. Winds and seas also
picking up a bit earlier across the southern waters, so moved up
the Small Craft Advisory onset time to begin this evening.

Winds across the Delaware Bay will subside around daybreak.
Winds diminish across the coastal waters through the morning,
but remain gusty around 20 kts during the afternoon. Seas will
continue to build, however, peaking around 5-7 feet Wednesday
afternoon.

Outlook...

Wednesday night through Thursday...Small Craft Advisory
conditions Wednesday night with these diminishing Thursday
morning.

Friday through Sunday...The conditions are anticipated to be
below Small Craft Advisory criteria.

&&

.TIDES/COASTAL FLOODING...
A period of southerly flow will occur into Wednesday morning
ahead of a cold front. This is forecast to result in surge
values rising to 1-2 feet above normal along Delaware Bay, the
tidal Delaware River, and Chesapeake Bay. With the full moon
occurring today, astronomical tides will be maximized around
this time as well. This should result in some areas of minor
coastal flooding with the Wednesday morning high tide. As it
stands currently (Tuesday afternoon), sites in the Delaware Bay
and the Chesapeake will touch minor flooding, but stay below the
threshold to issue an Advisory. PETSS guidance remains
relatively bullish on Tolchester Beach getting near Moderate,
with some guidance suggesting they will not even touch minor at
all. If anywhere were to need an advisory, it would be the
Maryland Eastern Shore, but the forecast suggests that isn`t
necessary at the moment.

Coastal flooding is not currently anticipated along the
Atlantic coast, except for potentially Barnegat Bay.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Freeze Watch from late Wednesday night through Thursday
     morning for NJZ001-007-008.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 7 AM EDT Wednesday for ANZ430-431.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ450>455.

&&

$$

SYNOPSIS...Fitzsimmons/Gorse
NEAR TERM...AKL/Fitzsimmons/Gorse/MJL
SHORT TERM...Fitzsimmons
LONG TERM...Fitzsimmons
AVIATION...AKL/Fitzsimmons/Gorse/MJL
MARINE...AKL/Fitzsimmons/Gorse/MJL
TIDES/COASTAL FLOODING...