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000
FXUS61 KPHI 231950
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
350 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/...
Conditions remain comfortable across the region with temperatures
mainly in the upper 60s and mostly clear skies though some cirrus
clouds are beginning to move into the region. With only a few high
clouds around at sunset, temperatures will fall fairly rapidly into
the mid 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 /20Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Through today...VFR. Southerly winds around 10 kts. Gusts of 15-20
kts possible this afternoon. High confidence.

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...
Winds are beginning to reach Small Craft Advisory levels on the
Delaware Bay, as well as the northern half of the New Jersey coastal
waters. Therefore, a Small Craft Advisory remains in place for these
areas. Tonight, the gusts on the bay diminish, but on the oceans
they should increase, so SCA`s expand to all ocean zones after
midnight. Seas will also build, reaching low-end criteria by early
Wednesday morning. During the day Wednesday, seas continue to build,
peaking around 5-7 feet. Gusts will begin to diminish but likely
remain elevated around 20 knots.

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.

&&

.FIRE WEATHER...
Though there will be some moisture advection with an
approaching system, the region will remain fairly dry today. Min
RH values across the region will be in the 25-35% range, with
southerly wind gusts in 15-25 mph range. As was done for Monday,
a Special Weather Statement for increased fire danger has been
issued for today.

&&

.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 night high tide, although
the extent and exact areas that may experience the most impact
remains unclear at this time.

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 8 PM EDT this evening for ANZ430-
     431.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ450-451.
     Small Craft Advisory from midnight tonight to 6 AM EDT
     Thursday for ANZ452>455.

&&

$$

SYNOPSIS...Fitzsimmons/Gorse
NEAR TERM...AKL/Fitzsimmons/Gorse
SHORT TERM...Fitzsimmons
LONG TERM...Fitzsimmons
AVIATION...AKL/Fitzsimmons/Gorse
MARINE...AKL/Fitzsimmons/Gorse
FIRE WEATHER...WFO PHI
TIDES/COASTAL FLOODING...WFO PHI