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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 021756
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
156 PM EDT Fri Jun 2 2023

.SYNOPSIS...
A strong cold front will slide southward across our region later
tonight into Saturday. High pressure builds in from the north Sunday
into Monday, then another cold front arrives Monday night into
Tuesday. High pressure then builds from the Great Lakes Wednesday to
the Tennessee Valley Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Overall, the near term forecast remains on track. A couple
isolated showers/thunderstorms have initiated across the Lehigh
Valley, southern Poconos and northwest New Jersey. Isolated to
scattered showers and thunderstorms will continue push into New
Jersey and Pennsylvania into this afternoon and evening. It`ll
be a hot day inland with light winds and relatively dry air.

Ridging will remain in place across the region through today then a
positively tilted trough will approach the region overnight. Surface
high pressure remains across northern Quebec. Meanwhile, a broad
area of low pressure will remain across the western Atlantic. Thus,
weak northeast to east flow is expected through tonight.

Temperatures have warmed up across the region early this
afternoon. 850 mb temperatures near 18C will support
temperatures continuing to warm well into the low 90s inland and
even into the mid 70s to near 80 degrees closer to the coast.
This afternoon`s high temperatures inland will be about 10-15
degrees above normal, but will be near normal for locations near
the coast thanks to the marine layer southeast flow pushing
inland. The record highs in jeopardy appear to be Reading (95 in
1925), Allentown (96 in 1925), and Mount Pocono (87 in 1937),
otherwise records are well into the mid-upper 90s. Winds around
around 5-10 mph with varying direction. A northeast direction is
favored, those areas near the coast will have a more southeast
flow.

Mixed layer instability will increase to the 500-1,000 J/kg range
into this afternoon. This combined with no capping and terrain to
force convection is expected to result in some isolated to scattered
showers and thunderstorms developing. The activity should remain
confined mainly to near and northwest of I-95 during the afternoon
and early evening. Given the very deep mixed boundary layer (mixing
as high as 700 mb) and thus dry airmass, DCAPE will be quite high.
This means the showers and storms will be capable of producing gusty
winds thanks to the added evaporation in the downdrafts. A rogue
damaging wind gust is possible, however severe thunderstorms are not
expected at this time. Shear is very low (10 kts or less), so
convection will be pulsy and transient in nature, not organized or
long lived. Small hail cannot be completely ruled out, although a
freezing height near 13kft and the hot surface temperatures should
melt any hail before reaching the ground.

A wildfire in southeast Burlington County, which began Wednesday
afternoon, will continue to result in smokey and hazy conditions
downstream across portions of southern New Jersey and Delmarva. As
of 5 PM Thursday, the fire was 50% contained. Additional spread of
smoke from this fire to areas well south and west from southeast
Burlington County is possible if the fire continues into today.

For tonight, isolated to scattered showers and a few thunderstorms
will linger into the overnight ahead of an approaching backdoor cold
front. The front should also allow for more showers to develop
farther east and south. Little in the way of impacts are expected
overnight with this activity. Winds will become initially light and
variable overnight, although winds will shift northeast and increase
as the front approaches. Expect mostly cloudy conditions overnight
with some low clouds possibly streaming in as well. Lows will be
within a few degrees of 60.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
A strong cold front continues to settle to our south Saturday with
some showers then much cooler air settles in through Sunday.

An upper-level trough is expected to drop southward from eastern
Canada and over the Northeastern U.S. on Saturday, with it
transitioning into a closed low across the Northeast.

As strong cold air advection occurs during Saturday in the wake of
the southward moving cold front, some showers should be sliding
southwestward across our area mainly Saturday morning with a
stronger shortwave nearing the area tied to the based of the upper-
level trough before it closes off. The coverage of showers looks to
be not all that great, and while the region needs the rain this is
not expected to be widespread but at least some spots pick up some
rain. Drier low-level air will advect southward across the area
Saturday, and with a faster push to this much of the area should be
dry in the afternoon. Parts of our far western zones and Delmarva
could hang onto some showers in the afternoon, but overall all areas
should be getting into the drier airmass. A strengthening northeast
wind will occur and this will become rather gusty especially closer
to the coast where peak gusts should be 30-35 mph. This will help
enhance and deepen the marine influence before the much drier air
works southward, therefore cloud cover should hang around through
the morning before breaking up some. Temperatures will be on the
cooler side with temperatures potentially not rising much especially
closer to the coast given the cold air advection and winds off the
cool ocean.

As the upper-level trough transitions into a closed low Saturday
night and Sunday, it is forecast to settle southward and much closer
to our area. This would support a surface low well east of
southeastern New England. Given the colder air aloft associated with
this closed low and shortwave energy rotating around it, a few
showers cannot be ruled out. However, with increased confidence that
the bulk of the forcing along with the deeper moisture will remain
north and northeast of the region, slight chance PoPs (20 percent)
were confined to about the I-80 corridor. Otherwise, a cool air mass
will be in place due to this strong closed low, with temperatures
forecast to be below average, mostly in the 65-75 degree range
during the day then falling back into the 40s to low 50s at
night.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Summary...Temperatures at or below average, with limited chances
for showers.

Synoptic Overview...A closed low is forecast to drift east or
northeastward to just offshore of Nova Scotia Canada early next
week, however a strong piece of energy dives southward and results
in an upper-level trough strengthening across the East. This may
also result in another closed low arriving. The presence of this
trough will result in temperatures being at or below average. Shower
chances look to be limited, however some cannot be ruled out at
times due to the incoming closed low and also a cold front moving
through Monday night into Tuesday. The details however will depend
on the timing of any embedded stronger shortwaves and the cold front.

For Monday and Tuesday...Despite the center of the closed low moving
farther away from our area (just south of coastal Nova Scotia
Canada), an upper-level trough is forecast to remain in place across
the East. This trough may become stronger later Monday and Tuesday
as a closed low drops southward from eastern Canada. The associated
cyclonic flow will maintain a cooler air mass across our area. In
addition, a secondary cold front looks to move through Monday night
into Tuesday. Moisture looks to be limited with this front,
therefore PoPs were kept in the lower chance range (around 30
percent). A breeze should increase Tuesday as a pressure gradient
tightens. Daytime high temperatures are forecast to be at or below
average, with it warmer Monday ahead of the cold front. Overnight
low temperatures drop into the 40s and 50s.

For Wednesday and Thursday...As low pressure moves into the
Canadian Maritimes associated with the center of the closed low,
we will continue to remain under the influence of a large upper-
level trough and therefore cyclonic flow. While the guidance does
differ some with the amplitude and positioning of the upper-level
trough, there is good agreement that a trough is favored. Some
guidance shows the potential passage of a stronger shortwave
Wednesday with upstream convection making a run at parts of our
region. Given the uncertainty, the PoPs are in the 20-30 percent
range. Thursday may be dry as much of the energy is to our north and
northeast, however given the presence of the trough still opted to
include a slight chance (20 percent) for much of the area. Daytime
temperatures each day should be once again at or below average.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Remainder of Today...Mainly VFR expected. Lingering haze and
smoke from the southern New Jersey wildfire may impact MIV/ACY
today, although we are not currently forecasting any visibility
restrictions at this time from this activity. Scattered showers
and thunderstorms have begun to develop, mainly northwest of
the I-95 terminals. Scattered showers and thunderstorms are
expected to continue to develop near and northwest of the I-95
terminals. The chance of a shower impacting a terminal is low,
but if one does, brief MVFR visibility may result along with
brief wind gusts near 40 kts possible. Winds generally 5-10 kts.
Wind direction will tend to be variable at times, although it
should favor a north to northeast direction. The exception will
be at PHL, ILG, MIV, and ACY where winds will be more south to
southeast.

Tonight...Mainly VFR with isolated to scattered showers and
thunderstorms. MVFR to IFR ceilings may develop after 09Z, but
there is low confidence on this. IFR conditions most likely
closer to the coast at KMIV/KACY. Light and variable wind early
will shift northeast and increase to 5-10 kts after 09Z.
Moderate confidence.

Saturday...A period of MVFR/IFR ceilings possible in the
morning with some showers. Ceilings gradually improving to VFR
through the afternoon. Northeast winds 10-15 knots with gusts
20-25 knots. Low confidence.

Outlook...

Saturday night...VFR. Northeast winds diminish somewhat.
Moderate confidence.

Sunday...VFR. North to northeast winds around 10 knots. Moderate
confidence.

Monday...Mainly VFR. A slight chance of showers. North to northwest
winds around 10 knots. Moderate confidence.

Tuesday...Mainly VFR. A chance for showers, mainly in the
afternoon. Northwest winds around 10 knots. Low confidence.
-- End Changed Discussion --

&&

.MARINE...
No marine headlines are anticipated through tonight. Winds will be
from the south to southeast around 10-15 kts today. Winds becoming
lighter tonight and shifting to the northeast. Seas 1-3 feet with a
wind driven easterly swell. Some isolated showers or thunderstorms
are possible overnight.

Outlook...

Saturday...Small Craft Advisory issued as northeast winds increase
from north to south with gusts up to to 30 knots. There is some
potential for a few 35 knot gusts Saturday afternoon and evening.
Seas build to 5-9 feet on the Atlantic coastal waters.

Sunday...Small Craft Advisory conditions should persist into the
morning mainly on our ocean zones, however the winds and seas are
anticipated to be lowering during the day.

Monday and Tuesday...The conditions should be below Small Craft
Advisory criteria.

Rip currents...

Today...There is a LOW risk for the development of dangerous rip
currents for the New Jersey and Delaware beaches. A light and
variable wind in the morning becomes southeast to south around 10
mph in the afternoon. Breaking waves of around 2 feet are expected
with a medium period easterly swell.

Saturday...There is at least a MODERATE risk for the development of
dangerous rip currents for the New Jersey and Delaware beaches.
Northeast winds 15-25 mph with gusts 30-35 mph are expected.
Breaking waves will be 3 to 4 feet with a medium period
east/northeasterly swell.

&&

.TIDES/COASTAL FLOODING...
A gusty northeast wind is expected on Saturday in the wake of a
strong cold front. The onshore flow in combination with the high
astronomical tides associated with the full moon on Saturday will
result in minor coastal flooding along the New Jersey and Delaware
coasts, along the tidal Delaware River and Delaware Bay with the
Saturday night high tide. There is some potential for some spots to
touch moderate flooding, however confidence is low on this scenario.

Minor coastal flooding is possible during the Sunday night high tide
as well, though confidence is much lower on this occurrence.

Coastal flooding is not expected along our portion of the Marylands
Eastern Shore.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 10 AM Saturday to 2 AM EDT Sunday
     for ANZ430-431.
     Small Craft Advisory from 8 AM Saturday to 6 AM EDT Sunday for
     ANZ450>452.
     Small Craft Advisory from 10 AM Saturday to 6 AM EDT Sunday
     for ANZ453>455.

&&

$$
SYNOPSIS...Gorse
NEAR TERM...AKL/Staarmann
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...AKL/Gorse/Staarmann
MARINE...Gorse/Hoeflich/Staarmann
TIDES/COASTAL FLOODING...