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000
FXUS61 KPHI 122347
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
747 PM EDT Fri Apr 12 2024

.SYNOPSIS...
A secondary cold front will cross the region tonight as an area
of low pressure will move into eastern Canada on Saturday.
Several weak surface troughs will move across the Mid-Atlantic
region into Saturday. High pressure will build across the
southeast states over the weekend, before an area of low
pressure moves out of the Great Lakes and into the northeast
states Sunday into Sunday night, bringing a cold front to the
Mid-Atlantic region. High pressure briefly builds across the
region Tuesday, before a series of frontal boundaries and low
pressure systems affect the east coast Wednesday through Friday.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 730pm...Strong ~980mb surface low is now positioned over
southwest Quebec with the main cold front tracking across
portions of New England. A few scattered showers have developed
in association with the parent upper level low spinning to our
north and west, so have kept the mention of showers across much
of the area for the next several hours.

Otherwise, the secondary cold front is now moving across Ohio
and is about to enter western Pennsylvania. This boundary will
cross the region later tonight accompanied by another shortwave
rounding the bottom side of the closed low in southern Canada.
Thus, while precip coverage is scattered for now, more
widespread showers particularly from I-95 north and west and
especially across the Poconos later tonight into early Saturday
is expected. Temps likely even cool enough for a change to snow
in the higher elevations of the Poconos, but little if any
accumulation is expected.

As high pressure starts to build in and the upper low pushes
off the northeast Saturday into Saturday night, precip will
dwindle and then clouds will gradually break. Winds will remain
elevated through Saturday evening, with continual gusts of
20-25 mph early this evening, before gusts increase again
behind the secondary front and with increased mixing on
Saturday. We may be close to wind advisories across much of the
area, with currently forecast gusts around 40 mph being just shy
of criteria (46 mph/40 kts). For now, will punt that decision
to the mid-shift as confidence is low. As high pressure builds
to our south Saturday night and the gradient relaxes, should see
winds drop off below 10 mph overnight with clearing skies.
Temps will drop into the 40s tonight and rising only into the
50s on Saturday before dropping into the 40s again Saturday
night. The Poconos will be about 10 degrees colder than these
numbers, however.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Sunday will begin dry as slight surface ridging moves offshore,
before a warm front clips the area later in the day, followed
by a cold front overnight. Precipitation chances increase later
in the day and into the night Sunday. Guidance is indicating
some instability across the area later in the day and into the
night, so there will be a chance for a few thunderstorms. There
is a fair amount of shear due to a belt of 50-60 knot 700-500 mb
winds, so if there are any thunderstorms, so locally strong
winds could develop, mainly over northeast Pennsylvania and
northern New Jersey. Shower and thunderstorm activity will
diminish during the night.

The cold front will push to our south by Monday, before weak
high pressure approaches from the northwest overnight. Dry
weather is expected to be in place for the start of the work
week into Monday night.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
On Tuesday, the weak high pressure will briefly build across
the Mid Atlantic region, keeping dry weather through the day.
However, this will only be temporary as shower chances will
increase overnight as a warm front approaches from the south.

The warm front will likely linger across the forecast area
through the day Wednesday and into Wednesday night, keeping
elevated chances for showers, and even a few thunderstorms. A
cold front is forecast to move across the area Thursday into
Thursday evening, keeping chances of showers in the forecast
through Thursday night. Yet another cold front could bring
another round of showers during the day Friday into Friday
evening.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Tonight...VFR for most terminals before ceilings are expected
to lower to MVFR by 06-07Z at KRDG/KABE. Ceilings at
KTTN/KPNE/KPHL may have some scattered low clouds, but generally
expect VFR tonight. KILG/KMIV/KACY should remain VFR. Isolated
to scattered showers are expected at all terminals tonight. SW-W
winds of 10-20 kt with gusts up to 25-30 kt possible after
frontal passage late. Moderate confidence overall, but lower
confidence with regard to ceilings lowering.

Saturday...MVFR to start for all terminals, with the exception
of KILG/KMIV/KACY which should be VFR. A few lingering showers
are possible north and west, but ceilings should gradually
improve to VFR between 16-18Z. W-NW winds of 20-25 kt with gusts
up to 35-40 kt possible in the afternoon. Moderate confidence.

Saturday night...VFR with mostly clear skies. W-NW winds of 10-20
kt early diminishing to 5-10 kt. High confidence.

Outlook...

Sunday...VFR conditions expected most of the day, before Sub-
VFR conditions possibly develop for northern areas late in the
day as showers/possible thunderstorms approach the area.
Southwest winds 10- 20 knots, with gusts 20-30 knots. Moderate
confidence.

Sunday night...Sub-VFR conditions could develop across the area
as showers/possible thunderstorms move across the area. Winds
become west and northwest 5-10 knots overnight behind a cold
front. Moderate confidence.

Monday-Monday night...VFR conditions expected. Northwest winds
5-10 knots with gusts 15-20 knots during the day.

Tuesday-Tuesday night...VFR conditions exected. Northwest winds
5-10 knots early, become variable during the day, then south to
southeast during the evening and overnight. Moderate
confidence.

Wednesday...Sub-VFR conditions likely with showers. Southeast
winds 5-10 knots. Low confidence.

&&

.MARINE...
Small Craft Advisory conditions presently with westerly winds
gusting up to 25 kts and waves of 6 to 10 feet. Seas diminish
overnight to 5 to 8 ft with winds diminishing a bit in the
evening before increasing behind a secondary cold front late
tonight. Gales then expected to redevelop across most waters on
Saturday behind said front with W to NW gusts up to 35 kts for a
fair chunk of the day. Winds wind down back to SCA levels by
Saturday evening and then sub-SCA overnight, with waves dropping
to 2-4 ft by late night as well.

Outlook...

Sunday-Sunday night...Small Craft Advisory conditions expected.

Monday-Tuesday night...Conditions expected to fall below and
remain below advisory levels into early next week.

Wednesday...Conditions may return close to advisory levels on
Wednesday.

&&

.TIDES/COASTAL FLOODING...
The coastal flood threat continues to diminish compared to
Friday morning, but unfortunately due to a lingering surge of
water trapped in some of the back bays as well as up the
Delaware River, with continued runoff from the recent rainfall,
some more localized areas of minor flooding will continue
tonight, and even with Saturday morning`s high tide along the
lower Delaware River.

The back bay locations where coastal flooding remains a problem
are particularly around northern Barnegat Bay in Ocean County,
as well as Little Assawoman Bay in Sussex County, DE. Extended
the Coastal Flood Advisory until Midnight for the former, as
water levels still have a ways to go before they drop below
minor flood stage, as within the back bays water struggles to
drain out to the ocean. Further tidal flooding is NOT expected
oceanside.

While the this morning`s crest along the lower Delaware River
did not quite reach expectations, moderate flooding levels were
still achieved. With the current tidal anomaly running between
1.6 and 1.9 feet, this evening`s `lower high tide` should not
reach minor flood stage. However, unless these water level
anomolies lower more substantially later tonight, minor flood
levels will still be reached on the tidal lower Delaware,
including at Burlington and Philadelphia, for the Saturday
morning high tide around 5 to 630 AM. It seems doubtful that
water levels will lower quick enough, with continued runoff from
tributary streams, creeks, and rivers. However, in any case,
the water levels will not be nearly as high as what was
experienced early Friday morning.

Heading through the rest of the weekend, with both astronomical
tides lowering and continued runoff and drainage of the rivers
and bays out to sea, the coastal flood threat should finally
end.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory from 4 AM to 9 AM EDT Saturday for
     PAZ070-071-106.
NJ...Coastal Flood Advisory from 4 AM to 9 AM EDT Saturday for
     NJZ017>019.
     Coastal Flood Advisory until midnight EDT tonight for NJZ020-
     026.
DE...Coastal Flood Advisory until 8 PM EDT this evening for DEZ003-
     004.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ430-431-
     450>454.
     Gale Warning from 6 AM to 6 PM EDT Saturday for ANZ430-431-
     450>454.
     Small Craft Advisory until 6 PM EDT Saturday for ANZ455.

&&

$$

SYNOPSIS...RCM/Robertson
NEAR TERM...DeSilva/RCM
SHORT TERM...Robertson
LONG TERM...Robertson
AVIATION...DeSilva/RCM/Robertson
MARINE...DeSilva/RCM/Robertson
TIDES/COASTAL FLOODING...Dodd