Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 170151
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
951 PM EDT Sat Mar 16 2024

.SYNOPSIS...
Weak high pressure moves offshore tonight. A weak cold front passes
through on Sunday followed by a secondary cold front passing through
on Monday. A few upper level disturbances will pass north of the
area through the mid-week period as surface high pressure builds to
the west. Low pressure approaches towards the end of week into next
weekend.

&&

.NEAR TERM /THROUGH SUNDAY/...
Overall, the term forecast remains on track. A zonal flow aloft
will back later tonight and especially Sunday as a strong
upper- level trough approaches from the west. At the surface,
weak high pressure will continue shifting offshore to our
southeast during the overnight hours tonight.

Much drier air and enough subsidence is resulting in a mainly clear
sky which will continue through about the first half of
tonight. As the aforementioned upper-level trough gradually
shifts south and eastward across the Great Lakes and adjacent
Canada, surface low pressure will track well north of our area
overnight and Sunday. An associated cold front however will move
across our region Sunday morning. The main forcing for ascent
is forecast to lift north of our area, however a period of
stronger frontal forcing to our west should result in a band of
rain or showers with the front. This however should weaken with
a southern extent as it shifts eastward overnight and Sunday
morning as the main forcing peels off to our north. There may be
a secondary area of convergence or lift glancing our far
southeastern zones early Sunday morning as a southwesterly low-
level jet of 40-50 knots crosses our area. Therefore, some
showers are possible later tonight and Sunday morning for mainly
the northern to far western areas and near our far southeastern
zones. Any rainfall looks to be light.

Given the expectation of an increase in clouds overnight and
the arrival of a southwesterly low-level jet, temperatures
should tend to level off or even rise some overnight especially
across the coastal plain.

As we go through Sunday, a positive-tilt upper-level trough will
gradually be getting closer to our area. This will push the
aforementioned cold front offshore during the morning with some cold
air advection increasing in its wake. The core of the colder air
however hangs back farther west beneath the upper-level trough.
While high temperatures will once again be above average, a little
more cooling will occur given the cold front that clears the area. A
much drier air mass however will advect across the region, and with
deeper mixing during peak heating the dew points will drop into the
20s for much of our area. A tightening pressure gradient combined
with the cold air advection aloft will result in deeper mixing
through the day and therefore a gusty northwesterly wind is
expected. The cloud cover should thin out at least some, however the
model forecast soundings indicate at least some stratocumulus
development possible within the northwesterly cold air advection
regime.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
Upper level troughing will be slowly pushing into the area Sunday
night and Monday with the main trough axis pushing through Monday
evening. A secondary shortwave crosses the region later Tuesday
but its not nearly as deep. At the surface, low pressure to the
northeast and high pressure building in from the west will
provide a northwesterly gradient through the period, with cold
advection much of the time. With the troughs passing, the chance
of some snow showers will exist in the Poconos, particularly
Monday night and again late Tuesday. However, the air mass will
be rather dry, so it may be hard to squeeze out measurable snow.
Winds will be gusty from the northwest on Monday with gusts of
20-30 mph, but by Tuesday the gradient tightens further and we
may have gusts of 30-40 mph area- wide. Combined with the much
colder temperatures, and we will really feel the chill, even
though highs aren`t going to be all that below normal... just
much below what we`ve had lately. Lows won`t be that much
colder, though, since the gradient and some stratocumulus likely
holds them up somewhat. Highs will be near 50 on Monday and
mostly 40s Tuesday, with lows in the 30s Sunday night and near
30 on Monday night.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
An upper level trough will be located over the Northeast and Mid-
Atlantic states through Wednesday night. Several impulses embedded
in the upper flow will pass north of the area during this time.
These impulses may allow for periods of rain/snow showers to occur
across the Poconos and northern New Jersey during the Tuesday night
and Wednesday timeframe as a cold front crosses the area. Elsewhere,
fair weather is expected with seasonable temperatures.

High pressure then approaches from the west, building over the Great
Lakes region on Thursday before shifting offshore on Friday. Quiet
and seasonable weather is expected.

Attention turns to Friday night into next weekend where a southern
stream low pressure system will be located near the Southeast US.
Forecast guidance varies greatly with the details on the track of
this system whether it tracks out to sea or up the coast. For this
reason, have carried the chance of showers wording into the start of
next weekend.

&&

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

Tonight...VFR, with clouds increasing overnight. There is a low
chance (about 20-30 percent) for a few showers for KRDG to KABE
to north of KTTN after 06z. Southwest surface winds diminishing
to mainly less than 10 knots. A southwesterly low-level jet of
40-50 knots arrives overnight and that could lead to some low-
level wind shear, however the duration may be limited and
therefore opted to not include a mention. Additionally, the
arrival of the LLJ may result in a slight uptick in wind speeds
to around 10 knots, closer to sunrise. Moderate confidence.

Sunday...VFR ceilings should lift and thin some. A few early
morning showers possible mainly from KRDG to KABE to north of
KTTN. Southwest winds around 10 knots early become west-
northwest and increase to 12-15 knots with gusts up to 25 knots.
Moderate confidence.

Outlook...

Monday and Tuesday...VFR overall. Main concern will be gusty NW winds
which may reach 20-25 kts Monday and 30-35 kts Tuesday. Winds
will be lighter at night and early in the mornings.

Tuesday night...VFR likely. SW winds around 5-10 kt. Moderate
confidence.

Wednesday....VFR likely. SW-W winds around 10-15 kt with gusts up to
25 kt possible. Moderate confidence.

Wednesday night through Thursday...VFR. W-NW winds ranging between
10-20 kt. Moderate confidence.

&&

.MARINE...
Small Craft Advisory issued for the New Jersey coastal waters late
tonight through about mid morning on Sunday. A southwesterly low-
level jet is forecast to move across the area overnight and early
Sunday morning ahead of a cold front. There looks to be enough
mixing beneath an inversion for a period of 25-30 knot gusts. This
appears to be more marginal for the Delaware coastal waters and into
Delaware Bay, therefore held off on an advisory for here at this
point. Seas will also increase for a time, then offshore flow during
Sunday will lower the seas some.

Outlook...

Monday and Tuesday...SCA conditions possible Monday, with gales
possible Tuesday.

Tuesday night...SCA conditions possible early. W winds of 10-20 kt
with gusts up to 25 kt. Seas of 2-4 feet.

Wednesday through Wednesday night...No marine headlines expected,
although marginal SCA conditions possible late Wednesday night. W-NW
winds around 10-15 kt during the day, becoming 15-20 kt at night.
Seas of 2-4 feet.

Thursday...Marginal SCA conditions possible early Thursday. W-NW
winds around 15-20 kt. Seas of 2-4 feet.

&&

.FIRE WEATHER...
While some showers may occur late tonight and Sunday morning mainly
across northeast PA and northwest NJ, a period of dry and
increasingly breezy conditions starts on Sunday and continues
through Wednesday. The minimum relative humidity values lower to
generally 30 to 35 percent during peak heating each day, with west
to northwest winds 15-20 mph and gusts 30-35 mph. The strongest
winds look to occur on Tuesday. The region has received a lot of
rain over the last several weeks, therefore will have to see how the
fuels, especially the fine fuels, dry out.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 2 AM to 10 AM EDT Sunday for
     ANZ450>453.

&&

$$

SYNOPSIS...DeSilva
NEAR TERM...AKL/Gorse
SHORT TERM...RCM
LONG TERM...DeSilva
AVIATION...AKL/DeSilva/Gorse/RCM
MARINE...DeSilva/Gorse/RCM
FIRE WEATHER...


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