Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 171922
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
322 PM EDT Sun Mar 17 2024

.SYNOPSIS...
A reinforcing cold front moves through on Monday. Several upper
level disturbances will pass through the region this week as
surface high pressure builds to the west. Developing low
pressure approaches for the end of the week and weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
Some milder air hanging on this afternoon, however the main
cooling trend starts tonight and Monday.

An upper-level trough from the Midwest and Great Lakes to
adjacent Canada will slowly shift eastward through tonight. This
trough then settles more over our region by later Monday. The
first cold front cleared our region this morning and is bringing
in cooler air mostly aloft initially. This coupled with a still
mild boundary layer and stronger flow is resulting in a gusty
wind this afternoon. The mixing is forecast to rapidly shrink
this evening and therefore the winds will diminish quite a bit
as we go through tonight. This will set the stage for a chillier
night as temperatures drop into the 30s overnight (even some
upper 20s in the Poconos). The cold air advection combined with
the milder boundary layer is producing stratocumulus within the
west to northwest flow. The bulk of this is near and north of
I-78 with less farther south given downsloping flow and drier
air getting entrained. This cloudiness is expected to mostly
dissipate going into and through this evening, however a some
higher level clouds should be around given strong mid to high
level flow ahead of the trough. In addition, mostly channelized
vorticity within the flow ahead of the upper-level trough may
result in some sprinkles or a brief light rain shower which
transitions to some flurries or a brief snow shower later this
afternoon and this evening, mainly in the Pocono region.

As we go through Monday, as mentioned above the upper-level
trough axis starts to settle over our area by later in the day.
This will deliver colder air with daytime high temperatures
being much closer to average. Stronger flow remains and with
deepening mixing occurring, a brisk west-northwest wind will
once again develop during the course of the day. As the trough
axis arrives, a secondary cold front will move through and this
will deliver even drier low-level air as dew points drop into
the teens for much of the area. There could also be some
flurries or a snow shower mainly in the Pocono region. It will
definitely feel colder as temperatures step down some more and
with the breeze added in. Some stratocumulus is also expected to
be around.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Weak reinforcing cold front and potent upper trough axis will
cross the region Monday evening. Some CAMs suggest there could
be some flurries or snow showers with it, particularly across
northern New Jersey and the Poconos, but other guidance is dry,
so for now maintain a dry forecast. We`ll be watching this
potential closely. Otherwise, breezy and chilly conditions will
prevail with temperatures running slightly below normal, but
notably colder than recent days, with wind chills down in the
20s for most and teens in the Poconos. Lows mostly near or below
freezing.

Breezy and chilly conditions continue Tuesday, with the cold
advection behind the front pushing temps several degrees lower
than Monday. This looks like the first day with high
temperatures notably below normal for weeks, with most areas
staying in the 40s. While sunshine may start day, another
passing upper trough likely helps instigate more cloud cover as
the day wears on, but right now the chance of any precip looks
minimal.

A weak warm front will then try to lift into the region Tuesday
night. This will keep clouds around and could help instigate a
few flurries or snow showers i,
though it looks majority rain, but tn the Poconos. Lows should stay a
little milder, generally above freezing except in the Poconos.

Modest warm surge develops ahead of another approaching cold
front on Wednesday. This should help elevate temps back to near
normal, with 50s more widespread, but by later in the day, a few
showers may develop as the front approaches and then passes.
These could be snow in the Poconos, but look more likely to be
rain elsewhere. With the front approaching and then passing
westerly wind could get pretty gusty, with peak gusts possibly
30-40 mph.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Cold advection is fairly quick behind the front Wednesday
evening. Temps will likely drop below freezing again across the
area, with upper teens possible in the Poconos. With winds still
possibly gusting above 30 mph at least in the evening, wind
chills may be in the teens at times across much of the area,
perhaps even single digits in the Poconos.

High pressure is finally building in on Thursday, but the winds
will stay elevated at least through midday, and this may keep
wind chills quite low in the morning. By afternoon, the pressure
gradient relaxes and winds should start to drop off towards
evening. The airmass Thursday looks slightly colder than
Tuesday, making Thursday likely the coldest day of the week and
quite possibly the coldest day of March this year.

High pressure slides across the region Thursday night, and we
should see lighter winds with at least partially clear skies.
This should allow decent radiational cooling, so we could also
make a run at the coldest night of the month as well, though
this will be competing against March 1st which was quite chilly
in outlying areas.

Another wave of low pressure then quickly approaches for Friday,
with a chilly morning with increasing clouds followed by a
chance of showers by late day and at night. If there is enough
cool, dry air remaining, its possible precip could being with
some mixed precip or snow, but still highly uncertain, and it
looks likely as the system passes at night into early Saturday
that enough warm air will be drawn northward for most areas to
go over to rain. Still, in a season with below normal wintry
precip, any frozen precip coming down this late in the year will
feel unusual, even though it isn`t particularly.

After that, uncertainty presides over the weekend as a low
pressure appears likely to develop across the southeastern US
coast. A track northward is possible at some point, but timing
that track and its exact direction is quite uncertain. Thus,
while precipitation odds aren`t great over the weekend they
certainly aren`t zero. Will need to watch this potential system.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

This afternoon...VFR. West-northwest winds around 15 knots with
gusts to around 25 knots. Moderate confidence.

Tonight...VFR. West-northwest winds diminishing to around 5
knots. High confidence.

Monday...VFR. West-northwest winds 5-10 knots increasing to
around 15 knots with gusts to around 25 knots. Moderate
confidence.

Outlook...
Tuesday through Friday...VFR overall. Could be a few showers
Wednesday afternoon and then Friday afternoon which could lower
cats. Otherwise, the main concern through the week will just be
persistent gusty west to northwest winds, which could gust up to
35 kts at times Wednesday.

&&

.MARINE...
Offshore flow will continue through Monday, however the better
mixing looks to occur over land especially during the daytime
hours. While the winds are expected to increase some through
Monday, the conditions are anticipated to be below Small Craft
Advisory criteria overall.

Outlook...
SCA conditions likely Tuesday through Thursday with persistent
northwesterly winds. Could touch Gales at times, most likely
sometime Wednesday or Wednesday night. Conditions probably
subside below SCA levels Friday.

&&

.FIRE WEATHER...
A few rain/snow showers or sprinkles/flurries possible across
the Poconos through the next several days. Aside from that, dry
conditions. Although most of the area is above normal for
precipitation since March 1, it has been a week since the last
significant rainfall, and no significant rainfall is expected
this week.

Min RH values this week will generally range from 25 to 35
percent, and stronger westerly flow occurs over the area as
well with winds generally 15 to 20 mph with gusts 25 to 30 mph.

The day of highest concern looks to be Thursday, where surface
dew points drop into the upper single digits to low teens. Min
RH values may be as low as 20 to 25 percent, and west to
northwest winds could gust as high as 30 to 35 mph. By then, it
will be almost 2 weeks since the last significant rainfall.

Depending on how fast and how efficiently fine fuels dry out
will add to possible concerns for the rapid spread of any fires
that may develop.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

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


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