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000
FXUS61 KPHI 250536
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
136 AM EDT Thu Apr 25 2024

.SYNOPSIS...
High pressure arrives from the Great Lakes today before
shifting to our northeast and east on Friday. A warm front
should lift north of our area later Saturday, then a cold front
gradually approaches later Monday before moving across our area
later Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Lateset analysis shows the cold front has mostly cleared the
region, but winds being relatively weak behind the front plus
some lingering clouds, temps have been slow to drop. Have
maintained freeze and frost headlines as inherited for early
this morning, but temps will have to drop quite a bit more for
them to verify. May trim back headlines in a few hours if trends
remain above expectations.

Weak shortwave passing by this morning likely keeps some clouds
around from Philly on southward for a good chunk of the day, and
in fact there could be a stray shower, most likely over the
Delmarva but a small chance even in southern NJ. Looks like any
showers would end before noon, and we should gradually start to
dry out and clear out more late in the day. While the cold
advection has lagged, still expect today to be notably cooler
than yesterday, with highs mostly in the 50s.

High pressure builds to the north tonight with the gradient
slacking off enough. With drier air in place by then along with
clear skies, expect radiational cooling to maximize. Thus, have
leaned hard on the colder guidance and issued a freeze watch for
a large chunk of the region especially north and east of
Philadelphia. Areas further south and west look more tricky but
still likely need frost advisories for these areas. Lows overall
in the 30s, with near or below 30 in the Freeze Watch area and
Poconos but closer to mid 30s in the urban centers and Delmarva.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
An upper-level trough is forecast to shift to our east to start
Friday. Strong surface high pressure shifts off the New England
coast during Friday.

After a cold start Friday morning, the surface flow should
start to become more southeast to even south-southeast. This
will still keep some marine influence across the area, however
the air mass is forecast to start modifying and therefore high
temperatures will be in the upper 50s to low 60s, a bit higher
compared to Thursday. It will still be cooler though closer to
the coast given the onshore flow. Another chilly night Friday
night, though slightly warmer compared to Thursday night as well
with low temperatures in the upper 30s to low 40s. This would be
sufficiently warm enough to mitigate widespread frost
development, but patchy frost remains possible.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Summary...A significant warm-up probable over the weekend and
early next week. Some shower chances later in the weekend and/or
early next week.

Synoptic Overview...A building ridge arrives from the west as
an upper-level trough lifts across the Plains and into the
Midwest through Monday. As the influence of the upper-level
trough gets closer late Monday and Tuesday, the ridge shifts to
our east. The timing of this however is less certain as the
upper-level trough in the Plains may become a closed low which
tend to be slower moving (may be two separate systems). This
will also have an impact on our precipitation chances Sunday
through Wednesday. The overall pattern though continues to
suggest that a much warmer air mass will overspread our region
Sunday through the middle of next week.

For Saturday...A building ridge starts to arrive from the west
and this will initially keep a cool air mass across our region.
However, some warm air advection starts as more of a southerly
return flow starts initiates. In addition, a warm front should
lift to our north later Saturday. While a few showers cannot be
ruled out with this warm front, mainly northwest of the I-95
urban corridor, the probability looks to be on the low side at
this point. Cloud cover should dominate the sky during at least
a portion of Saturday due to some increasing warm air advection
and some increase in moisture ahead of and with the warm front.
The timing of this warm front looks to be driven by a lead
upper- level trough or closed low that lifts across the Midwest
which also has a surface low with it.

For Sunday through Wednesday...As an upper-level trough
continues to lift up across the Plains and Midwest, the
downstream ridge axis slides across our region Sunday and Monday
before shifting offshore into Tuesday. While the initial trough
looks to continue to lift to the northeast across eastern
Canada, if the secondary trough forms, it may not push through
our area until Wednesday. Surface low pressure tracks across the
Great Lakes and into adjacent Canada Monday into Tuesday, and
its associated cold front approaches our area Monday night. The
actual cold front looks like it will not slide across our area
until later Tuesday. The details however will depend on the
timing and amplification of the trough. In addition, high
pressure sliding east of Hudson Bay Canada Monday into Tuesday
may send a cold front down across New England and closer to our
area. While this front may settle into at least our northern
areas Monday night into Tuesday, it should not get too far south
given the continued southerly flow ahead of the aforementioned
trough from the west. Plenty of warm air with increasing dew
points are therefore currently forecast across the area, with
high temperatures for much of the area in the 70s to even some
low to mid 80s. The surface flow however looks more south or
even southeast at times and this will keep it several degrees
cooler at the coastal communities compared to farther inland.
There is a chance for some showers and thunderstorms, especially
Tuesday and Tuesday night, with PoPs mainly in the 30-50% range
during this period. With the possibility of a secondary front,
slight chance PoPs (15-25%) linger into Wednesday.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Through today...VFR. Northerly winds generally 5 to 10 knots
before diminishing late day. High confidence.

Tonight...VFR. Winds becoming more northeasterly but slacking
off to 5 kts or less overnight.

Outlook...

Friday...VFR.

Saturday...A period of near MVFR ceilings possible, most likely
Saturday night, otherwise mainly VFR.

Sunday and Monday...VFR conditions anticipated.

&&

.MARINE...
Seas will remain elevated through today before slowly starting
to come down tonight. For this reason, the Small Craft Advisory
was extended to 22z today for our northern ocean zone off the
coast of Monmouth County with it running until 10z Friday for
the remaining ocean zones. Northeast winds will mostly be sub
SCA.

Outlook...

Friday through Monday...The conditions are anticipated to be
below Small Craft Advisory criteria.

&&

.FIRE WEATHER...
RH`s across much of the region will get quite low today, and
we`ve had little rain now for a couple of weeks, allowing fine
fuels to dry. While winds won`t likely be up to Red Flag
Criteria, there may be a need for a Special Weather Statement,
which will be firmed up after morning coordination with our
state partners.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Freeze Warning until 9 AM EDT this morning for PAZ061-062.
     Freeze Watch from late tonight through Friday morning for
     PAZ061-062-103-105-106.
     Frost Advisory until 9 AM EDT this morning for PAZ060-105.
NJ...Freeze Warning until 9 AM EDT this morning for NJZ001-007-008.
     Freeze Watch from late tonight through Friday morning for
     NJZ001-007>010-012-013-015>022-027.
     Frost Advisory until 9 AM EDT this morning for NJZ009.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ450.
     Small Craft Advisory until 6 AM EDT Friday for ANZ451>455.

&&

$$

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