485
FXUS61 KPHI 141004
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
604 AM EDT Mon Apr 14 2025

.SYNOPSIS...
A warm front lifts through today, followed by a cold front passing
late tonight into Tuesday. A secondary cold front crosses through
late Tuesday night. High pressure returns on Wednesday and persists
into Friday. Another disturbance and sequence of fronts approach the
area late Friday into next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Increasing clouds this morning as a warm front approaches the region
from the southwest ahead of a closed low over the Great Lakes.
Temperatures this afternoon will bounce back into the mid 60s to
around 70 for the high as warm southerly flow prevails through the
day.

Come Monday evening, the closed low over the Great Lakes will shift
into southern Ontario and Quebec, dragging a cold front across the
Mid Atlantic. Anticipating widespread showers across the region with
this frontal passage along with embedded thunderstorms, mainly south
of the I-78 corridor with the greatest chance across the Delmarva
and southern NJ. Forecast soundings suggest that instability will be
limited and/or elevated in nature mainly due to the loss of diurnal
heating and a strong surface inversion. There will be a decent
amount of deep layer shear in place, around 40-50 kts in the 0-6km
layer, to support a damaging wind threat. That said, given the
surface inversion in place, the likelihood of this is rather low.
With this in mind, the Storm Prediction Center has maintained their
outlook with a general thunderstorm risk for our entire area with
portions of the Delmarva in a Marginal Risk for severe
thunderstorms. Total QPF will range from 0.10-0.25" with the highest
amounts further south. Lows on Monday night will range in the upper
40s to mid 50s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
By Tuesday, the area will be fully situated under the upper level
trough and influenced by cyclonic flow. With enough moisture still
hanging around and with a few impulses spiraling around the upper
level low, cannot rule out a few showers during the day on Tuesday
(best chance will be near the coast in the morning and in the
Poconos in the afternoon). With the afternoon round, cannot rule out
a few convective cells capable of producing some small hail/graupel
as there will be some instability combined with favorable low and
mid-level lapse rates, along with lower freezing levels. Best
dynamics for a few power showers will be for the Poconos and far
northern New Jersey. Not expecting severe weather though given low
instability and shear.

With a mix of sun and clouds around, expect highs in the upper 50s
to mid 60s and gusty winds upwards of 30 to 40 mph in the afternoon.
A stronger impulse will cross through the area on Tuesday night,
which will result in a secondary cold front to pass through at the
surface. This front will pass through dry however. Temperatures on
Tuesday Night will be in the upper 30s and low 40s, with winds
staying elevated, but much less compared to daytime Tuesday and
Wednesday.

Once the secondary front passes, a cooler/drier airmass will return
to the region with gusty winds continuing into Wednesday. Expect
wind gusts to be a touch less than the day prior, most likely in the
25-35 MPH range. Highs will be seasonably cool for mid-April, with
highs only in the 40s and 50s under a mix of sun and clouds.

Winds diminish quickly on Wednesday Night as the gradient weakens
with high pressure building in. While skies will be mostly clear,
winds will stay elevated around 10 MPH, enough to prevent
temperatures from bottoming out completely. Lows will be in the mid
to upper 30s, with some spots along and north of I-78 getting near
or below freezing. This will be the coldest night of the week.
Thinking it will dry enough to prevent frost from developing, but if
temperatures fall much further than currently forecast, we may need
some freeze headlines for areas where the Frost/Freeze program is
active (south of I-78). This will be the main thing to watch during
the middle of the week.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
The Thursday through Friday period still appears to remain quite
benign as expansive high pressure settles over much of the Eastern
US. This will allow dry conditions and sunny/clear skies to occur
for much of the period, before increasing clouds return later on
Friday. For highs on Thursday and Friday, we`ll begin to see some
moderation with highs in the upper 50s to low 60s on Thursday,
increasing to the mid to upper 60s for Friday. Lows on Thursday
Night should be in the mid to upper 30s/low 40s.

Moving forward into Friday night and next weekend, the period
overall looks to be a bit unsettled. The next low pressure system
will begin to approach as it tracks through the Great Lakes. This
will cause another sequence of fronts to cross through the area.
General consensus is that a warm front will cross though late Friday
night into Saturday with a cold frontal passage on Saturday night
into Sunday. Accompanied with these fronts will likely be some rain
showers so have included a 20-50% chance of showers for the Friday
night through Saturday night period. After the cold frontal passage,
we should begin to dry out for Sunday. In terms of temperatures,
anticipate above normal temperatures throughout the period, with
peak temperatures occuring on Saturday which look to be well into
the 70s. Temperatures for the back half of the weekend and into next
week look to go back toward more seasonal levels with the passage of
the cold front on Saturday Night.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Monday...VFR. SCT/BKN clouds around 10 kft will likely move in by
early afternoon at all terminals. Wind becoming south-southwest
around 5-10 kts. High confidence.

Monday night...Sub-VFR conditions possible with likely rain showers
and perhaps a few isolated thunderstorms. South to west-southwest
winds 10 kts or less with stronger gusts possible in thunderstorms.
Low confidence.

Outlook...

Tuesday...Primarily VFR, though sub-VFR conditions possible with
showers (20-40% chance SHRA). Gusty west winds 15-20 kt gusting 25-
35 kt.

Tuesday Night...VFR. Westerly wind gusts around 20 kt.

Wednesday...VFR. Westerly wind gusts 20-30 kt.

Wednesday Night through Friday..VFR. No significant weather.

&&

.MARINE...
Winds and seas continue to diminish and are expected to stay
below Small Craft Advisory criteria through Monday night. Rain
showers likely with an isolated thunderstorm possible Monday
evening into the overnight.

Outlook...

Tuesday through Wednesday...A Small Craft Advisory is in effect
beginning at 10 AM on Delaware Bay and 1 PM on the ocean zones.
Westerly wind gusts of 25-30 kt expected with a few higher gusts
possible, but not getting to gale force. Seas 3 to 5 feet.

Wednesday Night...The Small Craft Advisory may need to be extended
as wind gusts diminish but could remain near 25 kt. Confidence was
not high enough to extend this far yet.

Thursday through Friday...No marine headlines expected.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 10 AM Tuesday to 6 PM EDT Wednesday
     for ANZ430-431.
     Small Craft Advisory from 1 PM Tuesday to 6 PM EDT Wednesday
     for ANZ450>455.

&&

$$

SYNOPSIS...DeSilva/Hoeflich
NEAR TERM...MJL
SHORT TERM...DeSilva/Hoeflich
LONG TERM...DeSilva/Hoeflich
AVIATION...Hoeflich/MJL
MARINE...Hoeflich/MJL