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000
FXUS61 KPHI 151357
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
957 AM EDT Mon Apr 15 2024

.SYNOPSIS...
A slow moving front across eastern Pennsylvania and New Jersey this
morning will amble south towards Delmarva later today. High pressure
builds back in tonight through Tuesday, before a series of frontal
boundaries and low pressure systems affect the East coast Wednesday
through early next weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
A few adjustments for the morning update. Added some clouds and
slightly higher pops for the areas south of the front with the
pace of the front a bit slower than fcsted. Overall, temps and
winds looked good, so few updates there. From before...

Heading into the daytime hours, conditions will be dry regionwide
through the early afternoon with just scattered Ci/Ac clouds around.
This along with the lagging cold front will allow temperatures
to rise into the mid-upper 70s for most locations to even low
80s in Delmarva (cooler at higher elevations and along the coast).
Ahead of the front, PWATs will also still be somewhat elevated,
generally around 1 inch or so. These ingredients will provide the
fuel for some more scattered showers and thunderstorms this afternoon
and evening, though mainly limited to Delmarva and far South Jersey
as the front will have begun to pass through the northern half of
the area. CAM ensemble guidance indicates 400-600 J/kg of CAPE with
less CIN compared to yesterday. However, the low-level winds are
significantly weaker compared to yesterday. The result is a more
typical setup for our region where stronger thunderstorms will
be capable of producing 40-50 mph wind gusts and some small hail.
Isolated severe-level hail or straight-line wind gusts cannot be
completely ruled out.

The SPC has made a subtle northward shift with the Day1 outlooks
at 13Z (9AM) with the Slight risk bumping into SW corner of
Delaware and the Marginal risk floating back across most of the
rest of Delaware and SEmost NJ. General TSTMs are in for areas
south of Belmar-Trenton (NJ) and Downingtown (PA).

Any showers and storms that do form later today will dissipate later
this evening with the loss of daytime heating and increasing subsidence
as high pressure begins to build into the region. Thus, the
remainder of Monday night and Tuesday will be dry. Temperatures
will fall into the upper 40s to low 50s Monday night before
rebounding into the upper 60s to low 70s on Tuesday.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
In the mid an upper levels, a short wave ridge is expected to slide
eastward toward our region by Tuesday night. This should limit
coverage of showers on Tuesday night despite a warm front
approaching from the south.

By Wednesday however, the shortwave ridge will weakens the next
closed low approaches from the west, leading to increasing chances
for showers though the day. Thanks in large part to the warm front
in the region, there will likely be a robust temperature inversion
through the day, resulting in limited instability. Therefore, not
expecting any thunderstorms at this time.

The closed low and a trailing cold front continues to approach the
region Wednesday night into Thursday. Consequently, there are
chances for widespread showers and thunderstorms in the Wednesday
night/Thursday period. As far as thunderstorms, instability,
especially surface based instability may remain limited through this
period, so it is uncertain how widespread the coverage of storms
will be. At this point, it appears as if we are likely to have
widespread showers with some embedded thunderstorms, primarily late
Wednesday night into Thursday morning, though there still remains
quite a bit of uncertainty with the timing.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Tranquil weather should return again, albeit briefly, as the low
departs our region Thursday night into Friday, before the next cold
front approaches to start the weekend. At this point, the forecast
has rain chances almost throughout this period (Friday night through
Sunday), but it is unlikely to be a washout through the period,
rather there remains uncertainty in the exact timing of the cold
front. Once the cold front passes, we should have drying conditions.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Monday...Prevailing VFR with fair weather for most terminals.
An afternoon shower possible for MIV/ACY which could briefly
bring sub- VFR conditions. Mainly west-northwest winds around 10
kts with gusts up to 20 kts, decreasing to 5-10 kts overnight.
Moderate confidence.

Outlook...

Tuesday through Tuesday night...VFR expected.

Wednesday through Thursday...There is a good chance (50 to 60
percent) for sub VFR conditions at times due to stratus and showers.
The best chances for this look to be overnight Wednesday night into
Thursday morning.

Thursday night and Friday...VFR likely, but a brief period of sub-
VFR is possible (20%) especially Friday.

&&

.MARINE...
Seas have decreased below 5 feet and therefore, the SCA was
cancelled. Sub-SCA conditions will persist through the rest of
the period into Monday night with lighter W to SW winds. Mostly
fair weather conditions but some scattered showers or a
thunderstorm are possible this afternoon and evening,
particularly for Atlantic Coastal waters south of Great Egg
Inlet and on the Delaware Bay.

Outlook...

Tuesday through Wednesday...winds and seas should stay below SCA
criteria.

Wednesday night through Friday...SCA conditions are likely (60%) for
at least a portion of this period and especially over our northern
ocean zones as winds and seas build.

&&

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

&&

$$

SYNOPSIS...Fitzsimmons/Johnson
NEAR TERM...AKL
SHORT TERM...Fitzsimmons/Johnson
LONG TERM...Fitzsimmons/Johnson
AVIATION...AKL/Fitzsimmons
MARINE...AKL/Fitzsimmons