000
FXUS61 KPHI 151101
AFDPHI

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

.SYNOPSIS...
A slow moving cold front will drop south across the area through the
course of the day 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/...
Overall, the near term forecast remains on track with
temperatures early this morning are mainly in the 50s across the
region.

Heading into the daytime hours, conditions will be dry
regionwide through the early afternoon with just a few cirrus
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 and SPC does have a portion of
the Eastern Shore of Maryland and southern Delaware in a
MARGINAL risk for severe storms. However, the greater risk will
be south of the region.

Any showers and storms that do form will begin to 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 /12Z 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