Forecast Discussion

311
FXUS61 KPHI 040228
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1028 PM EDT Sat May 3 2025

.SYNOPSIS...
A cold front will gradually work its way into the region tonight
into Sunday before settling just to our south into Monday. An
expansive upper level system over the Ohio Valley will direct
several pieces of energy across our area through Tuesday resulting
in unsettled weather. The system will gradually move out of the
region Tuesday night and Wednesday. A cold front will then move
across our region Thursday into Friday with high pressure building
nearby during Saturday.

&&

.NEAR TERM /THROUGH SUNDAY/...
The remainder of Severe Thunderstorm Watch has been cancelled. Clusters
of showers and storms continue to move through the area near
and especially NW of the I-95 corridor. However, CAPE values and
low-level lapse rates are beginning to wane as we move further
away from sunset which has decreased the risk for any lingering
severe storms. The front to our north should start to nudge
back slightly north overnight. As a result, the overnight
convection will continue to diminish from south to north. It
will be a mild and humid night with lows for most areas not
dropping below the 60s.

By sunrise Sunday, a large area of low pressure both at the
surface and aloft will be slowly churning over the midwest.
Latest indications are that there will be a wave of upper level
energy associated with this system that will pivot through the
area from SW to NE through roughly the 12-18z timeframe. This
means it actually looks to be the mid morning into the early
afternoon that will be more favored for widespread rain/showers,
possibly heavy at times. Cloud cover will be quite widespread
by this time and also due to the earlier timing during the day
the severe weather threat looks low as instability may be quite
minimal. That said, PWATs around 1.5 inches along with nearly
saturated profiles could still result in some localized flooding
and even flash flooding. By the latter half of the afternoon,
showers/storms look to diminish from SW to NE meaning the end of
the day could actually be mostly dry. Cloud cover along with
more marine influence due to the flow being more SE will keep
it cooler compared to today with highs generally in the 70s.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
Unsettled as spokes of energy move through ahead of a closed low.

A closed low will become nearly stationary over the Ohio Valley
through Monday night, before it shifts northeastward during Tuesday
and Tuesday night. Surface low pressure will meander under the
closed low in the Ohio Valley and then travel with it through
Tuesday night. A cold front looks to settle across our area into
Sunday before shifting just to our south into Monday. Shortwave
energy rotating around the closed low will lead to times of showers
and some thunderstorms. This should result in clouds dominating and
with the winds turning southeasterly, the instability looks to be
limited. The southeasterly flow should lead to a more focused area
of some heavier showers at times across areas northwest of the I-95
corridor. It is in these areas where several inches of rain may fall
through Tuesday night.

Showers and some thunderstorms should tend to increase at times
Sunday night through late Monday as some stronger forcing arrives.
While some elevated instability will lead to isolated to scattered
thunderstorms, the lower instability due to onshore flow should
significantly limit the severe thunderstorm risk. Given deeper
moisture occurring and that showers and thunder should occur within
clusters with even some locally training cells, there is a local
flash flood risk. This will be greatest where heavier cores train
over the same area tied with higher hourly rainfall rates. There
should be breaks in between rounds of more organized convection, and
this should limit the flash flood threat overall. May concern is in
the urbanized areas where higher hourly rainfall rates will result
in more efficient runoff. High temperatures both Monday and Tuesday
are forecast to be in the 60s and 70s across the region.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Summary...Mild to warm conditions, although cooling may occur to end
the week for a time. Precipitation chances are forecast to be lower.

Synoptic Overview...A closed low is forecast to be weakening and
lifting out of the Northeast during Wednesday. Another upper-level
trough looks to be quick on its heels as it moves into the Northeast
Thursday, which may amplify quite a bit Friday before starting to
lift out into Saturday. At the surface, a cold front is forecast to
cross our area late Wednesday into Thursday then high pressure
starts to build nearby later Friday into Saturday.

For Wednesday and Thursday...A closed low is forecast to weaken and
open up during Wednesday as it lifts across the Northeast. This will
continue to take a cold front offshore with weak high pressure well
to our southwest. Another upper-level trough however looks to
quickly move into the Northeast Thursday and this should usher in
another cold front later Wednesday night into Thursday across our
area. Some shower and thunderstorm activity may accompany this
front, however the details are a bit uncertain as the timing will
play a role especiallly regarding the magnitude of the instability.
High temperatures each afternoon are forecast to be in the low to
mid 70s, although cooler in the higher elevations and right along
the coast.

For Friday and Saturday...The aforementioned upper-level trough may
amplify quite a bit across the Northeast and Mid-Atlantic regions
during Friday. This would deliver a much cooler air mass across the
area and with the colder air aloft there is some potential for some
instability driven showers during the day Friday. If the trough does
indeed become rather amplified with a much colder air mass aloft,
then some low-topped convection would be possible pending enough
instability (some hail potential?). The trough looks to lift out
during Saturday with moderating temperatures.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...Scattered showers/storms linger this evening and
again will be focused mainly near and especially north of the
I-95 terminals. Once again, sub VFR likely if any storms move
over TAF sites but otherwise VFR through most of the evening.
Ceilings will begin to lower towards 12Z from west to east, with
MVFR or perhaps IFR becoming increasingly likely. South to SE
winds around 5 to 10 knots. Moderate confidence.

Sunday...Rain/showers fairly widespread in the morning through
the early afternoon along with some possible embedded storms.
Mainly MVFR cigs with even some times of IFR possible. South to
SE winds around 10 knots. Moderate confidence.

Outlook...

Sunday night through Tuesday...Periods of sub-VFR conditions with
several rounds of showers and some thunderstorms.

Wednesday and Thursday...Mainly VFR.

&&

.MARINE...
A Small Craft Advisory remains in effect for the Atlantic
coastal waters to 7 AM Sunday. South wind 15-20 kt with gusts
to 30 kt and seas 4-6 ft expected.

For Sunday, conditions will still be right around or just below
marginal Small Craft Advisory levels with south to southeast
winds around 15 to 20 knots and seas 4-5 feet. This means it`s
possible the Small Craft Advisory may need to be extended.

Outlook...

Sunday night...The conditions are anticipated to be below Small
Craft Advisory criteria.

Monday and Tuesday...Small Craft Advisory conditions possible.

Wednesday...The conditions are anticipated to be below Small Craft
Advisory criteria.

Thursday...Small Craft Advisory conditions may develop later at
night, especially on the ocean zones.

&&

.HYDROLOGY...
Several waves of wet weather look to begin through tonight and
persist into Tuesday. Several inches of rain may fall in some
locations, however timing and location will be critical to determine
if any flooding issues arise. If higher convective hourly rainfall
rates occur in any location in a short period of time, especially
over the urbanized areas, there will be an increasing localized
flash flooding risk due to more efficient runoff. Fortunately, we
are coming off an extended dry spell, particularly northwest of I-95
where indications suggest the heaviest rain may end up falling. For
the time being, we will continue to monitor trends in the guidance.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 7 AM EDT Sunday for ANZ450>455.

&&

$$

SYNOPSIS...Gorse/RCM
NEAR TERM...AKL/Cooper/Fitzsimmons
SHORT TERM...Gorse/RCM
LONG TERM...Gorse
AVIATION...Fitzsimmons/Gorse/Guzzo
MARINE...Fitzsimmons/Gorse
HYDROLOGY...WFO PHI

Latest Observation at Wilmington

Data at: 0000 UTC 03 Sep 2023

New Castle County Hourly Weather Forecast

KDOX Radar Loop

KDIX Radar Loop

Visible Satellite

Visible Loop

Infrared Satellite

Infrared Loop

Severe Weather Outlooks

Useful Links

Event Weather Dashboard

Graphical Hazardous Weather Outlook

Experimental WBGT Forecast

Emergency Manager Briefing

NWS Mount Holly Winter Weather Page

Current Hazard Products from NWS Mount Holly

Local Forecast Graphics