213
FXUS61 KPHI 300357
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1157 PM EDT Sat Jun 29 2024

.SYNOPSIS...
A warm front will lift across the region overnight. A cold
front will then move across the area Sunday afternoon and
evening. High pressure builds in Monday through Tuesday before
moving offshore Wednesday. A surface trough arrives on Thursday
as a cold front may approach from the northwest Friday.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 1150 PM, a weakening band of showers and embedded thunder
continues to work its way into and across the I-95 corridor.
The instability continues to weaken with an eastward extent,
therefore some additional weakening is anticipated. Greater
instability remains across Maryland and more lightning is
present on the western side of Chesapeake Bay. Some gradual
weakening of this activity should also occur as it shifts
eastward. Otherwise, some fog overnight especially along the
coast with the higher dew points advecting over the cooler
waters. It will be a warm and muggy overnight.

More active weather is expected Sunday with a variety of impacts.
A warm front approaches from the west this evening and lifts
north through the overnight period. A hot and humid airmass will
be in place through Sunday. A cold front then approaches on
Sunday and works its way through the region Sunday night.

South to southeast flow ahead of the warm front continues to usher
low level moisture across the region. Surface dew points are
currently in the upper 60s to low 70s, and will continue to rise
into the mid and upper 70s behind the passage of the warm
front.

Hot and humid on Sunday as deep southerly flow continues. surface
dew points will be well in the 70s, likely as high as 76 to 78 in
the morning for most of New Jersey, Delmarva, and southeast
Pennsylvania. There may be enough mixing in the afternoon for the
highest dew points to drop to 73 to 76. For the southern Poconos and
Lehigh Valley, surface dew points will be in the upper 60s to around
70. Highs look to get into the upper 80s to low 90s for most of the
area, but there is a chance these temperatures may be a bit too high
as widespread cloud cover may keep temperatures from getting quite
that high. Heat index values will be in the upper 90s to low 100s.
Since the eastern shores of Maryland look to be around 105, will go
ahead and hoist the Heat Advisory for the eastern shores of Maryland
for Sunday.

Pre-frontal trough develops out ahead of the approaching cold front.
Showers and thunderstorms develop with this trough, and
thunderstorms look to be severe Sunday afternoon and Sunday evening.
SB CAPE values will be in excess of 2500 J/kg, generally 2500 to
3500 J/kg, along with 750 to 1000 J/kg of DCAPE. 0-6 km Bulk Shear
will average 35 to 45 kt and PWATs will be up around 2.5 inches.
Once again, damaging winds will be likely with severe thunderstorms,
and frequent lightning and heavy rain also expected. Localized flash
flooding possible, though once again, there should be enough
steering current for storms to be moving fairly quickly.

Thunderstorms may linger over Delmarva through midnight or so.

Cold front moves across the region Sunday night, and a much drier
airmass spreads into the region with surface dew points falling into
the 50s by daybreak.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
In the wake of the cold front on Sunday, a cooler and less
humid air mass will be ushered in, leading to more pleasant and
tranquil conditions Monday and Tuesday. Broad surface high
builds in so, expect dry conditions. High temperatures are
forecast to range from the mid 70s to mid 80s across the region.
A comfortable air mass with dew points in the 50s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Summary...Less humid to start then the heat and humidity spikes
Thursday, followed by a little cooling but remaining humid. Some
convection possible late in the week. Few changes from the
previous forecast.

Synoptic Overview...A mid/upper level ridge remains in place
Wednesday, then some influence from a Canadian upper-level
trough will push the ridge southward some Thursday and Friday.
At the surface, a warm front lifts northward Wednesday then a
trough arrives Thursday with a cold front approaching from the
northwest Friday.

Wednesday...Surface high should remain the dominant feature for
one more day, leading to one more day of tranquil conditions. As
the high shifts further off shore though, southwesterly flow
will develop, leading to increasing dewpoints, although,
guidance still shows the dew points in the lower 60s even late
on Wednesday, which is humid, but not oppressively humid.

Thursday (Independence Day) through Saturday...Southerly flow
becomes more established leading to hot and humid conditions all
three days (though Saturday is dependent on if a cold front will
stay northwest of our region. The influence of a Canadian
upper-level trough will start to approach during Thursday,
however the timing and amplitude of this trough is less certain.
As of now, the main trough is more toward the Midwest and
therefore a cold front may be slow to approach our area late in
the week. There may be a pre-frontal trough in our vicinity
Thursday into Friday and this may provide enough focus amid a
destabilizing air mass to initiate some convection.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Overnight...A weakening band of showers and embedded thunder
slides across the I-95 terminals with a time of MVFR or IFR
conditions. Otherwise, MVFR conditions develop late with some
low clouds and/or fog. Light southerly winds. Low confidence
overall.

Sunday...Low ceilings should gradually lift to VFR between 15
and 18Z. After 18Z (and likely closer and after 21Z), a round
of showers and storms affects the TAF sites. Winds should
gradually shift to southwesterly through the morning, remaining
around 10 to 15 kt. Moderate confidence.

Outlook...

Monday through Wednesday...VFR.

Thursday...MVFR possible with SHRA and TSRA especially in the
afternoon.

&&

.MARINE...
As of 1150 PM, cancelled the Small Craft Advisory for Delaware
Bay as conditions remain below criteria. The Small Craft
Advisory remains in effect through Sunday for the New Jersey and
Delaware Atlantic coastal waters, however did delay the
increase in winds and seas until during Sunday morning (after
daybreak) given lower conditions ongoing. Winds shift to the
northwest Sunday night behind a cold front.

Some showers and a thunderstorm overnight. VSBY restrictions in
fog through Sunday morning on the ocean waters. Showers and
thunderstorms will impact the waters Sunday afternoon and most
of Sunday night.

Outlook...

Monday through Thursday...Winds and seas should be below SCA
criteria.

Rip Currents...

Sunday...South-southwest winds around 15-20 mph with breaking
waves of 2-3 feet are expected. Swell periods are expected to a
bit longer than those of Saturday up to 6-7 seconds in length.
Due to winds around 15-20 mph and a longer swell period, have
opted to go with a MODERATE risk for the development of
dangerous rip currents for both the Jersey Shore and Delaware
Beaches on Sunday.

Monday...North-northeast winds around 10 mph with breaking waves
around 1-2 feet. As winds and breaking waves are much lower
compared to those on Sunday, have opted to go with a LOW risk
for rip currents for both the Jersey Shore and the Delaware
Beaches on Monday.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory from 11 AM to 7 PM EDT Sunday for PAZ070-071-102-
     104-106.
NJ...Heat Advisory from 11 AM to 7 PM EDT Sunday for NJZ010-012-013-
     015-017>020-027.
DE...Heat Advisory from 11 AM to 7 PM EDT Sunday for DEZ001.
MD...Heat Advisory from 10 AM to 7 PM EDT Sunday for MDZ012-015-019-
     020.
MARINE...Small Craft Advisory until 7 PM EDT Sunday for ANZ450>455.

&&

$$

SYNOPSIS...Gorse/Johnson
NEAR TERM...Gorse/MPS
SHORT TERM...Gorse/Johnson
LONG TERM...Gorse/Johnson
AVIATION...Gorse/Johnson
MARINE...DeSilva/Gorse/Johnson/MPS