645
FXUS61 KPHI 152352
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
752 PM EDT Sat Jun 15 2024

.SYNOPSIS...
High pressure builds across our area tonight then shifts offshore of
New England during Sunday. As this high becomes situated to our east
all of next week, a warm front lifts across our area Monday.
Building high pressure aloft all of next week will result in a
prolonged stretch of hot conditions with little to no rain
chances.

&&

.NEAR TERM /THROUGH SUNDAY/...
1025 mb high pressure centered over Lake Huron this evening
will track across the Northeast tonight and off the New England
coast Sunday. Wind flow around the high will result in a
northerly flow through tonight, except for onshore seabreezes at
the coastline. Winds become east to southeasterly on Sunday.
The high and associated subsidence will keep the sky mainly
clear through Sunday.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
Building heat and humidity, especially on Tuesday.

As a ridge aloft builds across the Southeast U.S. Sunday night into
Monday, surface high pressure works its way farther off the New
England coast. This ridge is also forecast to expand northward
through Tuesday. A warm front should lift across our area during
Monday with warm air advection on the increase. The cooler air mass
hangs on Sunday night before turning much warmer and a little more
humid during Monday. The warm front may be accompanied by some
clouds, however limited moisture and not much forcing with the
building ridge in place is expected to keep it precipitation-free.

As we go through Monday and Tuesday, the heat will be on as heights
rise and therefore so do the temperatures aloft and at the surface.
A more southerly flow commences on the backside of surface high
pressure and while this is not all that strong it will result in
some cooler temperatures closer to the coast. This should be enhanced
some by a sea/bay breeze. Temperatures Monday are forecast to be into
the 80s across much of the region, with even some places getting to
90 degrees especially in the I-95 urban corridor. The dew points
should lower some during peak heating and therefore it should not be
all that humid. Even hotter conditions settle in for Tuesday as the
ridge builds with some increased subsidence and thus warming aloft.
Nearly all areas away from the coast should get into the 90s and
with higher dew points (mid to upper 60s) the heat indices are
forecast to peak right near 100 degrees from about the I-95 corridor
to the north and west. If the dew points remain high enough Tuesday
night, many places may only have temperatures drop to near 70
degrees and therefore a much warmer and muggy night. Some record
high temperatures could be challenged Tuesday afternoon. More below
regarding the run of excessive heat.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Summary...Excessive heat probable with little to no rain chances.

Synoptic Overview...A mid to upper level ridge is forecast to be
centered over our area into Friday, however thereafter it may start
to weaken and shift southward some. This maintains surface high
pressure centered offshore although it does extend into our area
before shifting southeast Friday into Saturday.

For Wednesday through Saturday...The upper air pattern that is
forecast continues to point toward an extended period of heat across
much of the area (high temperatures 90F+ degrees). An expansive and
deep ridge is forecast to be centered across our region with some
additional warming occurring aloft through Friday. The 850 mb
temperature forecasts vary some among the model guidance, ranging
roughly from +16C to +22C across our region, and this will have some
impact on the surface air temperatures. The latter half of the week
as of now look to be the hottest. The heat dome will maintain
surface high pressure to our east with the surface flow more out of
the south. This looks light and the moisture advection is not much,
and therefore surface dew points should not be crazy with this heat.
In addition, many days of hot temperatures tends to lower the dew
points some during peaking and this can be enhanced some by a dry to
drying ground. There will also not he much relief at night
especially in the urban corridor with lows dropping only into the
70s. The southerly flow however should keep the coastal areas
noticeably cooler than inland, and if the flow is light enough
especially under this ridge then a sea breeze many days could get
farther inland during the later afternoon hours. The ridge also
tends to limit cloud development and therefore rain especially given
warm air aloft. As a result, convective chances are little to none.

The guidance overall showing the strong ridge starts to get pushed
southward some and elongates more west to east Friday into Saturday
as a trough in south-central Canada starts to flatten the northern
side of the ridge. A Heat Advisory looks probable for many areas
during this stretch as dew points should be low enough to keep heat
indices below warning criteria, however the multi-day heat tends to
have more impacts especially in urban centers when combined with
less relief at night. Given the potential impacts of this heat, an
Excessive Heat Watch was considered for much of the area especially
for the urban corridor from Wilmington to Philadelphia to Trenton
and the immediate surrounding zones. Given the main heat starting
Tuesday and collaborating with our neighboring offices, opted to
hold off on a Watch. We will go ahead though and issue briefings to
our core partners. Also to note is the NWS Heat Risk graphics which
show moderate to some areas of major heat-related impacts for much
of our area.

The ridge should be flattening some on the north side Saturday which
lowers the heights some and also the temperatures aloft. However
despite this, the heat looks to certainly continue. There may also
be some opportunity for a few showers or thunderstorms especially
for our northern zones which will be closer to the Canadian trough.
Given the presence of the ridge though, PoPs are only in the 20-30
percent range mainly across the northern into the central parts of
the region at this point.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight...VFR. NNW winds around 5-10 knots early this evening
except at KMIV/KACY where a seabreeze has turned winds to be out
of the S. Winds then become N to NNE at less than 5 knots. High
confidence.

Sunday...VFR. East to Southeast winds increasing from around 5
knots early to around 10 knots in the afternoon. High
confidence.

Outlook...

Sunday night through Thursday...VFR with no significant weather
impacts anticipated.

&&

.MARINE...
No headlines expected. N winds 10-15 kts this afternoon,
becoming light and variable overnight. East to southeast winds
10 to 15 knots Sunday. Seas 2-4 feet.

Outlook...

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

Rip Currents...

With lighter winds around 10 mph and lower waves of 1-2 feet on
Sunday, there will be a LOW risk for the development of
dangerous rip currents for both the New Jersey Shore and
Delaware Beaches.

On Monday, winds will increase back to 10-15 mph but look to be
out of the south. This wind direction would result in largely
shore parallel winds except for the more south facing beaches in
Cape May and Atlantic Counties. Additionally, waves in the surf
zone are forecast to remain 1-2 feet with a short-medium period
swell. Combining all these factors together, we are forecasting
a LOW risk for the development of rip currents on Monday for
now.

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

&&

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

&&

$$

SYNOPSIS...Gorse
NEAR TERM...AKL/Franklin/MJL
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...AKL/Franklin/Gorse/MJL
MARINE...AKL/Franklin/Gorse/MJL