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FXUS61 KPHI 011017
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
617 AM EDT Mon Jul 1 2024

.SYNOPSIS...
High pressure builds in later today through Tuesday before
moving offshore Wednesday. A more active period resumes Thursday
with the arrival of a surface trough but a cold front may not
push through the region until towards the end of this coming
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
A significant air mass change has occurred in the wake of a cold
front, therefore it will be much cooler with much lowered dew
points/humidity through tonight.

As of 615 AM, the cold front has cleared our entire area with
much cooler and drier air in place. Across our lower Delmarva
zones however, a few showers are still possible early this
morning mainly across eastern Sussex County, DE. Some clouds
hanging on across our far south and southeast zones, however
these are shifting eastward more now. In the northerly flow,
areas of stratocumulus are sliding south-southwestward across
our far northwest and western zones. Made some adjustments to
the sky grids to account for this better, and also tweaked the
hourly temperature and dew point grids based on the latest
observations and trends.

Otherwise, the axis of an upper-level trough is forecast to
cross our area through about early this afternoon. As this
occurs, the center of high pressure across the Great Lakes and
upper Ohio Valley gradually builds eastward. This will result in
a northerly wind today, and there is a tightened pressure
gradient across our area. This is the most pronounced through
about early afternoon, therefore with deeper mixing with heating
through the morning enhanced some by cold air advection, a
notable northerly breeze will be present today. This should
start to diminish some by later in the afternoon as the pressure
gradient starts to weaken as high pressure draws closer. Given
the colder air aloft, cyclonic flow for a while and the passage
of the trough axis, some stratocumulus is expected to be around.
The forecast soundings show enough moisture at the top of the
boundary layer to promote some of these clouds. Given the
presence of the trough axis crossing our area through early
afternoon, there could be a period of even more cloud cover
especially given a strengthening subsidence inversion through
the day. High temperatures are forecast to be below average for
this time of the year, and with dew points down into the 50s and
a breeze it will feel significantly cooler today.

Any stratocumulus dissipates into this evening as high pressure
continues to get closer and even drier air pushes in. The winds are
forecast to pretty much decouple in most places during the evening
into the overnight. This combined with a clear sky and a much drier
air mass will result in lows in the 50s late tonight for much of the
region (some lower 60s in the urban centers and along the
coast).

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
High pressure remains the name of the game during the short term
forecast period. This will continue a dry and overall pleasant start
to the new month across the region. Highs on Tuesday will be near
normal, mainly in the low-mid 80s. However, dew points forecast to
remain in the 50s. Additionally, the high looks to be centered
fairly directly over the region during this time period, leading to
light winds across most of the region outside of a sea breeze
potentially developing in the afternoon hours. All together, another
pleasant day looks to be on tap. Lows Tuesday night will be a touch
warmer compared to Monday night as well, mainly in the low-mid 60s.

The high will continue to progress eastward Tuesday night into
Wednesday and slide offshore. This will shift winds to be more
southerly, strengthen slightly, and begin to slowly draw more warm
and moist air back into the region. Wednesday looks to remain
pleasant overall though with highs mainly in the mid-upper 80s and
dew points in the upper 50s to near 60. Wednesday night lows are
forecast to fall into the mid 60s with upper 60s to near 70 in the
heart of the I-95 corridor.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
The forecast for the long term period is largely unchanged, an
increase in activity is still expected with decreasing influence
from high pressure as an upper-level trough across Canada suppresses
the upper-level ridge southward. Models continue to indicate the
formation of a secondary trough over the Midwest and potential slow
progression eastward.

With a series of shortwave impulses pushing through the region ahead
of the upper-level trough, chances for showers and thunderstorms
exist for each day of the long term period. Owing to a lack of
uncertainty in upper-level support, chances generally peak around 30-
40 percent right now and are focused on the afternoon and evening
hours of each day. What is looking more likely with this forecast
update, is the lack of relief from increasingly humid conditions
through the end of the week if the upper-level trough remains back
to the west. While high temperatures are forecast to remain steady
in the upper 80s to low 90s, dew points look to continue to increase
through the end of this week, potentially rising into the mid 70s.
Some relief may arrive by next Sunday but that will be highly
dependent on the amplitude of the upper-level trough and the
strength of the associated surface cold front.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...VFR. North-northwest winds 10-15 knots with gusts up to 25
knots, diminishing by later this afternoon. Moderate confidence.

Tonight...VFR. Northerly winds 5-10 knots, becoming light and
variable at many of the terminals. High confidence.

Outlook...

Tuesday and Wednesday...VFR with no significant weather.

Thursday and Friday...Sub-VFR conditions possible with chances (30-
40%) for SHRA and TSRA, especially in the afternoon and evening.

&&

.MARINE...
A northerly wind will be in place today and with cold air advection
occuring within a tightened pressure gradient, mixing is expected to
be sufficient for gusts of 25-30 knots. A northerly wind surge is
occurring on Delaware Bay early this morning. The winds should lower
some this afternoon as the pressure gradient starts to weaken and
mixing also decreases. Will maintain the Small Craft Advisory
through early this afternoon, otherwise the conditions are
anticipated to be below advisory criteria through tonight.

Outlook...

Tuesday through Friday...Conditions are forecast to be below Small
Craft Advisory criteria.

Rip Currents...

Today...Northerly winds 15-20 mph with gusts up to 30 mph will
gradually diminish some later this afternoon. Due to these elevated
winds and breaking waves of 2 to 3 feet, there is a MODERATE risk
for the development of dangerous rip currents for the Jersey Shore
and the Delaware Beaches.

Tuesday...Northeast to east winds near 10 mph with lower breaking
waves will result in a LOW risk for the development of dangerous
rip currents for the Jersey Shore and the Delaware Beaches.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 1 PM EDT this afternoon for ANZ430-
     431-450>455.

&&

$$

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