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000
FXUS61 KPHI 170825
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
425 AM EDT Wed Apr 17 2024

.SYNOPSIS...
High pressure continues to move offshore as a series of fronts and
low pressure systems begin to affect the East Coast today through
the end of the week. High pressure looks to return for the weekend
and the start of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A ridge of high pressure centered just offshore will continue to
gradually shift to the east through today as a cutoff low shifts
north over the Great Lakes. Its warm front will get a little closer
to our area during the course of the day with a period of stronger
warm air advection. A fairly narrow corridor of showers looks to
accompany the isentropic lift, which should begin affecting the I-95
corridor from Wilmington to Philly around midday or so as it moves
in from the west. Showers will therefore be on the increase
especially in the afternoon as these showers continue moving east. A
cool onshore flow will help keep an inversion in place for much of
the day, limiting any instability and, therefore, limiting
thunderstorm development during the afternoon hours. High
temperatures should range from around 55 to 60 over the southern
Poconos into NW NJ, as well as right along the shore, to the mid to
upper 60s over SE PA into interior portions of southern NJ and
Delmarva.

Overnight tonight, the initial upper level low over the Great Lakes
will "open up" as a piece of its energy splits off from this and
moves towards the region. This will keep some off and on showers
going over the area tonight and it`s also possible there could be
some rumbles of thunder due to a small amount of elevated
instability. At the surface, a triple point will move eastward from
near West Virginia through Delmarva and then off the coast by around
12z Thursday. Expect overnight lows are expected to range from the
mid to upper 40s over NE PA into northern NJ to the 50s over SE PA,
southern NJ, and Delmarva.

Heading into the day Thursday, weak low pressure develops off the
coast associated with the de-amplifying upper level wave that was
once the cut-off low. This will help winds back from easterly to
more northeasterly helping drag a backdoor cold front southward into
the region. The result of this is it will be a generally cooler day
for most under continuing mostly cloudy skies with some lingering
showers and drizzle, especially during the first half of the day and
over NE PA into northern NJ. Highs over the southern Poconos into NW
NJ may only get to around 50 or so while SE PA into southern NJ
should see highs around 60 and parts of Delmarva may still get to
the upper 60s to around 70.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Overall, the short term forecast remains largely unchanged. By
Thursday night, the weak coastal low will be shunted southward
enough that surface high pressure can build in and briefly shutoff
the chances for showers. Lows Thursday night look to fall into the
40s most everywhere across the region.

Following the brief respite from showers Thursday night, the next
mid-level wave approaches the region on Friday. Latest guidance
continues to indicate that the pre-existing high will be strong
enough to hold off any precipitation through the morning. However,
the approaching wave will eventually move in and bring yet another
cold front across the region with the opportunity for more showers.
Chances for showers begin to increase Friday afternoon and look to
peak Friday night. However, the front overall looks to be drier than
previously forecast so chances for precip Friday night are now
around 30-40 percent at most. Showers look to clear the region by
late Friday night/early Saturday morning. Temperatures will rise
into the upper 50s to low 60s during the on Friday before falling
into the upper 40s to low 50s Friday night.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
An overall nice weekend now looks to be on tap with high
pressure beginning to take over on Saturday with the front from
Friday stalling to the south of the region. Long range guidance
is continuing to suggest that a system will slide by just to our
south on Sunday or Monday along the boundary. Depending on
exactly how far south the front stalls, this would potentially
allow a few showers to leak back into the most southern portion
of the region Sunday night but this remains highly uncertain.
With the front to the south of the region though, temperatures
will likely be below normal through the long term with highs in
the upper 50s to mid 60s and lows in the upper 30s to low 40s.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Through today...VFR ceilings lower to MVFR during the late afternoon
(after 20z). Some showers develop as well, however these should be
lighter in intensity. Light and variable winds early this morning
becoming east-southeast 5-10 knots. Moderate confidence overall.

Tonight...Lows stratus and showers linger with MVFR cigs likely
dropping to IFR by the overnight time period. Visbys should get down
to at least MVFR and possible IFR as well due to some mist/fog. East
winds 5 to 10 knots backing to northeast through the overnight.

Outlook...

Thursday night through Sunday...VFR overall, however a brief period
of sub-VFR is possible (30 percent) Friday night through Saturday
morning.

&&

.MARINE...
Winds and seas remain tranquil through today at sub Small Craft
Advisory levels. They should then start to increase tonight with SCA
conditions likely developing Thursday as a backdoor cold front works
southward over the waters. These conditions should develop north to
south with it being more marginal farther south. In fact it may stay
sub SCA off the coast of Delaware.

Outlook...

Thursday Night...Small Craft Advisory in effect for New Jersey
Atlantic Ocean coastal waters due to expected seas of 5-7 feet.
Gusts up to 25 knots are also possible, particularly for coastal
waters north of Little Egg Inlet. SCA conditions also possible
(25-35%) for Atlantic Ocean coastal waters south of Cape May
due to 5 foot seas.

Friday...SCA conditions possible (40-50%) due to lingering 5 foot
seas.

Friday night through Sunday...Slight chance (15-25%) for SCA
conditions Saturday afternoon and evening due to winds, otherwise,
sub-SCA conditions.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 6 AM Thursday to 6 AM EDT Friday for
     ANZ450-451.
     Small Craft Advisory from 6 PM Thursday to 6 AM EDT Friday for
     ANZ452>454.

&&

$$

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