588
FXUS61 KPHI 180604
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
204 AM EDT Sat May 18 2024

.SYNOPSIS...
An area of low pressure slides to our south over the weekend.
High pressure then builds across our area early next week before
shifting to our south. A cold front then moves through Thursday
into Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure to our northeast nosing southwestward combined
with the coastal storm now fairly far off the coast continues to
result in marine influence across our region. Thus, despite
approaching shortwave trough, overall forcing for showers will
be dwindling as the system moves into and then crosses the
region through today into this evening. Shower chances will be
highest to the west and southwest of our region, across interior
eastern PA and down across the Delmarva, closer to the edge of
the marine influence where temps are warmer and more instability
is to be had. That said, not expecting any thunder today as its
just not enough to produce strong convection. All that having
been said, still looks mostly dry this morning, but with plenty
of clouds, and shower chances are highest overall across the
region this afternoon as the best upper forcing moves in aloft.
With all the clouds around, temps won`t be very warm, but not
much different from what much of the region experienced
yesterday... upper 60s with a few 70s. Today, however, best
chance of 70s will be in interior central and northern New
Jersey, where precip likely takes longest to reach (if it does
at all).

As our upper forcing heads east out to sea overnight tonight,
shower chances end, and while we don`t expect much clearing
overnight as the winds just don`t provide any push of drier air
behind the upper trough, any breaks could help some patchy fog
develop, especially where rain falls today. Right now, the best
odds appear to be northwest of I-95 across the Lehigh Valley and
Poconos, though also parts of the Maryland eastern shore. Lows
mostly in the 50s.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Surface high pressure extends southward into our area Sunday,
with most of the energy now confined to the south of the area
which will help to completely end the shower chances. Some
lingering low-level moisture though and especially if the clouds
clear enough may result in patchy fog early Sunday. By Sunday
afternoon, expect at least some sunshine to make a return. High
temperatures top out into the 70s for many inland areas,
although a lingering onshore flow will keep it much cooler
closer to the coast.

As an upper-level ridge starts to build over the area Monday,
surface high pressure becomes more centered across our region.
The increasing subsidence and drier air should assist in less
cloud cover for much if not all of the region. The air mass will
continue to modify and therefore afternoon high temperatures
are forecast into the 70s again for much of the area. A
northeast wind though should turn east to southeast as a sea
breeze becomes more established and this will yet again keep it
much cooler closer to the coast Monday.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Summary...Above average temperatures and dry to start, followed
by some chances for showers/thunderstorms with a cold front.
Some cooling then possible Friday.

Synoptic Overview...An upper-level ridge is forecast to be
across much of the East Tuesday before it shifts offshore
Wednesday. An upper-level trough tracking eastward from south-
central Canada to the mid-Mississippi Valley will drive surface
low pressure well to our north. A cold front however is forecast
to arrive across our area Thursday into Friday as the upper-
level trough mostly glances the Northeast. The flow aloft then
may turn more zonal into Friday, although a shortwave trough in
the Tennessee Valley may make a run at our area later Friday.
The latter is much more uncertain at this time range.

For Tuesday and Wednesday...Given the presence of upper-level
ridging overhead Tuesday along with high pressure at the
surface, a warmer air mass will be in place. The light winds
however should result in a sea breeze Tuesday afternoon which
will then make a run inland keeping it cooler closer to the
coast. This setup is expected to result in no precipitation and
a decent amount of sunshine given the subsidence. As we go
through Wednesday, more of a return flow should become
established as the ridge aloft and also the surface high shifts
offshore. Low-level warm air advection should increase some with
this southerly flow ahead of an upper-level trough which drives
surface low pressure and a cold front. The forward
motion/timing of the cold front is less certain especially as
the main upper-level trough may just glance the Northeast and
the surface low tracks well to our north. It is possible a band
or broken band of showers and thunder makes it into our far
western zones late Wednesday tied to a surface trough. Given the
initial subsidence and favorable setup, temperatures were
bumped up some especially away from the coast.

For Thursday and Friday...The aforementioned upper-level trough
glances our area Thursday however a cold front tied to low
pressure well to our north should move through sometime during
this time frame. There looks to be enough forcing to produce
some showers and instability should be sufficient during the
afternoon and evening Thursday for some possible thunderstorms.
The warmth (and more humid) may peak Thursday ahead of the cold
front with widespread low to mid 80s for highs, although
probably cooler closest to the coast due to a southerly wind. As
of now, the cold front should be offshore to start Friday with
some cooling in its wake. The cooling does not look all that
significant at this time given the weakness of the upper-level
trough and it tending to just glance our region.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Through Today...Genearlly VFR early this morning. Approaching
showers and continued easterly to northeasterly flow will result
in cigs dropping to MVFR most terminals by midday. Vsby may
briefly drop to MVFR but mostly VFR vsby expected despite
passing shwoers. Winds fairly light and variable at times but
overall, a weak easterly flow will prevail. Moderate confidence.

Tonight...scattered showers end but MVFR cigs linger. May be
some patchy fog to reduce vsby esp NW of I-95 terminals.
Continued light/variable flow with a general easterly
persuasion. Low confidence.

Outlook...

Sunday...Areas of MVFR conditions possible with lingering
showers Saturday evening, then VFR overall.

Monday through Wednesday...VFR overall.

&&

.MARINE...
Ocean wave heights may flirt with 5 feet early this morning but
should generally subside thereafter, so no plans for a Small
Craft Advisory at present. Otherwise, northeasterly winds will
prevail through tonight with speeds of 5-10 kts today increasing
slightly to 10-15 kts tonight.

Outlook...

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

.Rip Currents...

Winds are generally around 5 to 10 mph, and the rip current risk
is no longer HIGH. Will therefore cancel the HIGH risk for rip
currents that was set to expire at 8 pm.

A prolonged period of N to NE winds at 5 to 10 mph through the
weekend along with 3 to 4 ft seas will result in a MODERATE risk
for the development of dangerous and life threatening rip
currents on Saturday and Sunday.

&&

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

&&

$$

SYNOPSIS...RCM
NEAR TERM...RCM
SHORT TERM...Gorse/RCM
LONG TERM...Gorse
AVIATION...Gorse/MJL/OHara/RCM
MARINE...Gorse/MPS/OHara/RCM