535
FXUS61 KPHI 201941
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
341 PM EDT Mon May 20 2024

.SYNOPSIS...
A weak area of high pressure over our area will gradually settle to
our south and east Tuesday. A cold front crosses our region Thursday
afternoon or evening, then it stalls to our south through the
holiday weekend. As high pressure slides across New England Friday
through Saturday, weak low pressure may track near Delmarva. Another
low pressure system is forecast to track across the Ohio Valley to
near the eastern Great Lakes Sunday into Monday.

&&

.NEAR TERM /THROUGH TUESDAY/...
High pressure located over southern New England is causing tranquil
weather across the area this afternoon. Visible satellite imagery
continues to show the eroding marine layer from this morning, which
has given way to sunny skies with the exception of the northern
Delmarva where more clouds than sun persist. Temps are in the mid
70s and lower 80s.

Heading into tonight, the surface high will move overhead before
ultimately settling to our south on Tuesday. Overall, not expecting
too much change for the first portion of the night other than winds
gradually becoming more southerly. However, hi-res guidance
continues to indicate another round of low stratus moving onshore
and overspreading the area early Tuesday morning. Not anticipating
as strong of a push as this morning due to southerly flow, but
general thinking is there will be areas of mist and fog, more so
across the immediate coastal plain. Lows mostly in the mid 50s to
around 60 degrees.

For Tuesday, any morning fog and/or stratus will quickly lift and
dissipate by mid-morning. This will give way to clear skies during
the afternoon with just some spotty diurnal cumulus. Another dry and
quiet weather day is expected. High temps should be a bit warmer
than those of today, rising into the upper 70s to mid 80s. Temps
will be noticeably cooler along/near the shore thanks to light
surface winds allowing an afternoon sea breeze circulation to
develop.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
Warmth continues and turning more humid ahead of a cold front.

As a ridge sits to our east and south, surface high pressure will
also be centered near and offshore of the Carolinas. This will
continue to circulate warmer air into our area. A strong upper-level
trough is forecast to be tracking across the Midwest Wednesday
before lifting into adjacent Canada Wednesday night and Thursday.
Tuesday night and most of Wednesday is therefore expected to be dry
across our area, with a continuation of building warmth. The flow
looks to be southerly enough Wednesday to keep it cooler along the
coast. Some weakening convection from the west could make a run at
our western zones Wednesday evening before dissipating.

As the parent upper-level trough remains into Canada Thursday,
surface low pressure will be tied to it and track well to our north.
An associated cold front however will move across our area Thursday
afternoon or Thursday night. Prior to the cold front arriving, a pre-
frontal trough may become established just to our west and then
shift eastward during the peak heating Thursday afternoon. While the
main forcing is removed from our area given the main trough aloft is
so far to our north, a band of stronger southwesterly flow in the
mid levels is forecast to arrive during the day Thursday. The model
guidance overall shows ample instability with some increase in shear
due to the strengthening mid level southwesterly flow. The model
forecast soundings from the GFS and NAM show an inverted-V profile
in the lower levels given ample heating of the boundary layer.
Despite generally weaker forcing, a band or broken band of
convection may accompany the pre-frontal trough well ahead of the
cold front Thursday afternoon. Given the forecast environment, may
have to watch for locally strong winds with any more organized line
segments. The convection should be weakening or moving offshore
Thursday night as the cold front moves through.

High temperatures both Wednesday and Thursday are forecast to be
well into the 80s for much of the area (coolest along the coast and
higher elevations of the Poconos). Dew points are forecast to rise
into the 60s, with the highest values on Thursday ahead of the cold
front.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Summary...Some cooling through the holiday weekend although high
temperatures at or above average. Some showers are possible
especially Sunday and Monday.

Synoptic Overview...A more zonal flow aloft Friday as an upper-level
trough passes by well to the north, then a weak shortwave trough may
slide by as a ridge slides across parts of eastern Canada Saturday
into Sunday. Another upper-level trough may lift across the Great
Lakes and adjacent Canada Sunday into Monday. At the surface, a
front is forecast to be stalled to our south for the holiday
weekend. A few ripples of energy may slide across our nearby with
some weak surface lows also tracking up the Ohio Valley to near the
Great Lakes. High pressure initially sliding across New England into
Canada should extended into our area for a time.

For Friday and Saturday...As an upper-level trough glances our
region to the north Friday, surface low pressure is well to our
north. An associated cold front however should be stalling to our
east and south. There is limited cold air advection in the wake of
this cold front, and while temperatures will be cooler Friday they
are forecast to remain above average. The flow looks light and
therefore a sea breeze should develop and thus keeping it cooler
along the coast. The front remains to our south Saturday as well and
high pressure builds across portions of eastern Canada and extends
down across New England. This will turn our low-level flow to
onshore resulting in some cooling. This will be most notable closer
to the coast. Some showers and perhaps thunder will be possible
especially across our southern zones as a weak shortwave trough may
arrive later Friday into Saturday.

For Sunday and Monday...As the aforementioned shortwave trough
departs to the east to start Sunday, surface high pressure may
remain extended southwestward across much of our area. This will
maintain an onshore wind. While some showers will be possible during
both days, there may be a greater chance during Monday. This is less
certain though as it will depend on the timing and strength of an
upper-level trough shifting eastward from the Ohio Valley region.
Given the uncertainty, kept PoPs no higher than the chance range
which is similar to the NBM guidance.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Rest of Today...VFR with mostly clear skies. South-southeast
winds around 5-8 kt. High confidence.

Tonight...VFR for most of the night lowering to MVFR/IFR CIGs/VSBYs
after 04-06Z at KACY/KMIV and after 08-10Z for remainder of
terminals. Areas of patchy fog and mist are possible. Light south
winds around 5 kt becoming light and variable at times. Moderate
confidence overall, but lower with respect to timing.

Tuesday...Any IFR/MVFR CIGs should rise to VFR by 14-15Z at all
terminals. Mostly clear skies during the afternoon. South-southwest
winds around 5-10 kt. High confidence.

Outlook...

Tuesday night and Wednesday...Local fog possible early Wednesday
morning, otherwise VFR.

Thursday...Locally fog possible early, otherwise areas of sub-VFR
possible with some showers and thunderstorms mainly in the afternoon
and evening.

Friday...Mainly VFR.

Saturday...Some MVFR possible along with a chance of showers.

&&

.MARINE...
No marine headlines are in effect through Tuesday. South-southeast
winds around 10-15 kt with occasional gusts up to 20 kt. Seas around
3-4 feet. Patchy dense marine fog possible late tonight into Tuesday
morning.

Outlook...

Tuesday night through Saturday...The conditions are anticipated to
be below Small Craft Advisory criteria. Some locally gusty
thunderstorms possible later Thursday afternoon and evening.

Rip Currents...

A prolonged period of NE to E winds at 10 to 15 mph during the
day and 5 to 10 mph at night will continue. Along with 3 to 4
ft seas, this will result in a MODERATE risk for the development
of dangerous and life threatening rip currents today at New
Jersey and Delaware beaches. The rip current risk may be low for
most of the day for southern New Jersey beaches.

By Tuesday, the winds will be veering to more of a southerly
direction at 10 to 15 mph which will reduce the onshore
component at most beaches. However we`ll also be heading closer
to the Full Moon on the 23rd so for this reason expect that most
of our beaches will continue to see a MODERATE risk for the
development of dangerous rip currents.

&&

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

&&

$$

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