077
FXUS61 KPHI 210550
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
150 AM EDT Tue May 21 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 TODAY/...
Forecast running on track. No changes will be made to the
database other than to adjust hourly grids based on latest
surface obs.

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

Early this morning (through 12Z)...VFR to start for most, but
marine fog is forecast to advect inland later this morning,
leading to areas of mist and fog. A few sites have already seen
moments of IFR or lower at times during the overnight period.
IFR CIGs/VSBYs become more prevalent at KACY/KMIV after 08-10Z.
MVFR CIGs/VSBY will become more prevailing across the I-95
terminals with moments of IFR possible. KABE/KRDG will likely
remain in VFR/MVFR. Moderate confidence overall, but lower with
respect to timing of CIGs/VSBY reductions.

Tuesday...Any IFR/MVFR CIGs should rise to VFR by 14-16Z 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...

Winds become S from 5 to 15 mph on Tuesday. Winds in northern
NJ will be closer to 10 to 15 mph, and winds at coastal DE will
be a bit more offshore. For beaches in Monmouth, Ocean,
southeast Burlington counties, as well as Delaware beaches,
there is a MODERATE risk for the development of dangerous and
life threatening rip currents. For southern NJ, winds will be a
bit lighter, generally 5 to 10 mph. As a result, there is a LOW
risk for the development of dangerous and life threatening rip
currents for beaches in Atlantic and Cape May counties.

There will be a Full Moon on May 23. S winds will range from 10
to 15 mph with gusts up to 20 mph. As a result, there is a
MODERATE risk for the development of dangerous and lift
threatening rip currents at NJ and DE beaches on Wednesday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Dense Fog Advisory until 4 AM EDT early this morning for
     ANZ430-431.

&&

$$

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