-- Discussion containing changed information from previous version are highlighted. --
103
FXUS61 KPHI 141046
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
646 AM EDT Fri Jun 14 2024

.SYNOPSIS...
A cold front approaches today and crosses through late
afternoon into tonight. High pressure begins to build later
tonight and holds a dominate grasp over the region through the
weekend. A warm front lifts through Monday, but more surface
high pressure looks to control the region through at least the
middle of week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Friday will start off rather tranquil before a round of
thunderstorms arrive for the second half of the day. An upper-level
trough is forecast to arrive later today, bringing with it a cold
front that will push through from west to east this afternoon and
evening. While the parent trough is farther north, the southern
portion of it has stronger shortwave energy and is timed during peak
heating across our region. Ample instability is forecast to be in
place (MUCAPE up to 1500 J/Kg) given air temperatures forecast to be
in the 80s with even some lower 90s and dew points in the 60s. The
model forecast soundings show a well mixed and warm boundary layer
in the afternoon and early evening. This results in an inverted-V
profile in the lower levels and thus increasing the downdraft
instability (DCAPE). Low-level lapse rates are rather favorable as
well, with around 9.0 C/km in the 0-3km layer, moderating to around
6.0 C/km in the 3-6km layer. This all said, the limiting factor is
expected to be deep layer shear, with rather weak flow in the low
and mid levels and stronger winds in the upper levels. The best
shear is also displaced north and west of the region with only about
30-40kt of deep layer shear in place ahead of the frontal passage.

Putting this all together, convection is forecast to develop to our
northwest and west and then propagate east and southeastward during
the afternoon and evening along and ahead of the cold front. While
coverage and timing does vary some among the guidance suite,
convection should organize into a few clusters or a broken line as
it shifts into and across our area, with this possibly weakening
near and especially south and east of I-95. This will depend on the
timing as southerly flow ahead of the convection and front will
bring some marine influence into portions of the coastal plain.
Locally damaging winds are the main severe weather threat especially
with stronger cores aloft (along with some mid level dry air)
enhancing the downdraft/downburst potential. Freezing levels look to
be on the higher side, however some hail cannot be ruled out with
some stronger updrafts. The precipitable water values are forecast
to be approaching 2 inches for a time ahead of the cold front, and
therefore high rainfall rates should occur with the strongest
convection for a time. The flash flooding risk however looks to be
low overall as storms should be on the move, however there is a non-
zero risk focused across mostly our northern and western zones. SPC
maintains a Slight Risk for severe weather for areas north and west
of the I-95 corridor and a Marginal Risk elsewhere.

The convection looks to be shifting offshore or weakening during the
evening hours with the severe thunderstorm risk ending. Some drier
air then starts to arrive from the northwest in the wake of the cold
front by later Friday night with at least some partial clearing also
starting to arrive. Overnight lows will cool into the upper 50s to
mid 60s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Surface high pressure will dominate over the region for the duration
of the short term; a dry and quiet forecast is on tap for the
weekend.

Not much to write home about regarding this forecast! Highs mainly
in the low to mid 80s for Saturday; highs just a bit warmer for
Sunday, by about 1-2 degrees. Very comfortable RHs expected for
both days with plenty of sunshine. Overall, a stellar weekend!

A sea-breeze will likely develop on Sunday given the weak synoptic
flow in the forecast. This sea-breeze could penetrate well in-land
by the late afternoon into evening hours.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Summary...Hot but mainly dry forecast.

The synoptic pattern and evolution is nearly certain for the long
term. An upper-level ridge over the eastern CONUS Monday will build
to the north with time. By the Wednesday time frame, the strong
ridge will look to be centered directly over the northeastern CONUS
and will likely stay in place for quite a bit. The ensembles suggest
it is not until around the time frame of Friday that the ridge and
its associated axis will begin to break down a bit.

Overall, heights will only build over the region with time Monday
onwards. We could see heights of 594-600 dam over us for Wednesday.
At the surface level, high pressure centered offshore Monday will
move eastward with time as a warm front lifts over the region. Even
still, surface high pressure looks to largely control the region
through the duration of the term. Though some rounds of shortwave
energy may pester the region for much of the week, any precipitation
development should be largely suppressed given the pattern.

We are mainly looking at a dry forecast into Thursday with
temperatures potentially getting warming each day. High
temperatures may touch the low 90s for Monday, but widespread
highs in the 90s should be anticipated at this point for
Tuesday, Wednesday, and Thursday. It is still a little too early
to really discuss any potential for heat headlines at this
point, but the potential will only grow with time as the week
progresses.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Friday...VFR for much of the time, however sub-VFR conditions
possible later in the afternoon and evening as showers and
thunderstorms move through with a cold front. South to southwest
winds around 10 knots, becoming west later in the afternoon at
KRDG and KABE. Brief restrictions likely as the line of
showers/thunderstorms move through. Some storms could result in
variable, gusty winds as well. TEMPO groups added this update
to reflect the risk of sub-VFR visibilities from heavy rain and
gusty winds from strong thunderstorms. Moderate confidence in
impacts from storms. Low confidence in timing.

Friday Night...Restrictions likely (60-70%) as a cold front moves
through. Some showers possible behind the initial line of
showers/thunderstorms. Westerly winds will become more northerly
with the frontal passage, around 5-10 kt. Low confidence.

Outlook...

Saturday through Tuesday...VFR with no significant weather.
-- End Changed Discussion --

&&

.MARINE...
Through Friday, the conditions are anticipated to remain below Small
Craft Advisory criteria. Southerly winds should be the strongest at
times across the northern New Jersey coastal waters and possibly up
Delaware Bay. However, given much warmer air moving over the cooler
waters, mixing should be more limited and since it looks marginal
opted to keep the conditions below advisory criteria. Some showers
and thunderstorms should arrive late Friday afternoon and Friday
night, and some storms could produce locally gusty winds. Winds turn
more northerly around 10 kts Friday night behind the frontal
passage. Seas linger around 2-4 feet.

Outlook...

Saturday through Tuesday...No marine headlines expected. Fair
weather.

Rip Currents...
On Friday, south winds increase to around 15 mph with 20 to 25
mph gusts. The flow will be a bit more onshore for most of New
Jersey as opposed to Delaware. Additionally, guidance shows a 2
ft 9-10 second longer period swell from the SE to SSE developing
by the afternoon. As a result, there is a MODERATE risk for the
development of dangerous rip currents for New Jersey beaches
where the coastline is more perpendicular or oblique to the
longer period swell. LOW risk for the development of dangerous
rip currents for the Delaware beaches. Breaking waves will be
around 2 to 3 feet.

Winds turn offshore for Saturday, with a LOW risk for rip
currents everywhere.

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

&&

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

&&

$$

SYNOPSIS...Wunderlin
NEAR TERM...Gorse/Hoeflich/MJL
SHORT TERM...Wunderlin
LONG TERM...Wunderlin
AVIATION...AKL/Gorse/Hoeflich/MJL/Wunderlin
MARINE...AKL/Gorse/Hoeflich/Wunderlin