646
FXUS61 KPHI 212255
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
655 PM EDT Fri Jun 21 2024

.SYNOPSIS...
Bermuda high pressure remains in control through much of the weekend.
A front is forecast to remain just to our north through Sunday,
however a stronger cold front will then cross our area Monday.
High pressure returns for Tuesday followed by another front for
the middle of next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 650 PM, no significant changes needed to the forecast
with this update. A few showers and thunderstorms are sliding
east- southeastward from northeast Pennsylvania into far
northern New Jersey. An earlier stronger storm in Sussex County,
NJ produced small hail and a wind gust of 30-40 mph and locally
heavy rain. The downdraft instability (DCAPE) is stronger south
of the ongoing convection, however the more organized
convection should be to our northeast. The convection is
expected to wane through the evening as the boundary layer
gradually cools after sunset.

Otherwise, a front north of the region will remain there through
Saturday. Warm air advection will continue for the region as
will shortwave energy looking to propagate through.

Some showers and thunderstorms are expected this evening for
the northern and northwestern parts of our region. Some
thunderstorms that do develop could produce stronger downbursts
which could lead to localized damaging wind gusts. The SPC
maintains the MARGINAL risk for these areas. In addition, with
weak flow aloft, any showers and thunderstorms that do develop
will be relatively slow moving. A quick inch or two of rainfall
in some spots cannot be ruled out. WPC maintains some of our
northern and northwestern most areas in a MARGINAL risk for
excessive rainfall.

Very warm and muggy night on tap for tonight with lows primarily in
the low to mid 70s. Patchy fog is possible overnight mainly
where some rain occurs this evening.

For Saturday, the forecast high temperatures have come down
just a bit but overall the pattern/situation remains the same.
With confidence growing as we get closer to the day and
temperatures having come down just a bit, opted to replace the
Excessive Heat Watch in place for the I-95 corridor with a Heat
Advisory; no other changes made besides that. The I-95 sites
will likely see the mid to upper 90s as highs, but heat indices
will likely stay in advisory criteria. Basically, the same
shower and thunderstorm situation seen for today will repeat for
Saturday afternoon into Saturday night.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
The heat wave will continue into the short term, then some break in
the heat Monday following a cold front which moves through. The heat
headline, excessive heat watch, for Sunday will continue with highs
in the mid 90s widespread and some chance for upper 90s for the
urban areas. Heat index values in the 100-105 range expected for
Sunday. These temps will continue with high humidity too as deep
SW/S flow continues over the region. These remains some uncertainty
with regards to how much cloud cover and how fast it arrives. The
high temperature forecast may be affected by these factors.

More certainty is seen with regards to the precipitation forecast
as a front cuts through the heat and humidity creating good chances
for tstms Sunday/Sunday night. We will carry high chance and low
likely pops for the periods and continue with gusty winds/heavy
rainfall wording for now. The front moves offshore by Monday with
some lingering clouds/showers for NJ into Monday before improvement
from W to E Monday afternoon. High temps Monday will be in the mid
80s for the N/W areas and low 90s for srn NJ and Delmarva. Humidity
levels will decrease with a drier W/NW flow becoming established
over the area.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The upper high/ridge that has brought all the excessive heat to the
area this week and into the weekend will slowly lose its grip over
the northern Middle Atlantic region by early next week. Instead, we
will be closer to the westerlies (storm track) with the big high to
the SW and a weak mean trough across the Northeast. This means that
while we will still have the opportunity for a hot day (especially
Wed.) but we won`t be in another prolonged period of excessive
heat/humidity. Highs will largely favor the mid/upper 80s with a few
low 90s in the urban areas.

After the showers in the short term, the precipitation for the long
term will basically center on Wed./Wed night when a cold front and
upper trough cross the region. We will go with the 30-40ish (%) pops
offered by the NBM for now.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR. South to southwest winds 5-10 knots, becoming
locally light and variable at some terminals. Moderate
confidence.

Saturday...VFR, however some afternoon showers and thunderstorms
will be possible especially from near KTTN, KABE and KRDG.
Southwest winds increasing to near 10 knots, becoming south in
the afternoon mainly at KILG and KACY due to bay/sea breezes.
Moderate confidence.

Outlook...
Saturday night through Sunday night...VFR except in sct
showers/tstms when lower CIGS/VSBYS expected.

Monday...Morning lower clouds possible then VFR.

Tuesday...VFR.

Wednesday...Lower CIGS/VSBYS with scattered showers/tstms.

&&

.MARINE...
Marine headlines are not expected through Saturday. Later on
Saturday however, wind gusts are expected to increase to around
20 kts with building seas across the ocean waters. The northern
New Jersey coastal waters may flirt with some 5 foot seas by
later in the afternoon.

Outlook...

Saturday night... Increasing winds/seas. Low-end SCA seas
develop late. Fair most areas but a few tstms for North NJ
waters.

Sunday...SCA possible with enhanced winds/seas in scattered
tstms.

Monday and Tuesday...Mostly sub-SCA. Fair after a few morning
showers Monday.

Rip Currents...

Saturday...South winds around 10-15 mph and breaking waves around
2 feet expected. Portions of the southern New Jersey coast will
maintain an onshore component of the wind, in addition to being
1 day removed from the Full Moon. As a result, have kept a
MODERATE Risk for all New Jersey beaches except Monmouth County.
For the Delaware Beaches and Monmouth County, have kept a LOW
Risk of dangerous rip currents.

Sunday...Southerly winds will increase from 10 mph in the
morning to 20 mph in the afternoon with breaking waves around 2
to 4 feet. Due to increasing winds and higher seas along the
shore, decided to go with a MODERATE Risk for dangerous rip
currents for all NJ/DE beaches. May need to evaluate the
potential for a HIGH Risk of rip currents for southern New
Jersey beaches in future updates.

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

&&

.CLIMATE...

Record high temperatures Saturday.

Location          Record High (6/22)

Philadelphia, PA      100/1988
Allentown, PA         95/1941
Reading, PA           96/1921
Mount Pocono, PA      90/1908
Trenton, NJ           99/1988
AC Airport, NJ        100/1988
AC Marina, NJ         92/1949
Wilmington, DE        98/1988
Georgetown, DE        97/2012

Record high temperatures Sunday.

Location          Record High (6/23)

Philadelphia, PA      97/1888
Allentown, PA         95/1965
Reading, PA           96/1908
Mount Pocono, PA      90/1908
Trenton, NJ           97/1894
AC Airport, NJ        98/1988
AC Marina, NJ         91/1909
Wilmington, DE        100/1894
Georgetown, DE        100/1988

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory until 6 AM EDT Sunday for PAZ054-055-060>062-070-
     071-101>106.
     Excessive Heat Watch from Sunday morning through Sunday
     evening for PAZ054-055-060>062-070-071-101>106.
NJ...Heat Advisory until 6 AM EDT Sunday for NJZ001-007>010-012-013-
     015>020-027.
     Excessive Heat Watch from Sunday morning through Sunday
     evening for NJZ001-007>010-012>027.
DE...Heat Advisory until 6 AM EDT Sunday for DEZ001.
     Excessive Heat Watch from Sunday morning through Sunday
     evening for DEZ001>004.
MD...Excessive Heat Watch from Sunday morning through Sunday
     evening for MDZ012-015-019-020.
MARINE...None.

&&

$$

SYNOPSIS...MPS/OHara/Wunderlin
NEAR TERM...Gorse/Wunderlin
SHORT TERM...OHara
LONG TERM...OHara
AVIATION...Gorse/OHara/Wunderlin
MARINE...DeSilva/Gorse/OHara/Wunderlin
CLIMATE...PHI