279
FXUS61 KPHI 032145
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
545 PM EDT Wed Jul 3 2024

.SYNOPSIS...
High pressure moves offshore and remains east of the area through
the weekend. Low pressure moves well north of the area Thursday
and sends a few weak fronts towards eastern Pennsylvania and
northern New Jersey. These fronts remain in the area through
Saturday before diminishing. Another system arrives for Tuesday
of next week.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
Surface high pressure continues to gradually move off the coast to
our east as a frontal system starts to approach from the west.
However the high will continue to dominate our weather through this
evening bringing continuing mainly clear to partly cloudy skies
along with southerly winds generally around 5 to 10 mph.

As we head into the overnight period tonight, a warm front will be
pushing eastward across PA bringing increasing cloud cover with dew
points also starting to rise. There could be a few showers moving
into our NE PA zones across the southern Poconos by very late
tonight but I think that most likely this will remain to our north
and west so POPs tonight only max out around 15 to 20 percent.
Overnight lows will range from the low to mid 60s across the cooler
spots such as the Pine Barrens and the southern Poconos to the upper
60s around the urban corridor.

High pressure will continue to move offshore into Independence Day
as a surface low and associated upper level trough move eastward
through eastern Canada. This will push the warm front through the
region early in the day Thursday allowing the area to get into the
warm sector. The warm front could continue to bring a few isolated
showers or storms early Thursday morning, mainly over NE PA into NW
NJ, but with the greater chances for showers and storms arriving
later in the day (mainly after 2 PM). Prior to this, the other story
for the day will be the return of the heat and humidity as highs for
most areas will reach the upper 80s to low 90s (cooler near the
coast and over the Poconos) with dewpoints reaching the upper 60s to
low 70s. This will result in max heat indicies into the 90s for most
areas along and south of I-78. Cloud cover is expected to increase
as the day progresses and winds will be from the south to southwest
near 5-10 mph (15-20 mph near the coasts).

As for the storm threat later in the day, expect storms to fire in
the vicinity of a weakening frontal boundary draped over PA by the
afternoon hours with these storms moving eastward into our eastern
PA and northern NJ zones by later in the afternoon and then
potentially affecting Delmarva and southern and coastal NJ by the
evening. So it won`t be an all day type rain event but unfortunately
the timing won`t be great as it could interfere with Independence
Day festivities. Our POPs generally max out around 40% to 50% over
much of the area, though are a bit lower near 30% to 40% near the
coast and across Delmarva and a bit higher (around 60 percent)
around Chester and Berks Counties in SE PA. With ML CAPE values
progged to max out around 1000-1500 J/kg along with deep layer shear
values around 30 knots, there is the potential some storms could
become severe. The SPC has a MARGINAL risk (1/5) for severe
thunderstorms extending east into SE PA and Delmarva though it was
pulled back slightly from the previous forecast. Water loaded
downdrafts could lead to a few strong to locally damaging wind
gusts. Given the shear, convection could exhibit some organization,
though widespread severe convection is not expected at this time.
Most guidance has PWats over 2.0" across the entire area, and
largely within the 2.25" to 2.5" range. These values are near record
PWat values for the month of July at IAD and OKX (read: highly
anomalous). WPC keeps most of our area in a MARGINAL risk for
excessive rain but has upgraded SE PA (including Philly) to a SLIGHT
risk as storms will be capable of producing very heavy rain which
could lead to localized flash flooding...especially if storms set up
over the urban areas of Greater Philadelphia.

Storms may linger into a good portion of the evening Thursday before
diminishing overnight. It will be a very warm and muggy night as the
frontal boundary gets hung up over the area. Most areas won`t see
lows getting below the low/mid 70s (except 60s over the Poconos).
Some fog development is possible overnight where ever rainfall
occurs.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
The last day of the week and into the weekend will feature a continuation
of July-like weather with plenty of warmth and humidity. Highs both
days will be above normal with upper 80s/low 90s common across the
region. Dew points in the low/mid 70s for many areas with perhaps
a few upper 70s for Sat around Delaware Bay.

Precipitation chances will be diurnal mostly with slight chance pops
for the morning and higher pops for the afternoon and evening hours.
Sat will have some likely pops for the afternoon as the upper ridge
will have moved away and more subtle shortwaves traverse the region.
Locally heavy rains are possible for the afternoon and evening
hours.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Saturday night,  the showers and tstms across the area Saturday will
gradually end from west to east overnight. We;ll carry chance pops
for the ern areas and slight chc for the NW sections. Some heavy
rains will taper off during the evening. We are not certain how fast
things will end and its possible that some higher pops may eventually
be needed for the evening. Very warm/hot and humid conditions will
continue.

We`ll settle into a mid-summer pattern Sunday and into next week
with a stretch of above normal temperatures and varying amounts of
humidity expected. Sunday and Monday will feature more comfortable
dew points (humidity) compared to the last days of the forecast. Dew
points Sun/Mon will mostly be in the 60s before climbing into the
low 70s (with upper 60s NW) for the midweek.

Rainfall for Sunday and Monday will be scarce with an upper ridge
banked across the East Coast. This all changes for Tue/Wed as most
op models depict a slow moving front edging into the area. This could
be the focus for frequent showers/tstms during those periods. We
have capped pops in the chance range at this time since the NBM wanted
likely pops over a wide area. Not comfortable with this attm.

&&

.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through 0Z this evening...Mainly VFR with just some Ci clouds
and some diurnal Cu. Light S winds becoming 5-10 kts. High
confidence

Tonight...VFR with no significant weather. Winds generally southerly
around 5 kts. High confidence.

Thursday...VFR in the morning but with increasing clouds. scattered
showers and thunderstorms are expected to develop for the afternoon
into the evening hours (mainly after 18z) and these could bring
restrictions if any of these storms move over a TAF site. The best
chances for this look to be around RDG with lower POPs farther south
and east toward MIV and ACY. Winds mainly southwest around 5 to 10
knots except 10 to 15 knots around ACY. Moderate confidence.

Outlook...

Fri./Fri night... Scattered showers/tstms developing Fri
afternoon and continuing overnight lower CIGS/VSBYS at times.

Saturday... VFR early then scattered showers/tstms developing
for the afternoon/evening with lower CIGS/VSBYS possible.

Sat night... Lower CIGS/VSBYS in showers/tstms diminish
overnight. Patchy fog possible at TAF sites that receive any
rain.

Sunday/Monday... Mostly VFR. Patchy fog possible overnight.

&&

.MARINE...
Sub-SCA with fair weather through tonight. Light S or SE winds
increasing to 10-15 kts.

For Thursday into Thursday night, southerly winds increase to around
15 to 20 knots but should stay below Small Craft Advisory levels.
However showers and storms will be possible over the waters by
Thursday evening and these could bring locally stronger winds.

Outlook...

sub-SCA overall with scattered showers and tstms Fri/Sat and
less so Sunday. Low-end SCA gusts and seas possible for the
Ocean Sat afternoon and evening.

Rip Currents...

Independence Day (Thursday)...Southerly winds strengthen with
breaking wave heights increasing. With an onshore component to the
wind for Cape May, Atlantic, and Ocean County, there is a MODERATE
risk for rip currents. With wind direction more shore
parallel/offshore at the Delaware Beaches and northern Jersey Shore,
have elected to go with a LOW risk. Breaking wave of 2 to 3 feet,
though some 4 foot waves are possible within the MODERATE risk
area.

Friday...A New Moon will occur. Winds weaken a bit from Thursday but
become more onshore for much of the NJ shore. There is a MODERATE
risk for rip currents for Cape May, Atlantic, Ocean, Monmouth
County, and a LOW risk for Delaware Beaches. Breaking waves of 2 to
3 feet.

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

&&

.TIDES/COASTAL FLOODING...
With the New Moon to occur Friday, some locations may see some
spotty minor coastal flooding during the next few high tide cycles.
Any advisory minor coastal flooding is not expected at this time.

&&

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

&&

$$

SYNOPSIS...OHara
NEAR TERM...Fitzsimmons
SHORT TERM...OHara
LONG TERM...OHara
AVIATION...Fitzsimmons/OHara
MARINE...Fitzsimmons/OHara
TIDES/COASTAL FLOODING...