628
FXUS61 KPHI 060205
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1005 PM EDT Fri Jul 5 2024

.SYNOPSIS...
High pressure dissipates offshore this evening. Several waves of low
pressure and weak fronts approach the area through Saturday night,
before a cold front slowly crosses the area on Sunday. High pressure
returns for Sunday night and Monday before another slow moving low
pressure system encroaches upon the area through the middle of next
week.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
Showers and thunderstorms are winding down, though a few
lingering storms may affect portions of northern New Jersey
through midnight or so.

Another round of showers and possible thunderstorms will
approach from the west later tonight, mainly impacting western
portions of the Lehigh Valley and possibly into northern New
Jersey. With dew points well in the 70s and PWATs well in excess
of 2 inches, locally heavy rain is likely biggest concern.

Aside from the overnight convection potential, it will be a
very warm and muggy night, leading to little relief from the
daytime heat. Forecast low temperatures will be largely in the
mid to upper 70s within the Heat Advisory area, and in the low
70s elsewhere. Some areas of fog and/or low stratus development
are possible again, favoring any locations that experience
appreciable rainfall.

We are still maintaining a very active Saturday to start off
the weekend. A very hot and humid airmass remains in place in
combination with an approaching cold front likely brings
numerous showers and thunderstorms across the region. Heat
advisories are up again for the entire region, minus Carbon and
Monroe counties in PA, with heat indicies of 100-105 across the
urban corridor north and heat indicies 105+ for the Delmarva and
extreme southern NJ. In terms of storms, PWAT values will be in
excess of 2 inches across the region, so we are still expecting
the main threat to be locally heavy rain with storms. That
said, isolated severe storms can`t be ruled out given the high
CAPE. Guidance is in a bit of a disagreement where the frontal
boundary will set up by early afternoon. Wherever it does
arrive, we continue to expect numerous scattered showers and
thunderstorms to form along and ahead of the front.

Storms will gradually push south and east offshore as the cold
front crawls along, though it does look to wash out a bit by
early Sunday morning. Some relief with overnight lows cooling to
the upper 60s and low 70s behind the front, though dew points
will lag a bit in the same region, still leading to a slight
cooler, but still rather humid night.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
Not much change in the short-term forecast through Monday. The
cold front still looks on pace to cross the area on Sunday but
as it does so, it will be washing out and moving at a snails
pace. Ultimately, the front should just leave a remnant boundary
behind. As a result, Sunday should be a fairly nice day for
most as high pressure builds in from the north and west with
just a slight chance of showers across the Delmarva and southern
NJ. High temps should again be in the upper 80s to low 90s, but
dew points will fall back into the 60s behind the front. At
this point, no heat headlines are expected, but if the front
hangs up a bit more to the north and west this may need to be
reconsidered. Skies should begin to clear out a bit into Sunday
night except over the Delmarva where a few showers may linger.
Lows will remain though in the upper 60s to mid 70s as moisture
content is still quite high.

High pressure will win out on Monday for most areas leading to
a mostly tranquil day with a mix of sun and clouds during the
afternoon. However, with the remnant boundary lingering overhead
and subtle increase in moisture return with dew points rising
back into the lower 70s, a few showers or thunderstorms will be
possible north and west of the I-95 corridor. As mentioned
above, dew points will be slightly higher and air temps will be
a degree or two higher as well on Monday. Heat indicies will
hover between 95-99 degrees for much of the area. Will continue
to evaluate trends amongst T/Td guidance over the next several
days in order to determine if any heat headlines will be needed
for Monday.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The long term period as a whole is summarized to be quite
unsettled with seasonable temperatures. An upper level trough
will be over the Great Lakes region Monday night into Tuesday
before shifting east over the Northeast US through Wednesday.
But this is where the forecast details becomes uncertain because
there will be several impulses embedded in the upper flow,
allowing several fronts and boundaries to be near our region.
This will result in several opportunities for some showers and
thunderstorms, mostly in the afternoon and evening hours due to
diurnal effects. Right now, the greatest chance for
showers/storms looks to be Tuesday into Wednesday. After
Wednesday, deterministic and ensemble guidance differs
significantly, so have held a chance of showers/storms through
the end of next week to account for variability amongst guidance
suites.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Tonight...Initially VFR. However, some areas of fog and/or
stratus development are possible again with sub-VFR
restrictions. Some isolated showers anticipated between roughly
00-09Z with thunder possible (20% chance). Winds diminish to
around 5 kts or less, favoring a southerly direction. High
confidence in initially prevailing VFR conditions, but low
confidence on the occurrence and timing of any restrictions in
fog/stratus/showers overnight.

Saturday...Lingering fog/low stratus in the morning, giving way
to VFR by mid to late morning. Intervals of sub-VFR returns with
scattered showers and thunderstorms in the afternoon. Low
confidence.

Outlook...

Saturday night...Sub-VFR possible. Showers and storms in the
evening give way to fog/low stratus developing overnight. Low
confidence.

Sunday through Monday night...VFR expected. A slight chance of a
shower or thunderstorm possible Sunday night into Monday. Otherwise,
no significant weather anticipated.

Tuesday through Wednesday...Sub-VFR conditions possible. A chance of
showers and thunderstorms possible with occasional mist/fog.

&&

.MARINE...
Small craft advisories in effect through Saturday evening.

South winds 15-20 kts with gusts near 25 kts across the Atlantic
waters. Seas 4-5 feet build to 4-6 feet Friday night.

Winds and seas remain elevated through the first part of
Saturday with showers and storms possible. Winds and seas begin
to diminish later afternoon/early evening.

Outlook...

Saturday Night...Winds and seas fall below SCA criteria late
evening. Wind gusts to 20 kt. Wave heights up to 5 feet,
diminishing to 3 to 4 feet. Chance TSRA.

Sunday through Monday night...No marine headlines expected. Winds
generally less than 15 kt and seas of 2-3 feet. A slight chance of a
shower or thunderstorm into Sunday night, otherwise fair weather
expected.

Tuesday through Wednesday...No marine headlines expected. Winds
generally less than 20 kt and seas of 2-3 feet. A chance of
thunderstorms expected.

Rip Currents...

The effects of a New Moon today will linger into the weekend. On
Saturday, south winds will average 10 to 15 mph with gusts up to
20 mph. With an onshore component in New Jersey, this results in
a MODERATE risk for the development of dangerous and life
threatening rip currents for the Jersey Shore. Since this
direction is a bit more parallel to the coast, if not a bit
offshore, in Delaware, this results in a LOW risk for dangerous
rip currents at Delaware Beaches.

On Sunday, winds will be lighter and a bit more onshore. This
results in a MODERATE risk for dangerous rip currents at the
Jersey Shore, mainly south of south of Monmouth county. For
Monmouth county and Delaware Beaches, there is a LOW risk for
the development of dangerous rip currents.

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

&&

.TIDES/COASTAL FLOODING...
With the New Moon to occur today, some locations may see some
spotty minor coastal flooding during the next few high tide
cycles.

With continuing S/SE flow and the approach of the New Moon,
some guidance has areas of Cumberland County NJ seeing advisory
minor coastal flooding with the upcoming evening high tide
cycle. Though guidance may be running a bit high, a short-fused
coastal flood advisory may be needed later on.

&&

.CLIMATE...
Near record breaking warmest low temperatures are forecast on
Saturday. Records for our climate sites are listed below:

Record Warmest Low Temperatures
                           July 6
Site                  Record/Year
Allentown (ABE)           74/1999
AC Airport (ACY)          76/1999
AC Marina (55N)           80/1999
Georgetown (GED)          78/2012
Mount Pocono (MPO)        71/1999
Philadelphia (PHL)        79/1999
Reading (RDG)             75/1934
Trenton (TTN)             76/1999
Wilmington (ILG)          77/1999

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory until 8 PM EDT Saturday for PAZ060>062-070-071-
     101>106.
NJ...Heat Advisory until 8 PM EDT Saturday for NJZ001-007>010-012-
     013-015>023-027.
     Air Quality Alert from 11 AM to 11 PM EDT Sunday for
     NJZ008>010-012>015-017>020-026-027.
DE...Heat Advisory until 8 PM EDT Saturday for DEZ001>003.
MD...Heat Advisory until 8 PM EDT Saturday for MDZ012-015-019-020.
MARINE...Small Craft Advisory until 8 PM EDT Saturday for ANZ450>455.

&&

$$

SYNOPSIS...DeSilva
NEAR TERM...MJL/MPS/Staarmann
SHORT TERM...DeSilva
LONG TERM...DeSilva
AVIATION...DeSilva/MJL/MPS
MARINE...DeSilva/MJL/MPS
TIDES/COASTAL FLOODING...
CLIMATE...