325
FXUS61 KPHI 152242
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
642 PM EDT Sun Sep 15 2024

.SYNOPSIS...
High pressure will be in control through Monday night. An area
of low pressure tracks northwestward into and across the
Carolinas through the middle of this week, bringing increasing
chances for showers across our area. Unsettled conditions
persist through the end of the week, though high pressure tries
to build in for next weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 640 PM, the daytime heating induced cumulus have nearly
dissipated across our area as they shift westward. Some drier
air has advected into our area from the north and northeast. No
significant changes needed with this update.

Otherwise, high pressure remains centered to the northeast
across New England. It will remain in place tonight and much of
Monday before weakening. Low pressure is located offshore of
the Carolinas (now designated Potential Tropical Cyclone
Eight). Our region is in modest onshore flow between the two
systems, so the weather is basically fair with mild
temperatures. The pattern looks to continue into Monday, so
while a mainly clear sky is expected tonight there may be some
stratus that develops toward morning closer to the coast. Any
stratus early Monday morning mostly across the coastal plain
should lift into a cumulus deck and then advect inland. In
addition, some high level clouds are expected to stream in from
the south. There could be some fog overnight although just
enough drying may have occurred to limit this to some open
fields and/or valleys. Lows tonight will range in the low/mid
50s for most areas, but upper 50s/low 60s near the metro
Philadelphia region and for Delmarva.

Temperatures on Monday are forecast to be cooler than Sunday
with mostly mid/upper 70s for highs. Winds east-northeast 10 to
15 mph with some gusts 20 to 25 mph especially closer to the
coast.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
Monday Night onward looks to bring our first rain in over week.
An area of non-tropical low pressure is developing along a
stalled boundary off the southeastern US. It could take on
tropical or sub- tropical characteristics being over the Gulf
Stream, with the National Hurricane Center giving it a 50%
chance of developing into a tropical/subtropical system as of 2
PM EDT. This system looks to move into the Carolinas on
Monday/Monday Night, gradually moving north/northwestward and
then eventually slowly off to the north/northeast. Latest
guidance has the center of the low tracking further northwest
into the Carolinas/western Virginia before turning north. This
would keep a slightly slower progression with the bulk of the
incoming moisture holding off until daytime Tuesday. Still
thinking the Tuesday afternoon and evening will be the wettest
overall, with the heaviest rain concentrated south of
Philadelphia. There perhaps could be some embedded thunderstorms
but the main concern will be the tropical-esque downpours as
PWATs surge toward 2 inches.

Rainfall amounts currently are around 1-2 inches basically from
Wilmington and Atlantic City on south through Wednesday.
Amounts of half inch to an inch through Wednesday are expected
around Philly with gradually diminishing amounts further north.
WPC has the entire region in a MARGINAL risk for excessive
rainfall currently on Tuesday and/or Wednesday, which is about
right as guidance has been very inconsistent with the evolution
of this system as it pushes north, and the axis of heaviest
rainfall could certainly shift. We also have been very dry as of
late, and thinking if the heaviest rain stays out of the urban
areas, flooding issues will be minimal overall.

With the tropical airmass overspreading the area, it will feel quite
muggy both Monday and Tuesday nights. Overnight lows will only drop
into the 60s. Highs on Tuesday and Wednesday will be in the mid
to upper 70s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A relatively stagnant pattern will likely exist for the back
half of the week, with a closed upper low level low somewhere
in the vicinity. This will result in unsettled conditions
through Friday, with rain chances around 25-45% through that
period. Stuck close to the NBM overall for this period as the
late week forecast is highly dependent on what happens with this
area of low pressure approaching for the early/middle portion
of this week. Most of the deterministic and some of the
ensembles want to try to have a ridge build in for the weekend,
but again, a highly uncertain forecast overall.

Given the abundance of moisture and onshore flow setting up for most
of the long-term period, expect muggy days and lots of cloud cover.
This will suppress daytime highs to be near/just below normal with
mild overnight lows and less of a diurnal range of temperatures.

&&

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

Tonight...VFR, however some low clouds may develop toward
daybreak closer to the coast (KACY and KMIV) and some localized
fog cannot be ruled out. East-northeast winds around 10 knots
will diminish. Low confidence if fog/stratus develops and impacts
any terminals.

Monday...Some low clouds possible in the morning, otherwise VFR
with some cumulus and also high level clouds. East-northeast
winds increasing to 10-15 knots through the morning, with some
gusts to 20-25 knots mainly at KACY. Low confidence regarding
low clouds in the morning.

Outlook...

Monday night...Low clouds begin to develop with MVFR/IFR CIGs.

Tuesday through Wednesday...Sub-VFR at times, as low as IFR,
with showers some of which could produce locally heavy rain. Low
clouds will be present in between showers. Wind gusts near/over
20 knots possible at KACY/KMIV on Tuesday afternoon.

Wednesday night through Friday...Sub-VFR possible with
continued chances for showers and low clouds.

&&

.MARINE...
High pressure well to the northeast and low pressure to the south
will keep the onshore flow continuing into Monday. Winds and seas at
SCA criteria for the southern areas where a Small Craft Advisory
remains in place. We`ll start the next zones northward (all
except ANZ450) with the next issuance since the higher seas are
making good progress that way.

Outlook...

Monday night...Small Craft Advisory in effect for coastal
waters south of Manasquan Inlet as gusts over 25 kt and 5-6 foot
seas are expected. The lower Delaware Bay may need to be added
as gusts look to approach 25 kt. Sub-SCA conditions expected
along the upper Delaware Bay and coastal waters north of
Manasquan Inlet.

Tuesday through Friday...Small Craft Advisory conditions
possible as seas hover near 5 feet and gusts get near 25 kt at
times.

Rip currents...

For Monday and Tuesday, east winds will average 15 to 20 mph
with breaking waves of 2 to 4 feet with an 8 to 9 second
period. This results in a HIGH risk for the development of
dangerous and life threatening rip currents for the Delaware
Beaches and Jersey Shore. A Rip Current Statement is now in
effect for both Monday and Tuesday.

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

&&

.TIDES/COASTAL FLOODING...
Continued onshore flow will result in some minor tidal
flooding, mainly along the Atlantic coast and within the
Delaware Bay. Spotty minor flooding could begin as early as
tonight`s high tide. Coastal Flood Advisories may be needed
starting with the Monday night high tide, and then Tuesday night
and possibly Wednesday morning. Biggest impacts look to be
along the southern New Jersey and Delaware coasts, and along
Delaware Bay. Will continue to monitor trends and issue any
advisories as needed but coastal communities mentioned above
should prepare for some minor tidal flooding.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...High Risk for Rip Currents through Tuesday evening for NJZ024.
     High Risk for Rip Currents from 6 AM EDT Monday through Tuesday
     evening for NJZ014-025-026.
DE...High Risk for Rip Currents through Tuesday evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ451>455.

&&

$$

SYNOPSIS...Gorse/Hoeflich
NEAR TERM...Gorse/OHara
SHORT TERM...AKL/Hoeflich
LONG TERM...AKL/Hoeflich
AVIATION...AKL/Gorse/OHara
MARINE...AKL/MPS/OHara
TIDES/COASTAL FLOODING...