569
FXUS61 KPHI 152001
AFDPHI

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

.SYNOPSIS...
High pressure will be in control through Monday Night. An area of
low pressure moves up from the Carolinas for the middle of the week
potentially bringing some heavy rain. Unsettled conditions persist
through the end of the week, though high pressure tries to build in
for the weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
High pressure remains to the northeast across New England. It will
remain in place tonight and much of Monday before weakening. Low
pressure is well to the south over the offshore Carolinas. 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 clear skies tonight and sunny skies
Monday. Like today, there could be some fog overnight mostly in
rural areas. Most of it will be light, but a few areas of thicker
fog can`t be ruled out. 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. East winds 5 to 10 mph.

Monday will be much like today with temperatures perhaps a few
degrees cooler. Mostly mid/upper 70s for highs. Winds East to
Northeast at 10 to 15 mph with gusts 20 to 25 mph near the
shore.

&&

.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 /20Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

.Tonight...  VFR conditions to continue overnight. Skies will
feature high clouds with perhaps a few low clouds near the shore.
East winds around 10 knots this evening decreasing overnight. Patchy
rural fog possible. Not enough confid to include in any TAF site
attm. Medium/high confid.

.Monday... VFR continues with daytime cumulus and some high clouds
too. Northeast to East winds increasing to 10 to 15 knots by mid-
morning. Medium/high confid.

Outlook...

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

Tuesday through Wednesday...Sub-VFR conditions expected ( > 80%
confidence) at times, as low as IFR, with periods of heavy rain
possible. Low clouds will be present in between periods of
rain. Gusts near/over 20 kt possible at KACY/KMIV on Tuesday
afternoon.

Wednesday night through Friday...Sub-VFR conditions possible
with continued chances for rain 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 flags are 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.
Fair tonight and Monday.

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 (50%) as seas hover near 5 feet and gusts get near 25
kt at times.

Rip currents...

Today..East to northeast winds will average 10 to 15 mph with
breaking waves averaging 2 to 3 feet with an 8 to 9 second
period. Due to these conditions, there is a HIGH risk for rip
currents for the Delaware Beaches and Cape May county coast.
For the remaining Jersey Shore, there is a MODERATE risk for the
development of dangerous and life threatening rip currents.

Monday...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 Monday.

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. Right now, the highest tide looks to be Monday night
where some advisories may be needed, mainly for the southern NJ
coast, Delaware Bay, and southern Delaware. 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 Monday evening for NJZ024.
     High Risk for Rip Currents from Monday morning through Monday
     evening for NJZ014-025-026.
DE...High Risk for Rip Currents through Monday evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ451.
     Small Craft Advisory until 6 AM EDT Tuesday for ANZ452>455.

&&

$$

SYNOPSIS...Hoeflich
NEAR TERM...OHara
SHORT TERM...AKL/Hoeflich
LONG TERM...AKL/Hoeflich
AVIATION...AKL/OHara
MARINE...AKL/OHara
TIDES/COASTAL FLOODING...WFO PHI