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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 251103
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
703 AM EDT Mon Sep 25 2023

.SYNOPSIS...
The remnants of Ophelia will drift slowly southward and
offshore through Wednesday, resulting in onshore flow and some
lingering rain, especially toward the coast. High pressure builds
over southern Quebec and the Northeast states, pressing southward
through early Thursday. An upper level low passes by late in the
week, but otherwise high pressure will expand southward from New
England down the Appalachians through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Another dreary day is expected across the region as the remnants of
Ophelia continue to spin through the region early this morning
before moving offshore. Latest observations place the low to the
southeast of Philadelphia, in South Jersey. Areas of rain and
drizzle continue to pivot around the low, mainly on the northern
side with the heaviest rain just to the north of our region across
northeastern PA and southern NY.

This pattern of drizzle closer to the low with relatively heavier
areas further north will continue as the low spins off to the
southeast and offshore late this morning/early this afternoon. This
action will draw the more concentrated precip back into the northern
portions of our area but accumulations are expected to be light with
little in the way of instability. Less than 0.50 inches is expected
across most of the area with localized totals around 1 inch
possible, across northwest New Jersey and the southern Poconos where
upslope along the terrain may provide a bit of extra forcing.

The other main concern as the remnant low moves offshore will be
increasing winds and wind gusts, particularly at the immediate shore.
With a tightening pressure gradient, gusts as high as 35 to 40 mph
will be possible at the immediate coast, with gusts generally around
20 to 30 mph inland. These higher gusts will initially be limited to
the northern Jersey Shore before spreading from north to south as
the low continues to pivot away offshore. By late tonight/early
Tuesday, the higher gusts will be possible across the entire
Atlantic Ocean coast of New Jersey as well as the Atlantic coast of
Delaware.

Otherwise, with the overcast skies temperatures will continue to be
rather cool with highs mainly in the 60s today before decreasing
into the 50s tonight.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Tuesday through Wednesday will feature a blocking ridge over eastern
Canada, with strong surface high pressure slowly building southward
from Quebec across New York and New England, as the synoptic pattern
across the eastern US remains rather slow-moving and stagnant.
Meanwhile, our weather locally will be largely determined by the
remnant area of low pressure from former Tropical Storm Ophelia,
which will drift slowly southeastward off the mid-Atlantic coast.
The low will eventually drop to east of Cape Hatteras by late
Wednesday, though model guidance is in some disagreement on the
exact placement by that point. Not completely unlike the pattern we
have been dealing with all weekend, the key component here will be a
strong pressure gradient between the aformentioned high to the north
and low pressure drifting south. That will drive strong onshore flow
at least on Tuesday, gradually easing on through Wednesday as the
low drifts farther away.

While more dynamic forcing will be lacking compared to the weekend,
and stronger isentropic lift will be positioned farther offshore,
there will be enough low-level moisture advection and convergence,
particularly toward the shore and the Delmarva, to keep overcast
skies along with light rain. This will be aided by frontogenesis
along a baroclinic zone, as cooler air in association with the high
to the north presses southward against our prevailing warm, moist
airmass. Initially, dewpoints along the coastal plain Tuesday
morning will be in the upper 50s and low 60s, but will drop through
the 50s heading into Tuesday night, with some 40s making their way
southeast to I-95. That will represent some drier air and subsidence
making it`s way in aloft as well, allowing for at least some partial
clearing skies northwest of I-95 Tuesday night through Wednesday.
Clouds will persist to the southeast. The misty rain will only add
up to perhaps a quarter-inch or so along the immediate coast from
Tuesday through Wednesday, with only around a few hundredths back to
the urban corridor on Tuesday. That will be accompanied by a raw
northeast breeze, occasionally gusting to 20 mph inland, with
downright windy conditions along the immediate coast, with gusts
over 30 mph common. Those winds will ease substantially on
Wednesday, but it will remain rather breezy, mainly overcast and a
little damp near the coast. Some drying and breaks in the clouds may
make it down to Tom`s River. Highs both days will be only in the low
to mid-60s, with Tuesday being the coolest day of the week. This
stretch of early autumn weather will represent some of our coolest
daytime temperatures since early May.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Blocking high pressure centered over Quebec will remain in control
Thursday, but will weaken with associated surface high pressure
shifting east across New England. That will maintain relatively cool
onshore flow, but will at least allow the airmass to modify more,
with high temperatures approaching 70 from near Philadelphia
southward. Unfortunately, that will also allow for a weak upper-low
near Lake Michigan to escape eastward, reaching the northern mid-
Atlantic by Thursday night. That suggests that skies will probably
stay mostly cloudy Thursday. Have a slight chance of showers late
per NBM guidance, but to be honest that seems doubtful given the
position of the surface high still wedging down the Appalachians,
keeping the low-levels rather dry. Even by Friday when NBM has low
chance showers in, the surface high remains, so that any showers
that make it in will likely be spotty and light at worst. Later
shifts may consider pulling shower chances altogether.

By Saturday, that upper low will push quickly offshore. A rather
strong late-season ridge will expand and shift eastward from the
Plains across the Ohio and Tennessee Valleys through the weekend,
with broad surface high pressure drifting down the Appalachians.
Kept some slight chance POPs in on Saturday and down to the coast on
Sunday per NBM, but that looks aggressive as well. If the pattern
holds on the next model run or two, later shifts should probably
trend more optimistic. In fact, next weekend could turn out very
pleasant. We have highs in the forecast warming into the low to mid
70s, but warmer than that is a good possibility given then pattern,
and that may be accompanied by more sun than clouds as well.

&&

.AVIATION /11Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Monday...IFR ceilings may lift to low-end MVFR through the day.
Occasional MVFR visibility during some rain especially north of PHL.
North to northeast winds 5-10 knots, increasing to 15-20 knots with
gusts up to 25 knots from mid-morning into the afternoon. Strongest
winds should be closer to the coast. Low confidence.

Monday night...MVFR/IFR gradually improving towards high-end MVFR.
Continued periods of rain possible, particularly closer to the
coast. Gusts largely dropout with northeasterly winds becoming
sustained around 10 to 15 kts, with the higher speeds closer to the
coast. Low confidence, especially on timing of any improvements.


Outlook...

Tuesday...Starting out MVFR to IFR ceilings everywhere, with misty
light rain especially from I-95 to the coast resulting in MVFR to
IFR VSBY, especially in the morning. CIGS improve to VFR ABE/RDG,
MVFR I-95 TAF sites. Winds NE 10-15 G 20 kt, with G 30 kt near the
coast. Moderate confidence.

Wednesday... MVFR to IFR from I-95 to the coast at least in the
morning due to ceilings. Some lingering light rain near the coast.
Improvement to VFR possible I-95 northwestward. Winds NE 10-15 kt.
Moderate confidence.

Thursday through Saturday...Mainly VFR. NE-E winds around 10-15 kt.
Low confidence.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
As the remnant low of Ophelia continues to track near our area,
multiple marine hazards remain.

As we head through the day, waters north of Little Egg Inlet will
see the development of Gale force wind gusts of up to 40 knots as
northeasterly winds restrengthen. Seas will also build to 7 to 9
feet in this area. Therefore, a Gale Warning is in effect for
this area and will continue through Monday night. Coastal
waters south of Little Egg Inlet but north of Cape May will
continue to see SCA conditions so the SCA will continue through
the day for these areas. Seas south of Cape May as well as on
the Delaware Bay will be less than 5 feet with winds around 10
knots.

As we head into this evening, conditions will begin to degrade
further, particularly south of Cape May and on the Delaware Bay.
Northeasterly winds restrengthen in this area with gusts increasing
to 25 to 30 kts and seas on the ocean increasing to 7 to 9 feet.
Therefore, new Small Craft Advisories are in place beginning at 6 PM
and 8 PM on the Delaware Bay and for Atlantic Ocean waters south of
Cape May respectively. These will continue through Monday night as
will the SCA for Atlantic Ocean waters south of Great Egg Inlet. The
strengthening winds this evening will cause gusts off the coast of
Atlantic County to strengthen to Gale force as well so the SCA for
ANZ452 will be converted to a Gale Warning as well beginning at
6 PM.


Outlook...

Leftover remnant low pressure from former Tropical Storm Ophelia
will continue sinking southward off the southern NJ/DE/MD coast
Tuesday, eventually pushing southeast to offshore of Cape Hatteras
later Wednesday. Meanwhile, strong high pressure pushing in from New
England will result in another tight pressure gradient, with strong
onshore winds through Tuesday, lessening on Wednesday. Extended the
Gale Warning through midday on Tuesday, as we are forecasting gusts
near 34 kt north of Atlantic City. SCA conditions will continue over
Delaware Bay until Tuesday evening when winds finally start to ease,
but elsewhere over the adjacent ocean, advisories will likely
continue right into the end of the week at least due to seas. Either
way, nasty conditions overall Tuesday with rough seas building to
around 9-11 ft. Seas will lower to around 6-8 ft on Wednesday, with
NE winds still gusting to around 25 kt. Additionally, there may be
some VSBY restrictions in misty light rain, especially on Tuesday.

Thursday through Saturday...SCA conditions likely due to seas. NE
winds around 15-20 kt. Seas 4-6 feet.


Rip Currents...

A west to northwest wind 5 to 10 mph is expected for the Delaware
Beaches and for Cape May County in New Jersey on Monday. Breaking
waves should be around 2 to 5 feet with the higher waves along the
shore of Cape May County. As a result, we have been able to lower
the rip current risk to MODERATE for those areas for Monday. An
increasing north to northeast wind is anticipated for the coastline
from Monmouth County down to Atlantic County on Monday with breaking
waves of 4 to 6 feet along the Atlantic County shore and 5 to 7 feet
further north. Those areas will likely continue to experience a HIGH
risk for the development of dangerous rip currents at that time.

The increasing northeast wind and building surf will affect the
entire New Jersey coast and the Delaware coast on Tuesday. All areas
will again be under a HIGH risk for rip currents.

The elevated risk of rip currents will likely continue through much
of the balance of the new week.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Water levels with the evening and overnight high tide cycle were
not quite as high as expected, and we were able to cancel the
Coastal Flood Advisories early. As of the predawn hours Sunday,
all sites are below minor flood stage. Would not rule out some
very spotty minor flooding at times today in some of the back
bays, mainly along the Ocean County (NJ) and Sussex County (DE)
coast.

Otherwise, the focus will shift toward Tuesday, and to a lesser
degree tonight. First things first...the model guidance suggests
that while some spotty minor flooding will be possible along the
NJ shore and coastal DE, water levels will fall shy of advisory
thresholds. Later shifts will keep an eye on it, though. Heading
into Tuesday, with strengthening onshore NE winds, reaching
low-end gale force gusts in some areas, and building seas on the
open ocean over 10 feet, combined with rising astronomical
tides (the full `Harvest` Moon on Friday)...some sites look like
they will breach the moderate coastal flood threshold. Have
issued Coastal Flood Watches proactively for coastal Kent,
Sussex in DE, and the Atlantic and Cape May County coasts. Other
sites along DE Bay and farther north along the NJ shore and back
bays will probably see minor flooding during Tuesday evenings
high tide as well. Thankfully by Wednesday the onshore flow will
weaken and seas will subside, which should limit the severity of
coastal flooding, but some minor flooding will still be a
possibility near high tide Wednesday evening.


.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Watch from Tuesday afternoon through Tuesday
     evening for NJZ022>025.
     High Risk for Rip Currents through Tuesday evening for NJZ014-025-
     026.
DE...Coastal Flood Watch from Tuesday afternoon through Tuesday
     evening for DEZ002>004.
MD...None.
MARINE...Small Craft Advisory from 6 PM this evening to midnight EDT
     Tuesday night for ANZ430-431.
     Small Craft Advisory until 6 AM EDT early this morning for
     ANZ450-451.
     Gale Warning until 6 PM EDT Tuesday for ANZ450-451.
     Small Craft Advisory until 6 PM EDT this evening for ANZ452.
     Gale Warning from 6 PM this evening to 6 PM EDT Tuesday for
     ANZ452.
     Small Craft Advisory until 8 AM EDT Wednesday for ANZ453.
     Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Wednesday for ANZ454-455.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...None.
NJ...Coastal Flood Watch from Tuesday afternoon through Tuesday
     evening for NJZ022>025.
     High Risk for Rip Currents through Tuesday evening for NJZ014-025-
     026.
DE...Coastal Flood Watch from Tuesday afternoon through Tuesday
     evening for DEZ002>004.
MD...None.
MARINE...Small Craft Advisory from 6 PM this evening to midnight EDT
     Tuesday night for ANZ430-431.
     Gale Warning until 6 PM EDT Tuesday for ANZ450-451.
     Small Craft Advisory until 6 PM EDT this evening for ANZ452.
     Gale Warning from 6 PM this evening to 6 PM EDT Tuesday for
     ANZ452.
     Small Craft Advisory until 8 AM EDT Wednesday for ANZ453.
     Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Wednesday for ANZ454-455.
-- End Changed Discussion --

&&

$$

SYNOPSIS...Dodd
NEAR TERM...AKL
SHORT TERM...Dodd
LONG TERM...Dodd
AVIATION...AKL/Dodd
MARINE...AKL/Dodd
TIDES/COASTAL FLOODING...