393
FXUS61 KPHI 181047
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
647 AM EDT Wed Sep 18 2024

.SYNOPSIS...
An area of low pressure dissipates across southern Appalachia
while a secondary low slowly organizes off the Mid Atlantic
coast, bringing increasing chances for showers across our area
through midweek. Unsettled conditions persist through the end of
the week and possibly into the weekend this offshore low
lingers with weak high pressure struggling to build in from the
west.

&&

.NEAR TERM /THROUGH TONIGHT/...
Showers continue to overspread the area this morning as an area of
low pressure is developing near the mouth of the Chesapeake Bay.
Only minor tweaks to the PoPs made with the daybreak update. This
weak coastal low will gradually move up the coast through today
and tonight, ending up about 100 miles east of Long Beach
Island by tomorrow morning. This will keep a moist onshore flow
in place. Meanwhile, an upper level low over the western
Carolinas continues to spin, with a shortwave lifting up the
eastern side of the closed low into our area, aiding shower
development. This setup will result in a cloudy and dreary
period through tonight with off and on showers and perhaps some
heavier downpours, especially along the coast. Rainfall amounts
will be around a half inch to an inch over southern Delmarva and
the New Jersey coast, with around a tenth to a quarter of an
inch around the I-95 corridor and gradually decreasing amounts
into the Lehigh Valley and southern Poconos. WPC introduced a
very small MARGINAL risk for excessive rainfall for the New
Jersey coast as any heavy rain that does fall could result in
ponding on some roadways due to poor drainage from higher tides.

Temperatures today will be in the low to mid 70s. With a somewhat
tropical airmass in place and lots of cloud cover, temperatures will
not drop much tonight, with low to mid 60s anticipated.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
It`ll remain unsettled across most areas during the short term. An
upper trough will remain across the region and the weak surface low
offshore will continue to circulate low level moisture across the
area. Clouds will be widespread across NJ/Delmarva and less so for
the western counties. Scattered showers are possible both Thu/Fri,
but the areas across eastern NJ are the most favored spots to
see any rain. Temperatures will be close to normal with highs in
the mid/upper 70s Thu before cooling a few degrees headed into
Friday with highs largely in the low to mid 70s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The upcoming weekend looks rather benign across the Middle Atlantic.
The upper trough that has been across the area late this week will
weaken allowing a weak ridge from the west to move in. At the
surface, high pressure well to the northeast ridges back across
the Northeast and northern Middle Atlantic. Overall, no
significant wet weather makers but since the airmass will be
humid and somewhat onshore, a few daytime showers are possible.
We`ll just have slight chance pops for Sat/Sun with the
coastal/Delmarva areas (probably) most favored. Monday now looks
drier with weak high pressure finally shifting overhead. Drier
weather sticks around into Tuesday before the next system begins
to move in from the west later in the day.

Temperatures will be close to normal Saturday with mid/upper 70s for
highs most areas. After that, the onshore flow and more clouds will
keep readings a bit cooler than normal with mostly low 70s for
highs.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...Primarily VFR at the Lehigh Valley terminals, though
some MVFR stratus has developed at KRDG/KABE. Thinking that
scatters out by the late morning. Otherwise, no issues there.
For the I-95 terminals, IFR to start for CIGs which should lift
to MVFR by the late morning. Beyond that, the forecast becomes
tricky. All 4 I-95 corridor terminals will be right on the edge
of MVFR stratus through the afternoon and evening with ceilings
around 2-3k feet. Have included a brief period of VFR though
some terminals could stay MVFR if stratus stays far enough
inland. For the South Jersey terminals, primarily IFR through
today though KMIV could lift to MVFR for the afternoon. Some
scattered showers around, though no visibility restrictions
expected with the exception of KACY where some heavier downpours
are possible, potentially reducing visibility briefly to 4-5
miles or so. Winds out of the northeast around 10 kt with some
gusts upwards of 20-25 kt possible at KACY/KMIV and 15-20 kt at
KPHL/KILG. Moderate confidence in forecast through the morning,
low confidence for the afternoon/early evening.


Tonight...Primarily VFR for the Lehigh Valley terminals. MVFR
expected at the I-95 corridor terminals with IFR expected at the
South Jersey terminals as stratus overspreads New Jersey into
the Philly metro area. Winds out of the north/northeast around
5-10 kt. Moderate confidence overall.



Outlook...

Thu thru Sunday... Mostly VFR. Widely scattered showers with short
periods of lower CIGS/VSBYs possible.

&&

.MARINE...
For the Delaware Bay...The Small Craft Advisory was cancelled for
the upper Delaware Bay where gusts should remain below 25 kt. A
Small Craft Advisory remains in effect until 10 AM for the lower
Delaware Bay as gusts near 25 kt are possible, mainly near the mouth
of the bay. For the afternoon and overnight period, no marine
headlines expected for the bay as winds will be around 10-20 kt out
of the northeast.

For the ocean zones...Small Craft Advisory in effect through
Thursday as seas around 5-7 feet are expected. Winds out of the
northeast around 15-20 kt with some gusts around 25 kt.

Outlook...

SCA for ocean zones will now be extended through 6PM Thursday.
Seas through that time will remain above 5ft. Additional
extensions are likely, with seas expected to build into the
weekend, upwards of 7 feet. NNE winds Thursday around 15-20 kts
will ramp up on Friday, flirting with 25+ kt gusts into the
weekend.

Rip currents...

For Wednesday, east winds will decrease slightly to around 15
mph but breaking waves remain 2 to 4 feet with an 8 to 9 second
period. Therefore, the HIGH risk for the development of rip
currents was maintained and a Rip Current Statement remains in
effect through Wednesday for all beaches.

For Thursday, winds are forecast to shift more shore parallel
out of the north-northeast and decrease to 10-15 mph. Breaking
waves also decrease slightly to 2-3 feet with a 6-8 second
period. Currently, a MODERATE risk for the development of rip
current is forecast for all beaches as a result.

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

&&

.TIDES/COASTAL FLOODING...
Continued onshore flow will result in water piling up and unable
to drain within tidal waterways. Minor tidal flooding is
expected for at least the next several high tide cycles for
portions of our area.

Coastal Flood Advisories were posted for the New Jersey coast,
Delaware Coast, and part of the Delaware Bay (Cumberland County
in New Jersey and Kent County in Delaware) as minor tidal
flooding is expected around high tide through the end of the
week at least. As a result, the Coastal Flood Advisory is not
just for tonight`s high tide, but through the high tide Friday
afternoon. Some of the guidance indicates moderate flooding
towards the end of the week, but will stick with the advisory
for now.

For the upper Delaware Bay and the tidal Delaware River, only
spotty minor tidal flooding is expected for this week.

No tidal flooding is expected along the northeastern shore of
Maryland currently at the moment.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Advisory from 7 PM this evening to 3 PM EDT
     Friday for NJZ012>014-020>027.
     High Risk for Rip Currents through this evening for NJZ014-024>026.
DE...Coastal Flood Advisory from 7 PM this evening to 3 PM EDT
     Friday for DEZ002>004.
     High Risk for Rip Currents through this evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ431.
     Small Craft Advisory until 6 PM EDT Thursday for ANZ450>455.

&&

$$

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