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696
FXUS61 KPHI 180524
AFDPHI

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

.SYNOPSIS...
An area of low pressure tracks northwestward into the Carolinas
while a secondary low passes off to our east, bringing increasing
chances for showers across our area through midweek. Unsettled
conditions persist through the end of the week and possibly into the
weekend as an area of low pressure lingers offshore though high
pressure will be trying to build in.

&&

.NEAR TERM /THROUGH TODAY/...
-- Changed Discussion --
Minor tweaks made for the early morning update, but nothing of
significance.

A secondary coastal low has spawned off the coast of Cape
Hatteras, breaking away from the parent low over the Carolinas
while lifting northward; paralleling our coastline during the
day on Wednesday. There has been quite a bit of spread amongst
model guidance over the past few days with regard to track of
the secondary low, but the 12Z guidance suite today has come a
bit better in line today. So for now, it appears that the
secondary low will track a bit closer to the coast, but should
remain just far enough offshore where the heaviest of rain will
be focused.

So as we head into tonight, some light showers will begin to
overspread the area across the Delmarva and into southern New
Jersey. As cool and relatively dry northeast flow continues, this
should keep most locales north and west of Philadelphia to remain
dry overnight under mostly cloudy skies. Low temperatures will
generally range in the mid 50s to mid 60s.

The secondary low makes its approach on Wednesday where more in the
way of scattered showers make their way into the area. The best
chance for this occurrence will be along the immediate coast where
coastal convergence is enhanced. Some heavier pockets of rain may
make their way further inland as far west as the I-95 corridor, but
for northern and western most locations, most of the day actually
may remain quite dry. As a result, QPF values will not amount to
much generally 0.10-0.50 inches across the region, with the
highest amounts up to 1 inch found near the coast. Given the
fact that there has been limited rainfall in recent weeks, WPC
maintains no mention of excessive rainfall for our region, so
the flood threat is quite low.
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&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
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 ern NJ are the most favored spots to see any
rain. Temperatures will be close to normal with highs in the
mid/upper 70s Thu and a little above normal Fri when more low 80s
will be expected and upper 70s for the shore areas of NJ/Delmarva.

&&

.LONG TERM /FRIDAY NIGHT 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 skinny 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. The pattern continues into Monday as well.

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. Overnight lows generally in the mid 50s to low 60s Saturday
then widespread 50s for Sun/Mon.

&&

.AVIATION /05Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of Tonight...VFR for the Lehigh Valley terminals, with
MVFR/IFR conditions developing for the I-95 terminals. Ceilings
will end up right around 1000 feet, so some fluctuation between
IFR and MVFR likely by late tonight. IFR at KACY with MVFR at
KMIV, who will eventually go down to IFR for CIGs. Some light
scattered showers around, but not expecting any visibility
impacts. Winds out of the northeast around 5-10 kt. Moderate
confidence in timing and extent of restrictions.

Wednesday...VFR for the Lehigh Valley terminals. MVFR and IFR
conditions for the I-95 terminals will continue through the
morning with some improvement during the afternoon back to VFR
as ceilings lift. KMIV will likely stay MVFR through the day
with IFR prevailing at KACY. Some showers remain possible,
mainly from the I-95 corridor on east. Heavier downpours around
KACY could result in brief lower visibility. Northeast winds
5-10 kt, gusting 15-20 knots in the afternoon, especially for
ACY and MIV. Moderate confidence overall, but lower confidence
with timing of improving conditions.

Wednesday Night...Primarily VFR for the Lehigh Valley and I-95
terminals. Low ceilings hang around the New Jersey coast,
resulting in either MVFR or IFR ceilings at KMIV and KACY. 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.
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&&

.MARINE...
A Small Craft Advisory is in effect for the Delaware Bay until 10
AM on Wednesday. A Small Craft Advisory is in effect for the
Atlantic Coastal Waters through Wednesday.

SCA conditions will continue across all waters tonight with east-
northeast winds around 15-20 kt and gusts up to 25-28 kt. Seas of 5-
7 feet on the ocean waters with a moderate chop on the bay waters.
For Wednesday, similar conditions will be found on the ocean waters,
but conditions will gradually abate across the Delaware Bay below
SCA thresholds. Showers likely with isolated thunderstorms
possible.

Outlook...

We will extend the ending time for the present SCA flag until 6 AM
Thu morning. Seas through that time will remain above 5ft.
There will likely be a period of sub-SCA conditions centered
around Friday before more enhanced winds/seas arrive for
Saturday. There will be some scattered showers Thu/Thu night
then mostly fair weather is expected for Fri and 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...
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Coastal Flood Advisories for tonight`s high tide (Cape May,
Atlantic, and Cumberland in NJ and Sussex and Kent in
Delaware) have expired. Will go ahead and re-issue later this
morning as some minor flooding is expected, but could go longer
than one tidal cycle with the next advisory.

We also will likely need to issue further advisories for the
rest of the NJ coast at some point later this week with
prolonged onshore flow and water piling up, but tonight`s high
tide only produced spotty minor flooding within Ocean,
Monmouth, and Middlesex Counties. Flooding concerns will be
primarily with the evening high tide as it is the higher of the
astronomical tides but spotty minor flooding is forecast with
the morning high tide as well and may become more widespread
during this tide cycle as well later in the week as water piles
with the sustained onshore winds.

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.
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&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None.
NJ...High Risk for Rip Currents through this evening for NJZ014-024>026.
DE...High Risk for Rip Currents through this evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ430-
     431.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ450>455.
-- End Changed Discussion --

&&

$$

SYNOPSIS...Hoeflich/OHara
NEAR TERM...DeSilva/Hoeflich/Robertson
SHORT TERM...OHara
LONG TERM...OHara
AVIATION...DeSilva/Hoeflich/OHara/Robertson
MARINE...AKL/DeSilva/OHara
TIDES/COASTAL FLOODING...AKL/Hoeflich