564
FXUS61 KPHI 172047
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
447 PM EDT Tue Sep 17 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 WEDNESDAY/...
A secondary coastal low will spawn off the coast of Cape Hatteras
this evening 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.

&&

.SHORT TERM /WEDNESDAY NIGHT 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 /21Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of Today...A mix of MVFR/VFR ceilings expected for the rest of
the day with a cloud deck around 2500-4000 feet. East winds around 5-
10 kt occasionally gusting up to 15 kt. Moderate confidence.

Tonight...MVFR/VFR ceilings to continue before dropping to MVFR at
all terminals by 03-04Z. Ceilings should fall to IFR for almost all
terminals by 08-09Z. Occasional showers possible. East-northeast
winds around 5-10 kt. Moderate confidence, but lower confidence with
regard to timing.

Wednesday...MVFR/IFR ceilings expected with periods of rain and
showers through the afternoon. Northeast winds around 10 kt gusting
up to 15-20 kt in the afternoon. Low confidence.

Outlook...

Wed night... Areas of lower CIGS/VSBYs with scattered showers,
especially near the shore areas.

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

&&

.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...
Coastal Flood Advisories remain unchanged for tonight`s high
tide (Cape May, Atlantic, and Cumberland in NJ and Sussex and
Kent in Delaware) as minor tidal flooding is expected.

Given the uncertainty with the upcoming pattern, continue to
elect to just maintain the advisory for just tonight`s high
tide, though extensions remain possible if not likely. 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 should only
produce 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 with the high tide
tonight and beyond.

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 until 1 AM EDT Wednesday for NJZ021>025.
     High Risk for Rip Currents through Wednesday evening for NJZ014-
     024>026.
DE...Coastal Flood Advisory until 1 AM EDT Wednesday for DEZ002>004.
     High Risk for Rip Currents through Wednesday evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 10 AM EDT Wednesday for ANZ430-431.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ450>455.

&&

$$

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