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Office: PHI

FXUS61 KPHI 110139
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
939 PM EDT Wed Aug 10 2022

.SYNOPSIS...
A stationary front will remain in place tonight into Thursday
across the Delmarva while a wave of low pressure rides eastward
along it. A stronger cold front will then cross our region
Thursday night into Friday. High pressure will build across the
region for Saturday before weakening Sunday. Another storm
system will arrive early next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
A frontal boundary will remain stalled out across the southern
portions of the area through tonight, before an area of low
pressure moves along this boundary later tonight through
Thursday morning, eventually pushing the front south of the
area. A secondary cold front is expected to approach the area
from the northwest later on Thursday as well.

The first round of showers and tstms has rolled across Delmarva
and is clipping Cape May County NJ attm where out first (land)
warning was recently issued. The activity seems to be diminishing
but another round of activity is possible later tonight and through
daybreak Thursday. This second round of precipitation is associated
with the passage of a wave of low pressure that will be moving
along the frontal boundary while another short wave/vorticity
impulse moves into the area. PW values remain high around 2+
inches, so another period of heavy rain will be possible,
especially if any training or backbuilding occurs.

On Thursday, showers and thunderstorms will likely be ongoing for
a portion of the area after daybreak for a few hours before the
showers move offshore. The front will move offshore during the morning
as the low shifts to the northeast. Once these showers move offshore,
a mostly dry day is likely to occur for the rest of Thursday. A few
showers may occur late in the afternoon across the higher elevations
as the secondary front moves into the area, but these will be light
and isolated at best.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
Main feature during the short term is the cold front and upper
trough which will be diving southeast into the area. The front
itself will enter the region late Thursday and cross the region
Thursday night. The frontal passage will likely try to push a
few showers southeastward across the area with it. Still
uncertain about coverage and they should be brief, so for now
kept minimal POPs in the forecast.

However, strong and deepening upper trough will drop into the
area late at night into early Friday, and as winds aloft start
to turn more parallel to the front, it should slow down. This
deepening upper trough may in fact try to induce cyclogenesis
along the front, though not expecting much true low pressure to
develop. However, this does throw some flies into the ointment
as the dry Friday forecast is looking somewhat iffy. Some
guidance even develops some rather intense showers or even
thunderstorms early Friday morning, though this is the other end
of the spectrum compared to the dry forecast we had. Given the
trend, added some chance pops along the coast where precip
development looks most likely.

The system will gradually slide further east off the coast
Friday night into Saturday, so kept POPs generally confined to
Friday daylight. Very dry air moves in behind it, so by Saturday
expect plenty of sunshine with possibly nudging into the 40s. If
it were not for the drought watch for parts of the area, it
would unquestionably be a nearly perfect day for an August
weekend.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
High pressure will remain in control as it slowly slides east
across the region Saturday night and Sunday. This will allow a
slight recovery in temps and dew points on Sunday after a
comfortably cool Saturday night, but overall, it will remain
quite pleasant for August.

Things get much more uncertain Monday thru Wednesday next week,
but the trend is for a considerably wetter pattern. Latest
guidance is heading strongly in the direction of a closed low
aloft helping to develop a coastal surface low pressure Monday,
with the system being quite slow moving such that it lingers at
least into Tuesday. Still much uncertainty, but this could
result in a couple of unseasonably cool, wet and breezy days.
Given the recent dry stretch, this may be very beneficial, but
locally heavy rain and a gusty onshore wind could result in some
modest flood and coastal concerns. Still several days to watch
it, and this system could end up evolving significantly
differently, but the latest GFS and EC are remarkably similar.

One thing that's not too uncertain is that the pattern in
general will remain cool, as the mean trough will remain nearby.
This will ensure temps stay mostly below normal for highs, but
lows may be more elevated due to cloud cover.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR conditions begin the night period through this
evening, before MVFR ceilings develop across southwest
Pennsylvania, southern New Jersey, Delaware, and eastern
Maryland. IFR conditions are possible for southern New Jersey,
Delaware, and eastern Maryland There will be a chance of
showers and thunderstorms for the  late overnight and toward
daybreak, generally after 07z. These showers or thunderstorms
could lead to lower conditions. Winds overnight will be light
and variable around 5 knots for most areas, with a west to
northwest direction for more sustained areas.

Thursday...MVFR or IFR conditions are expected to begin the
period across southwest Pennsylvania, southern New Jersey,
Delaware, and eastern Maryland before lifting to VFR. Northern
Pennsylvania and northern New Jersey will likely remain VFR
through the period. There is a chance of showers and
thunderstorms for the morning hours, before they move offshore
by midday. Winds will increase out of the northwest 5-10 knots
through the morning into the afternoon.

Outlook...
Thursday night-Friday...predominantly VFR, tho a brief interval
of sub-VFR possible with any passing showers. Winds NW to N 5-10
kts. Moderate confidence.

Saturday-Sunday...VFR. Winds northerly 5-10 kts Saturday switch
to west-southwest Sunday at similar speeds. High confidence.

Monday...potential for sub-VFR intervals as low pressure may
develop near the area, producing showers. Winds southeasterly
5-10 kts. Low confidence.

&&

.MARINE...
Although winds and waves expected to remain below advisory
level conditions, winds could gust around 20 knots at times.
Higher winds and waves will be possible near thunderstorms.

Outlook...

Thursday night-Friday...potential for brief small craft advisory
conditions behind a cold front with winds becoming northerly
10-15 kts with gusts to 20 kts, potentially nudging up to 25
kts briefly. Seas 3-4 ft, potentially building to 5 ft briefly.

Saturday-Sunday...sub-SCA conditions expected with northeasterly
winds around 10 kts Saturday becoming southwesterly Sunday. Seas
2-4 ft.

Rip currents...

A east to southeast wind of 5 to 10 MPH is forecast this
afternoon. Breaking waves are expected to be 1 to 2 feet with a
medium period south to southeast swell. There is a LOW risk for
rip currents along the coasts of Delaware and New Jersey today.

A variable wind 5 to 10 MPH on Thursday morning is anticipated
to become onshore in the afternoon. Breaking waves should be
around 1 foot with a medium period south to southeast swell.
Again there will be a LOW risk for rip currents on Thursday.

&&

.TIDES/COASTAL FLOODING...
The full moon occurs on Thursday evening. The evening high
tides today, Thursday and Friday will be particularly high even
without any contribution from the wind.

Some localized tidal flooding is possible this evening in the
coastal counties of New Jersey and Delaware, and along Delaware
Bay. The minor tidal flooding may become more widespread on
Thursday evening and Friday evening. The latest forecast
guidance suggests that we may need advisories for parts of our
region at those times.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$
Synopsis...RCM
Near Term...Robertson/po
Short Term...RCM
Long Term...RCM
Aviation...RCM/Robertson/po
Marine...RCM/Robertson/po
Tides/Coastal Flooding...WFO PHI