-- Discussion containing changed information from previous version are highlighted. --
172
FXUS61 KPHI 220814
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
414 AM EDT Sun Sep 22 2024

.SYNOPSIS...
Low pressure continues to meander several hundred miles east of
the Jersey Shore, and will gradually slide to the south and
east as the new week progresses. Meanwhile, the base of an area
of high pressure centered over eastern Canada will sag down into
the Northeast and Mid-Atlantic for the start of the new week.
This high will eventually lift to the north and east by the
middle of this week. Low pressure approaches from the west and
will slowly drag a cold front towards the region by the middle
to end of this week. Another area of low pressure may develop on
that front as it approaches.

&&

.NEAR TERM /THROUGH TONIGHT/...
Showers and storms associated with the weak shortwave trough
continue to progress southeastward from Central PA into MD as
they weaken. These showers and storms are expected to remain
generally west of a Philly to Wilmington line, and even in those
locations will likely not bring more than a few hundredths of
an inch of rain. By mid day, the short wave trough will be
southeast of our region, with mid level short wave ridging
building in, bringing a return to dry conditions.

The other weather concern, both early this morning and again
tonight is the potential for fog to develop. For this morning,
we`ve already seen low and mid level clouds build in, so seems
unlikely we`ll see much more than patchy shallow fog. For Sunday
night, there will be less in the way of low/mid level clouds,
but there will be increasing high level clouds. It is uncertain
if this will be enough to suppress fog development, so have
continued with a mention of patchy fog.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
The pesky offshore area of low pressure will be some 350 to 400
miles southeast of Atlantic City Monday morning and will
finally drift out to sea through Tuesday. Meanwhile, high
pressure will be centered over the Canadian Maritimes, and the
base of this high will sag down into the Northeast and Mid-
Atlantic. This will keep conditions dry on Monday with highs in
the low to mid 70s.

Low pressure develops over the Midwest and Ohio Valley and
tracks east on Monday. A cold front will extend down from this
low, and this system will slowly tack east and approach the
Northeast and Mid- Atlantic. High pressure to the north and east
will gradually lift away, but this high will keep the frontal
system from making much headway until the high departs.

The first wave of showers will approach late Monday, but
coverage looks to be limited to the southern Poconos and Berks
county. PoPs increase to low-end chance over the western zones
Monday evening, but rainfall should be minimal.

The base of the high will build back down into the Northeast on
Tuesday, so much of Tuesday should end up dry with seasonal
temperatures in the lower 70s.

The frontal system will be able to make some eastern headway
Tuesday night, and showers will begin to spread east late
Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Unsettled weather on tap for much of the Long Term period.

High pressure over eastern Canada finally departs, allowing low
pressure and its associated cold front to slowly track east. A
mid-level trough approaches from the west, and this may allow a
secondary low to form on the front as it passes through the
region. Showers will become likely for most of the region
Wednesday and Wednesday night as this system passes through.
Cannot rule out a few thunderstorms as well.

There are some timing issues with how long it will take the
front to depart, so showers will continue into Thursday, and
possibly Friday as well. Will follow NBM PoPs and carry chance
PoPs Thursday, slight chance Friday and Saturday, though
Saturday may end up being dry.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through 12Z...MVFR ceilings are building in and should
eventually move over most, if not all TAF sites, although
impacts at most TAF sites probably won`t last long (exceptions
being KMIV, KACY where onshore flow will probably keep the
ceilings in place through at least 12Z). Showers and storms to
the west of most TAF sites, but have already clipped KRDG, and
may approach KILG later. Winds should generally favor
northeasterly, but are light enough (generally 6 kt or less),
that direction could be variable at times. Moderate confidence.

Today...Once the MVFR ceilings dissipate by 15Z (will dissipate
at most TAF sites by 12Z, but could hang on longer at KACY and
KMIV), will have VFR through the remainder of the day. Winds
northeasterly or easterly around 10 kt or less. Moderate
confidence.

Tonight...Prevailing VFR. There is a small chance (20%) that
patchy fog will develop. But confidence is too low in potential
areas as well as the extent to include in the TAFs at this time.
If it does develop, MVFR or even IFR ceilings may be possible.
Moderate confidence.

Outlook...

Monday through Tuesday...VFR, though sub-VFR possible in BR
Monday night.

Tuesday night through Thursday...Periods of MVFR or IFR in
SHRA.

&&

.MARINE...
Small Craft Advisories on the Atlantic coastal waters today and
tonight, primarily due to elevated seas. On the Delaware Bay,
winds and waves should remain below SCA criteria.

Outlook...

Monday through Monday night...SCA in effect for the ocean
waters, mainly for elevated seas.

Tuesday through Thursday...SCA may be needed for elevated seas
into the middle of next week.

Rip currents...

There is a HIGH risk for the development of dangerous and life
threatening rip currents at the Jersey Shore and at Delaware
Beaches through Monday. The persistent onshore flow continues
with NE winds of 10 to 20 mph with gusts up to 25 mph along with
3 to 6 ft breaking waves.

Rip currents occur often in the vicinities of jetties and piers
and the speed of the currents are generally maximized at low
tides.

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

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --
A prolonged period of onshore flow has resulted in, and will
continue to result in, a piling up of water along the coasts
with this water unable to drain within tidal waterways. While
moderate coastal flooding will occur with the high tide cycle
this afternoon for portions of southern New Jersey and along
Delaware Bay, minor coastal flooding will occur elsewhere.
Although headlines are in effect through the Monday afternoon
and Monday night high tide cycles, additional Coastal Flood
Advisories may be needed for the Tuesday afternoon and Tuesday
night high tide cycles.

A Coastal Flood Warning remains in effect until 5 pm this
evening for moderate coastal flooding for Cape May and
Cumberland counties in New Jersey, and for Kent county,
Delaware. Thereafter, a Coastal Flood Advisory is in effect for
these areas through the Monday afternoon high tide cycle. A
Coastal Flood Advisory may be needed for the Tuesday afternoon
high tide cycle.

For the rest of the Atlantic Coast, southern Raritan Bay, and
Delaware Bay, Coastal Flood Advisories remain in effect through
the Monday afternoon high tide cycles. A Coastal Flood Advisory
may be needed for the Tuesday afternoon high tide cycle.

For the tidal Delaware River, Coastal Flood Advisories remain
in effect through the Monday evening high tide cycle for minor
coastal flooding. A Coastal Flood Advisory may be needed for the
Tuesday afternoon high tide cycle.

For the northeastern shore of Maryland, Coastal Flood
Advisories remain in effect through the Monday night high tide
cycles for minor coastal flooding. A Coastal Flood Advisory may
be also needed for the Tuesday night high tide cycle.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory until 10 PM EDT Monday for PAZ070-071-
     106.
NJ...Coastal Flood Advisory until 6 PM EDT Monday for NJZ016.
     Coastal Flood Warning until 5 PM EDT this afternoon for NJZ021-
     023-024.
     Coastal Flood Advisory from 5 PM this afternoon to 5 PM EDT
     Monday for NJZ021-023-024.
     Coastal Flood Advisory until 5 PM EDT Monday for NJZ012>014-
     020-022-025>027.
     High Risk for Rip Currents through Monday evening for NJZ014-
     024>026.
     Coastal Flood Advisory until 10 PM EDT Monday for NJZ017>019.
DE...Coastal Flood Advisory until 6 PM EDT Monday for DEZ001.
     Coastal Flood Warning until 5 PM EDT this afternoon for DEZ002.
     Coastal Flood Advisory from 5 PM this afternoon to 5 PM EDT
     Monday for DEZ002.
     Coastal Flood Advisory until 5 PM EDT Monday for DEZ003-004.
     High Risk for Rip Currents through Monday evening for DEZ004.
MD...Coastal Flood Advisory until 5 AM EDT Tuesday for MDZ012.
     Coastal Flood Advisory until 2 AM EDT Tuesday for MDZ015-019-
     020.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ450>455.

&&

$$

SYNOPSIS...MPS
NEAR TERM...Johnson
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...Johnson/MPS
MARINE...Johnson/MPS
TIDES/COASTAL FLOODING...MPS