690
FXUS61 KPHI 201748
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
148 PM EDT Fri Sep 20 2024

.SYNOPSIS...
Low pressure will continue to spin off of the east coast, while
high pressure will remain from eastern Canada into the eastern
united states through early next week. A weak disturbance is
expected to move across the area Saturday night, before a
stronger low pressure system possibly impacts the area by the
middle of next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
Low pressure will meander some 300 miles east of the Jersey
Shore today through tonight. Meanwhile, surface high pressure
over the southern Province of Ontario will build down into the
eastern Great Lakes and Ohio Valley, and even down into the
southern Appalachians. Clouds will be most prevalent closer to
the coast this afternoon otherwise it will be a mostly sunny
and nice day.

Mainly clear tonight, and with light onshore flow, patchy fog
is possible once again. Saturday will be another mostly sunny
day as high pressure remains ridged over the eastern US.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
The strong low pressure system will continue to meander offshore
through the weekend as a weak high pressure system tries dipping
down the east coast from from eastern Canada. Saturday night, a weak
short wave trough in the mid and upper levels digs into the western
portions of our region. This could result in some showers primarily
west of the I95 corridor. It doesn`t seem to be anything significant
however there`s a moderate (30-50%) chance of showers developing
over central PA. As mentioned by previous shifts, since this is more
due to broader and weaker synoptic scale lift, this does not appear
to be anything widespread or of enough moisture to put a significant
dent in the dry conditions.

The rain chances, at least with this round will be short-lived as
short wave ridging starts to build closer by Sunday morning,
resulting in a return to dry conditions.

Temps will be fairly seasonable within a few degrees of normal for
daytime highs and overnight lows for this time of the year.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
No significant changes with the long term. The high pressure/dry
conditions continue into Monday. However, most guidance still
depicts the return of some much needed rain moving into the region
during the middle of the week.

A messy frontal system is forecast to move eastward as a an area of
low pressure moves across the Ohio River Vally and into the eastern
Great Lakes Tuesday through Thursday. The exact dynamics of what
will cause the rainfall is still a bit uncertain as it may be a
front that swings all the way through or a secondary low pressure
that potentially develops and impacts the area around Thursday.
Either way, ensemble guidance is showing at least moderate (40-60%)
chances for rainfall through the middle of the week which should be
helpful given  conditions have been abnormally dry for the last
month for many areas.

One note, while we currently have rain shower chances from
Tuesday through Thursday, it is unlikely we will see rain
throughout that entire period. Due to uncertainty with how this
system will evolve, it is difficult at this point to further
refine the time period we are most likely to see rain.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

This afternoon...VFR. NE to E winds 5 to 10 kt.

Tonight...VFR expected, however, patchy fog may result in MVFR or
lower conditions. Light N to NE winds.

Saturday...VFR. NE to E winds 5 to 10 knots.

Outlook...

Saturday night...Generally VFR with MVFR or IFR possible in
showers.

Sunday - Monday...VFR conditions expected.

Monday night-Wednesday...VFR prevailing with brief periods of
MVFR or IFR possible in showers.

&&

.MARINE...
Low pressure meanders several hundred miles east of the Jersey
Shore.

Small Craft Advisories are in effect for the ocean waters through
Saturday, primarily for 4 to 6 ft seas. However, there will be
occasional gusts around 25 knots this afternoon. Otherwise, NE
winds will average 15 to 20 kt.

Sub-SCA conditions for Delaware Bay. E winds around 10 kt this
afternoon will turn N tonight.

Outlook...

Saturday night through Sunday night...Small Craft Advisory in
effect on the Atlantic coastal waters due to elevated seas.

Monday-Wednesday...Small Craft Advisory conditions likely
for at least part of this period before we see gradual
improvement especially Tuesday into Wednesday.

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
today and Saturday, and possibly for Sunday as well. NE winds will
range from 15 to 20 mph with gusts up to 25 mph along with 4  to 6
ft breaking waves both today and Saturday.

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

&&

.TIDES/COASTAL FLOODING...
What has changed: Given current tidal departures, there is
increasing concern of minor tidal flooding on the tidal portions
of the Delaware River and on some portions of the Northeastern
Chesapeake Bay. A coastal flood advisory has been issue for some
of these locations for the high tide later today.

Continued onshore flow will result in water piling up and
unable to drain within tidal waterways. At least minor tidal
flooding is expected for the next several high tide cycles for
portions of our area. Moderate tidal flooding may occur for
portions of our area this weekend.

No changes in headlines for the Atlantic coast and Delaware Bay.
We are in the midst of the current high tide cycle and forecast
looks on track. Still increasing confidence in moderate coastal
flooding with high tide cycles this weekend. Will determine if
the watch needs to be updated to a warning as guidance comes in
through the day.

For the tidal Delaware River, there is increasing concern for
widespread minor flooding, starting with the high tide this
afternoon/evening. For now, have only issued the coastal flood
advisory to cover this high tide as will have better confidence
on future high tides once we see departures with today`s high
tide.

For the northeastern shore of Maryland, it looks like the gauge
at Claiborne will just touch advisory threshold with the high
tide this evening. Further north in Kent County Maryland, it
appears that water levels will fall short with this evening`s
high tide. That being said, still increasing concern for tidal
flooding across most of the northeastern Chesapeake with high
tides on Saturday and Sunday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory until 7 PM EDT this evening for PAZ070-
     071-106.
NJ...Coastal Flood Advisory until 3 PM EDT this afternoon for
     NJZ016.
     Coastal Flood Advisory until 6 AM EDT Saturday for NJZ012>014-
     020>027.
     Coastal Flood Watch from Saturday morning through Sunday
     afternoon for NJZ012>014-020>027.
     High Risk for Rip Currents through Saturday evening for NJZ014-
     024>026.
     Coastal Flood Advisory until 7 PM EDT this evening for
     NJZ017>019.
DE...Coastal Flood Advisory until 3 PM EDT this afternoon for
     DEZ001.
     Coastal Flood Advisory until 6 AM EDT Saturday for DEZ002>004.
     Coastal Flood Watch from Saturday morning through Sunday
     afternoon for DEZ002>004.
     High Risk for Rip Currents through Saturday evening for DEZ004.
MD...Coastal Flood Advisory from 5 PM this afternoon to 8 PM EDT
     this evening for MDZ015-019-020.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ450>455.

&&

$$

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