618
FXUS61 KPHI 270538
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
138 AM EDT Fri Sep 27 2024

.SYNOPSIS...
A cold front will stall over the southern half of the area
tonight, as moisture from Tropical Cyclone Helene moves in. An
unsettled pattern will continue for the weekend and into next
week as an upper level low meanders off to the southwest. A
pattern change potentially comes by the middle of next week as a
sweeping cold front approaches.

&&

.NEAR TERM /THROUGH TONIGHT/...
130 AM...Overnight, low pressure with its associated upper
trough moves from Quebec towards the Canadian Maritimes dragging
a cold front southward into the area. This could result in some
additional scattered showers and storms, mainly over eastern PA
into central and northern NJ. In fact the front is expected to
slow and stall overnight as it reaches southern NJ and the
Delmarva. The other thing that will have to be watched for
overnight is areas of fog as we`ve already seen visibility down
to a quarter to half a mile in spots. These low visibilities
could become a bit more widespread overnight which would then
warrant a Dense Fog Advisory. It will be another warm night for
this time of year with lows mostly in the mid to upper 60s
except some upper 50s over the southern Poconos and NW NJ.

Helene is forecast to be over northern Georgia on Friday
morning, becoming absorbed into a closed upper level low over
the southeast US. This system is expected to be quite expansive,
and some moisture from the edge of Helene is anticipated to
move in Friday into Friday night.  A stalled boundary over the
Delmarva peninsula will be the focus for precipitation and
currently where the highest PoPs are for Friday
afternoon/evening (around 60-80%). Then rain should then spread
north overnight Friday night into portions of eastern PA and
adjacent NJ. Generally speaking, rain amounts through Friday
night should not be too impressive for most areas...mainly a
tenth to a quarter of an inch or less. That said, expect it to
be a bit heavier at times over Delmarva into southern NJ where
some areas could see a half inch to an inch of rain overnight.

In terms of temperatures for Friday/Friday night, near and
south of the front, high temperatures will be in the mid to
upper 70s, with upper 60s/low 70s north of the front. Overnight
lows on Friday night will be in the upper 50s to low 60s north
and west with upper 60s to around 70 south and east.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
Onshore flow looks to continue Saturday, bringing a cool and
moist airmass. The remnants of Helene will retrograde westward,
with the expansive upper level low positioned over
Kentucky/Tennessee. With the maritime airmass in place, and the
closed low off to the southwest, a few showers could develop,
mainly in New Jersey and eastern Pennsylvania. Will not be a
washout by any means, but more of a cloudy day with some showers
around, similar to what we have seen the past few days. With a
stalled boundary still bisecting the region, temperatures will
be in the upper 60s/low 70s north of Philadelphia, and upper
70s/low 80s from Philly on south.

The upper level low that will eventually absorb Hurricane
Helene will be positioned somewhere over the Ohio River or
Tennessee River Valley on Sunday with the region positioned on
the northeast quadrant of the closed low. This looks to bring
some unsettled weather, but no day will be a washout. We look to
be in for more days of clouds with periods of on and off
showers until the upper level low moves offshore or transitions
to more of an open wave.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The aforementioned upper low will transition into an open wave
sometime Monday or Tuesday, though we will not kick the
clouds/showers until midweek, with guidance hinting at a cold
front coming through and a pattern change (finally).

It certainly will be feeling like fall with cloudy and cool
conditions expected for the end of the weekend and into next
week. Temperatures will be a few degrees below normal for late
September/early October, with upper 60s/low 70s for highs.
Overnight lows may actually end up a few degrees above normal
with limited diurnal ranges continuing with an abundance of
cloud cover in place.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Overnight...Cigs/visbys will continue to lower overnight with
widespread IFR/LIFR expected. Some sites such as ACY could see
visibility get down to a quarter mile. Winds backing to E/NE
around 5 knots as a cold front pushes south into the area.
Moderate confidence on overall trends but low confidence on
specific details.

Friday...IFR, possibly VLIFR cigs/vsby to start the day with
gradual improvement possible to MVFR possible by the afternoon.
Showers possible, mainly across the southern tier. Low
confidence.

Friday Night...Cigs expected to go back down to IFR for most
sites with periods of rain moving through. ABE could stay mainly
MVFR. East winds 5-10 knots backing slightly to ENE overnight.
Low confidence.

Outlook...

Saturday through Saturday Night...Sub-VFR conditions expected
at times, potentially as low as IFR, though stretches of VFR
possible, mainly from KPHL on south.

Sunday through Tuesday...sub-VFR conditions possible with
20-40% chance of showers and low clouds hanging around in
between periods of rain.

&&

.MARINE...
Small Craft Advisory for our waters north of Cape May remains
in effect until 2 AM early Friday morning. This is mainly due to
4-6 ft seas. Southerly winds will generally average 10 to 20
kts.

Sub-SCA conditions Friday with easterly winds less than 10 kts
in the morning, becoming 10 to 20 kts in the afternoon.

Outlook...

Friday Night...No marine headlines expected.

Saturday through Saturday Night...Small Craft Advisory
conditions possible (30-40%), mainly for the New Jersey coastal
waters as seas get near 5 feet.

Sunday through Tuesday...Small Craft Advisory conditions
possible (50%) with seas around 5 feet and gusts nearing 20 kt.

Rip Currents...

For the remainder of today...A High Risk of Dangerous Rip
Currents is in effect until 8 PM for both the Jersey Shore and
Delaware Beaches.

For Friday...East winds around 5-10 mph. Breaking waves heights
of 2-3 feet with a 10-11 second period. As a result, have
maintained a MODERATE risk of the development of dangerous rip
currents for both the Jersey Shore and Delaware Beaches.

For Saturday...East winds around 10-20 mph for Monmouth, Ocean,
and Atlantic Counties with breaking wave heights of 3-4 feet.
Due to onshore flow and higher wave heights, have opted to go
with a HIGH risk of rip currents for these areas. For Cape May
and Sussex Counties, east-southeast winds around 10-15 mph and
breaking waves of 2-3 feet. Due to lesser wind/wave values,
opted for a MODERATE risk of rip currents for these areas.

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...
Tides and water levels continue to diminish through Friday.

The Coastal Flood Advisory remains in effect through Friday
evening for Sussex County, DE as Little Assawoman Bay and the
Indian River Inlet have been slow to drain. Minor tidal flooding
remains likely through the end of the week within the back bays.

The Coastal Flood Advisory in Ocean County remains in effect
through 11 PM tonight, as periods of minor tidal flooding are
expected within Barnegat Bay. No further advisories are expected
thereafter.

Along the Eastern Shore, some spotty minor tidal flooding
remains possible through the end of the week around the night-
time high tide, though no advisories are expected to be needed.

Otherwise, no other tidal issues are expected on the Delaware
Bay, tidal Delaware River, nor the New Jersey coast outside of
Ocean County through the rest of the week.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...Coastal Flood Advisory until 8 PM EDT this evening for DEZ003-
     004.
MD...None.
MARINE...Small Craft Advisory until 2 AM EDT early this morning for
     ANZ450>455.

&&

$$

SYNOPSIS...Robertson
NEAR TERM...Fitzsimmons/MJL/RCM
SHORT TERM...Robertson
LONG TERM...Robertson
AVIATION...Fitzsimmons/MJL/RCM/Robertson
MARINE...DeSilva/MJL/RCM/Robertson
TIDES/COASTAL FLOODING...