327
FXUS61 KPHI 100756
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
356 AM EDT Fri May 10 2024

.SYNOPSIS...
Multiple waves of low pressure will affect the area today
through Sunday bringing a generally unsettled weather pattern.
High pressure builds south of the Mid-Atlantic region Sunday
night into Monday. Another area of low pressure may affect the
area with more unsettled weather by the middle of next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of early this morning, low pressure was centered near the
mouth of the Chesapeake Bay along an associated east to west
oriented frontal boundary and instability gradient. Meanwhile in
the upper levels a slow moving positively tilted long wave
trough was centered near the eastern Great Lakes. The
combination of these features will continue to bring multiple
waves of rain and showers to the area through the day today.
There has even been some thunder over southern Delmarva where
there exists some elevated instability. The threat for thunder
will actually decrease though heading into the day today as the
lingering instability will be shunted more to our south.

As we head into the day today, the first wave of rain/showers
will move off the coast but there will be additional waves
moving through bringing more rain as the upper trough slowly
progresses towards the region keeping positive vorticity
advection situated over the area. This will tend to keep the
surface low anchored near the coast of Virginia much of the day
while high pressure builds in to the north and east over the
Canadian Maritimes. This will keep the area in periods of rain
with the heaviest and steadies likely occuring over eastern PA
into NJ closest where the strongest PVA will be. The gradient
between the high to the north and the low to the south will also
lock in brisk east/northeast winds that will increase to 15 to
20 gusting upwards of 25 to 30 mph as we get into the day today.
This will add to the rawness of the day with highs for most
areas remaining stuck in the 50s (in the Poconos it may not get
out of the 40s).

As we go into tonight, the upper trough finally sweeps eastward
off the coast taking the surface low with it. This will bring
the steadier rain to an end through the evening from west to
east but there may be some patchy lingering drizzle into the
overnight under a low overcast. Total rain amounts by this time
should be generally in the .50 to 1.0 inch range except some
higher totals of up to 1.25 inches possible over the southern
Poconos into NW NJ. This isn`t expected to cause any major hydro
concerns. Otherwise, some clearing may finally occur towards
dawn Saturday as the winds turn more northerly. It will be a
chilly night with lows mostly in the 40s and even some upper 30s
possible in the southern Poconos.

For Saturday, we`ll get a brief respite in the unsettled
weather as shortwave ridging builds in. In fact most areas
should also see a little sun as the low stratus should start to
break up before clouds increase again by late day ahead of the
next system. The daytime hours should stay mainly dry though
with just a slight chance for some late day showers over our far
western zones from Berks County into Lehigh Valley. Expect
highs mostly in the low to mid 60s except 50s near the coast
and over the southern Poconos.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
The unsettled weather pattern will continue through Sunday.
By Saturday evening, the next wave of low pressure will arrive
out of the Great Lakes, increasing chances for showers,
particularly west of the Philly at night, and centered more on
Philly during the day Sunday. Showers continue to move into the
region Sunday (PoPs 55-65 percent) with lows again in the mid-
upper 40s. Highs will be cooler on Sunday, with 50s to near 60
common.

Main change this evening was to slow the arrival and departure
of precip and increase PoPS a bit, with more likelies Saturday
night into Sunday, but nothing above 10 percent during the day
Saturday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A brief period of dry weather is expected beginning Sunday
night and continuing into Monday as high pressure briefly builds
to the south of the Mid Atlantic region. This dry weather will
only be brief as chances will begin to increase Tuesday night
into Wednesday as a storm system approaches from the southwest.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Through today...Periods of rain and drizzle with cigs lowering
to MVFR or lower through the predawn hours. All sites should
then be IFR by 12z. Rain/drizzle continues through the day with
IFR generally predominating accept some improvement to low MVFR
possible by late day. East/northeast winds increasing to around
10 to 15 gusting at times 20 to 30 knots. Moderate confidence.

Tonight...Steadier rain ends in the evening but lingering low
stratus and some drizzle. This should keep conditions mainly low
MVFR or IFR at least through the evening. Some improvement will
be possible by the overnight as northerly winds start to bring
in drier air. Northeast winds around 10 knots shifting to
northerly and diminishing to 5 knots overnight. Moderate
confidence.

Saturday...Low stratus still possible early in the day with sub
VFR conditions but improvement to mainly VFR by late morning.
Northerly winds 5 to 10 knots shifting back to east then
southeast by late day. Moderate confidence.

Outlook...

Saturday night-Sunday...Sub-VFR conditions probable (50-60
percent chance) at times through the period with chances (40-50
percent) for showers.

Sunday night-Tuesday...VFR conditions expected through Monday.
Sub- VFR conditions with chances for showers return late
Tuesday.

&&

.MARINE...
Winds/seas ramping up through this morning and we
are now expecting a period of Gale conditions today for most of
our ocean zones off the coast of NJ. The exception will be our
northern zone off the coast of Monmouth County. Elsewhere,
widespread Small Craft Advisory conditions. These conditions
will start to improve by late day but still expect it to remain
at Small Craft Advisory levels through Saturday over our ocean
zones, mainly due to seas.

Outlook...

Sunday through Tuesday...Overall, mainly sub-SCA conditions
expected through Monday. Stronger winds may bring SCA conditions
back late Monday into Tuesday.

&&

.TIDES/COASTAL FLOODING...
The new moon occurred Tuesday, May 7th, and this is resulting
in high astronomical tides. As a front settles to our south, an
onshore flow will develop and strengthen some through the end
of the week, peaking Friday into Friday night. While the
astronomical tides will be gradually lowering as we get farther
away from the new moon, the onshore flow should increase the
surge values at least some. With this combination, widespread
minor tidal flooding is again expected with the high tide
tonight into early Friday morning for the Atlantic coastal
zones, the Delaware Bay, and the tidal Delaware River. As a
result, the Coastal Flood Advisories remain in effect for these
areas.

With the peak onshore flow leading up to the Friday night high
tide cycle, guidance continues to support potential for
moderate tidal flooding for portions of Atlantic coastal New
Jersey and Delaware, as well as Delaware Bay with the Friday
night to early Saturday morning high tide cycle. The Coastal
Flood Watch was expanded to include southeastern Burlington and
Ocean Counties. As of the 5 PM Thursday forecast update, our
confidence is highest that coastal Sussex (DE) and Cape May
Counties are the most likely locations to see moderate coastal
flooding impacts Friday night, thus the Coastal Flood Watch was
upgraded to a Warning for those two counties.

Elsewhere within the Coastal Flood Watch area, there is
somewhat lower confidence that moderate tidal flooding impact
will be experienced. Thus, the Watch remains in effect.
Regardless, widespread minor tidal flooding is expected within
the Watch area and adjacent areas of the Atlantic coast of New
Jersey, Delaware Bay, and the tidal Delaware River with the
Friday night to early Saturday morning high tide cycle.
Examination of tonight`s observed water levels and surge values
and additional guidance will be used to determine which areas
will need to be upgraded to a warning or to an advisory for
Friday night.

The Friday night high tide cycle looks to be the peak of the
coastal flooding impacts area-wide, but additional minor
coastal flooding is forecast with the evening/overnight high
tide Saturday night into early Sunday.

Flooding is not expected at this time for our Maryland zones
along the Chesapeake through Saturday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory until 6 AM EDT early this morning for
     PAZ070-071-106.
NJ...Coastal Flood Watch from this evening through late tonight for
     NJZ020>022-025>027.
     Coastal Flood Warning from 8 PM this evening to 4 AM EDT
     Saturday for NJZ023-024.
     Coastal Flood Advisory until 6 AM EDT early this morning for
     NJZ017>019.
DE...Coastal Flood Watch from this evening through late tonight for
     DEZ002.
     Coastal Flood Warning from 8 PM this evening to 4 AM EDT
     Saturday for DEZ003-004.
MD...None.
MARINE...Small Craft Advisory until 1 PM EDT this afternoon for ANZ430-
     431.
     Small Craft Advisory until 6 PM EDT Saturday for ANZ450-454-
     455.
     Gale Warning until 5 PM EDT this afternoon for ANZ451>453.

&&

$$

SYNOPSIS...AKL/Fitzsimmons/OHara
NEAR TERM...Fitzsimmons
SHORT TERM...MJL/RCM
LONG TERM...MJL
AVIATION...Fitzsimmons/MJL/OHara/RCM
MARINE...Fitzsimmons/MJL/OHara/RCM
TIDES/COASTAL FLOODING...