321
FXUS61 KPHI 180133
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
933 PM EDT Sat Aug 17 2024

.SYNOPSIS...
A warm front is forecast to lift north across the area later tonight
into Sunday. A cold front is forecast to move across the area later
Sunday into Sunday night and stall near the area into Monday.
Another frontal boundary is expected to move across the area later
Monday into Monday night, followed by a final boundary on Tuesday.
High pressure is expected to control the weather for the remainder of
next week.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
Minor tweaks were made this update, but nothing significant
overall. An active and unsettled Sunday awaits with flooding and
severe potential in addition to dangerous rip currents at the
beaches. Previous full discussion follows...

Low pressure passing over the Great Lakes will help nudge a
warm front to our west slowly into the region tonight while
Hurricane Ernesto passes well off the coast. Convective activity
has been a bit underwhelming so far, with just some showers
moving through. Things will not remain quiet for long as
southerly flow will help a warm front trek northward across the
forecast area early Sunday morning, helping develop an initial
round of heavy showers and thunderstorms across the region. PWAT
values at this point will be pushing into the 2 inch range as
southerly flow will tap into some tropical moisture and
supporting heavy downpours. Latest guidance suggests the
heaviest rainfall from this round will be focused along the I-95
corridor and the fall line where some modest topographic
influence may occur. Timing of this first round will be a few
hours before and after sunrise, likely pushing north of the
region by mid to late morning.

A brief lull is possible late morning/early afternoon, though
isolated to scattered showers and storms will remain possible
during this time. Our second round of heavy rain and storms for
the day looks to begin forming across eastern PA during the
early/mid afternoon as the cold front associated with this
system begins its eastward trek across the region. At this time,
the upper level trough will begin to dig and support increased
baroclinic forcing along the front. Dew points will rise into
the low to mid 70s with PWATs over 2.0 inches ahead of this line
of storms. As a result, rainfall forecasts of widespread 1-3
inches total are expected with local amounts of 4 inches or more
possible. With this in mind, a Flood Watch was issued for the
I-95 corridor and areas north & west into the Lehigh Valley and
Berks County.

Additionally, though daytime heating will be limited, there is
a bit of uncertainty if there will be any breaks in the clouds.
If any amount of daytime heating does occur, instability and
lapse rates could jump and increase the severe potential for the
afternoon and evening. Still a lot of uncertainty with this
potential to form, but with deep layer shear around 30kts,
parameters could become sufficient to support severe
thunderstorms with the best conditions across southern NJ and
the Delmarva. SPC has placed this region into a Slight Risk (2
of 5) for severe weather. High temperatures in the afternoon
look to be in the low-80s.

Heavy showers and strong storms look to persist into the evening
hours and move offshore after midnight or so. Flooding and
severe risks will persist until the convection departs the
region. Overnight lows will cool into the mid 60s to around 70.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
On Monday, the front that moved across the area later on Sunday will
remain near the area as is stalls near the coast. During the day, a
secondary boundary is expected to move across the area. This will
lead to an increased chance of showers and thunderstorms later in
the afternoon and evening, before helping to push the initial
boundary out of the area.

On Tuesday, as the fronts from Sunday/Monday move farther offshore,
a final boundary is expected to move across the area during the day
and could bring a final push of light showers across the area. The
main thing to notice on Tuesday will be the below normal
temperatures

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Quiet weather is expected to dominate the long term period as high
pressure will be moving in from the west through the day Wednesday.
The high centers itself near the area Thursday into Friday, before
shifting offshore late Friday into Saturday. Dry weather is expected
for the entire extended period Wednesday through Saturday. Below
normal temperatures are expected Wednesday, then they inch closer to
normal but still below Thursday, returning to right around normal
Friday, then back above normal Saturday. All in all, a nice second
half of the week into the weekend.

&&

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


Tonight...VFR to start for most sites with showers increasing in
coverage after midnight or so. Some thunderstorms could be mixed
in as well, especially later tonight mainly along and west of
the I-95 corridor. Expecting a mix of MVFR/IFR conditions as
ceilings come down and reduced visibility in heavier downpours
and/or thunderstorms. Winds out of the east/southeast around
5-10 kt. High confidence in restrictions occurring, moderate to
low confidence in timing and extent of restrictions.

Sunday...Conditions start out IFR/MVFR and should lift to VFR at
most, if not all terminals as model guidance continues to
indicate a lull in showers and thunderstorms for the midday time
period. Widespread afternoon/showers and thunderstorms expected,
that will continue into the night that will bring IFR conditions
at times. Winds out of the southeast around 5-10 kt with gusts
up to 20 kt possible at KACY. Higher gusts possible in
convection as well. Moderate confidence in timing of conditions
lifting to VFR. Low confidence in where bulk of
showers/thunderstorms set up.

Sunday Night...Restrictions possible for the night as some
showers/thunderstorms linger with patchy fog developing as well.
Southeast winds around 5 kt. Low confidence overall.

Outlook...

Monday-Monday night...Generally VFR. Chance of showers which could
temporarily lead to lower conditions. West-northwest winds5-10
knots, shifting to northwest and with gusts 15-20 knots possible
Monday night.

Tuesday...Mostly VFR. Chance of showers which could temporarily
lead to lower conditions. Northwest winds 5-10 knots, with gusts
around 15-20 knots.

Tuesday night-Thursday...VFR conditions expected. Northwest winds 5-
10 knots, becoming westerly on Thursday.

&&

.MARINE...
Small Craft Advisory in effect for the ocean through Sunday
night as seas build to 5 to 7 feet due to larger swells from
distant Hurricane Ernesto. Sub-SCA conditions expected for
Delaware Bay. VSBY restrictions in showers and thunderstorms
beginning Sunday morning and through Sunday night. Locally gusty
winds possible with thunderstorms.

Outlook...

Monday-Monday night...Small Craft Advisory conditions continue
through Monday night as seas remain elevated.

Tuesday-Thursday...Conditions expected to lower below advisory
levels Tuesday and remain below advisory levels through
Thursday.

Rip Currents...

Large swells originating from Hurricane Ernesto are propagating
toward our region through the weekend and potentially into the
early portion of the week.

For Sunday...South-southeast winds around 15-20mph. Breaking
waves between 4-7 feet possible with a 11 to 13 second period.
As a result, have maintained a HIGH risk for dangerous rip
currents for both the Jersey Shore and Delaware Beaches.

For Monday...Winds go more south/southwesterly and weaken to
around 10-15 MPH. However, wave heights will be around 3 to 6
feet with an 11 second period. With the upcoming full moon and
low tide occurring in the afternoon, have elected to extend the
HIGH risk for rip currents for the Jersey Shore into Monday.
With the wind direction being more offshore, and lower wave
heights expected off the Delaware coast, have gone with MODERATE
risk for dangerous rip currents at the Delaware Beaches.


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

&&

.TIDES/COASTAL FLOODING...
Widespread minor coastal flooding is expected this evening, and
especially tomorrow evening as an approaching Full Moon, combined
with steady south/southeasterly flow, and swells from passing
Hurricane Ernesto impact tidal communities. A Coastal Flood Advisory
remains in effect for tonight within the tidal Delaware River and
upper Delaware Bay. The Advisory was extended through tomorrow
night`s high tide cycle for these locations as further minor tidal
flooding is expected. In the lower Bay, and along the NJ and DE
coast, only spotty minor tidal flooding is expected for tonight.

Tomorrow night`s high tide will bring widespread minor tidal
flooding with a Coastal Flood Advisory in effect for all tidal zones
with the exception of the Chesapeake. Guidance has been underdoing
high tide levels, as it usually does with passing tropical systems,
and have had to nudge up the forecast slightly. Regardless, some
inundation of low lying areas is possible tonight and especially
tomorrow night, though not expecting flooding to get to moderate
levels at this time.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from 2 AM EDT Sunday through late Sunday night for
     PAZ060>062-070-071-101>106.
     Coastal Flood Advisory until 5 AM EDT Monday for PAZ070-071-
     106.
NJ...Coastal Flood Advisory until 1 AM EDT Monday for NJZ016.
     Flood Watch from 2 AM EDT Sunday through late Sunday night for
     NJZ001-007>010-012-013-015>019.
     Coastal Flood Advisory until midnight EDT Sunday night for
     NJZ021.
     Coastal Flood Advisory from 6 PM Sunday to midnight EDT Sunday
     night for NJZ012>014-020-022>027.
     High Risk for Rip Currents through Monday evening for NJZ014-
     024>026.
     Coastal Flood Advisory until 5 AM EDT Monday for NJZ017>019.
DE...Coastal Flood Advisory until 1 AM EDT Monday for DEZ001.
     Flood Watch from 2 AM EDT Sunday through late Sunday night for
     DEZ001.
     Coastal Flood Advisory until midnight EDT Sunday night for
     DEZ002.
     Coastal Flood Advisory from 6 PM Sunday to midnight EDT Sunday
     night for DEZ003-004.
     High Risk for Rip Currents through Sunday evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ450>455.

&&

$$

SYNOPSIS...Robertson
NEAR TERM...Hoeflich/MJL
SHORT TERM...Robertson
LONG TERM...Robertson
AVIATION...Hoeflich/MJL/Robertson
MARINE...Hoeflich/MJL/Robertson
TIDES/COASTAL FLOODING...Hoeflich