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260
FXUS61 KPHI 231108
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
708 AM EDT Thu May 23 2024

.SYNOPSIS...
A cold front will approach the area today before crossing
through the area this evening. The front will stall to our
south on Friday before lifting back north on Saturday as a warm
front. Another cold front moves through on Sunday, with a
stronger system impacting the area on Monday into Tuesday. High
pressure returns on Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
First round of storms are underway. Forecast remains on track
this morning.

Latest satellite and radar imagery shows a cluster of thunderstorms
becoming more organized across southwest PA and shifting ENE towards
central PA early this morning along and ahead of the advancing cold
front across eastern OH and western PA. Hi res guidance depicts the
cold front advancing across PA this morning and bringing this
organized cluster of storms across the region after sunrise this
morning. Ahead of the storms, forecast soundings show a modest
increase in southwesterly mid level flow in the morning, allowing
for a better LLJ to bring some elevated moisture and instability
into the region. Around 1000 J/kg of MUCAPE and 30-40 kt of deep
layer shear will develop this morning to fuel some stronger to
marginally severe thunderstorms as this cluster arrives. Timing of
these storms look to arrive in eastern PA by around 12Z(8AM) and
push into NJ by 14-16Z (10AM-12PM) and mainly impact areas north and
west of the I-95 corridor during this time.

As the front arrives and bisects the region, it will become quasi-
stationary near and just south of the I-95 corridor and gradually
sag southward through the afternoon and evening. At this time,
another mid level shortwave shifts overhead to provide some
additional baroclinic forcing along this front. Some high res
guidance depicts a second round of scattered showers and
thunderstorms developing and riding along the frontal boundary,
Depending on how worked over the environment will be after the
morning cluster of storms and where any residual outflow boundaries
set up, we could see some strong to marginally severe thunderstorms
across the Delmarva and southern NJ with this second round. Locally
damaging winds will be the main hazard throughout the day,
especially where storms are able to become more organized such as in
a cluster or a line segment.

Any showers and thunderstorms are expected to be weakening and/or
moving offshore Thursday night as the cold front shifts to our east,
though portions of southern NJ and the Delmarva could see scattered
showers linger through daybreak early Thursday morning. Further
north and west, drier air will gradually filter in throughout the
overnight period. Patchy fog cannot be ruled out, especially where
rain occurs and if the cloud cover clears enough.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Friday continues to look like a pleasant day with warming
temperatures into the mid 80s with 70s along the shore due to
the sea breeze. A cold front will move offshore and stall south
of the area on Friday. A few residual showers may linger along
the shore in the morning but for the most part all precipitation
should be over. Skies will clear behind the front as dewpoints
fall back into the 50s. The pleasant and quiet weather will
continue into Friday night with clear skies and light winds. We
should be able to radiate pretty well initially leading to some
patchy fog development over DelMarVa where the heaviest rain is
forecast to fall on Thursday. Clouds will increase from south to
north later in the night which should limit the amount of
cooling late, and thus the expansion of fog across the northern
portions of the forecast area.

For Saturday, the stalled boundary to our south will begin to
lift back northward across the area as a warm front with the
main low pressure system tracking across the Great Lakes. Early
morning on Saturday likely stays dry however, as we progress
through the afternoon, the chance for showers and thunderstorms
increase from west to east. For locations along the shore,
precip may hold off entirely until Saturday evening, although it
will be pretty cloudy most of the day. This system will be a
rather quick mover so while Saturday night does appear to be
wet, all precipitation should come to an end by early Sunday.
Aided by warm air advection, highs on Saturday should reach
again into the low to mid 80s despite cloud cover with cooler
temps along the coast. Saturday night lows will be in the mid
50s to low 60s.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
After precip wanes on Sunday morning, a weak cold front will
pass through the area, however the front will be slowing down
and stalling either over or again just south of the area. Sunday
for now does appear to be mostly dry behind the front with
partial sunshine. Beyond Sunday, the weather pattern becomes
unsettled as a stronger low pressure system develops back over
the central CONUS. Strong PVA will move over the region Monday
with stronger cold front crossing the area Monday night into
Tuesday. This will lead to widespread shower activity across
the region. WPC has included a Slight risk for Excessive
Rainfall, and CIPS analog guidance is highlighting the potential
for severe weather with between a 15-30% chance of severe
weather across PA and 10-15% chance for DelMarVA and NJ. Will
continue to monitor and focus attention on this time period of
Monday afternoon through Tuesday. After the cold front passes,
unsettled weather continues to be the theme thanks to several
waves/impulses aloft passing through the week.

Temps for the workweek should be fairly seasonable with highs
in the low to mid 80s Sunday followed more seasonable 70s
through the week. Lows should be falling into the 60s each
night.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Today...Showers and thunderstorms around resulting in a time of
sub-VFR conditions. First round of storms in the morning hours
will impact terminals along the I-95 corridor and points north
and west. Second round of storms in the afternoon and evening
will likely impact KMIV/KACY more. Southwest winds 5-10 knots,
becoming west to west-northwest behind the cold front. Gusty
winds possible with stronger thunderstorms. Low confidence in
timing and coverage of showers/storms.

Tonight...Lingering scattered showers and thunderstorms could
result in brief sub-VFR conditions early in the evening, mainly
for KMIV/KACY, but coverage should diminish later into the
nighttime hours. VFR conditions should largely return overnight,
though KACY looks to see lower visibilities and cigs as showers
will linger around here a bit longer. That said, some patchy
fog cannot be ruled out, especially across locations that see
rainfall earlier in the day. Low confidence.


Outlook...

Friday through Friday night...VFR. Slight chance of a shower.

Saturday through Saturday night...VFR during the day, likely
becoming sub-VFR at night. Showers and thunderstorms late in the day
into the evening.

Sunday...VFR. No significant weather expected.

Sunday night through Memorial Day...Sub-VFR conditions probable
with a chance of showers and thunderstorms.
-- End Changed Discussion --

&&

.MARINE...
The conditions are expected to remain below Small Craft Advisory
criteria through Thursday night, however a few gusty thunderstorms
will be possible especially Thursday afternoon and evening.

Outlook...

Friday through Monday...No marine headlines expected. Winds will
periodically gust up to 15-20 kt with seas around 2-4 feet. A chance
for showers and thunderstorms is expected on Saturday night and for
Sunday night into Monday.

Rip Currents...

S to SW winds will average 5 to 10 mph on Thursday along with
breaking waves around 2 feet. There is a LOW risk for the
development of dangerous and life threatening rip currents at NJ
and DE beaches for Thursday. However, showers and thunderstorms
are likely, and may be capable of strong wind gusts and hail.

On Friday, winds will once again be out of the S to SW at 5 to
10 mph with breaking waves of 1 to 2 feet. There is a LOW risk
for the development of dangerous and life threatening rip
currents at NJ and DE beaches for Friday. Although there is a
slight chance for showers, thunderstorms are not expected.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will be elevated this week with a Full Moon
on Thursday, May 23. Spotty minor coastal flooding will be possible,
especially for the back bays, around the times of the evening high
tide cycle, which will be the higher of the two tide cycles, going
into the end of this week.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Deal/DeSilva
NEAR TERM...MJL
SHORT TERM...Deal/DeSilva
LONG TERM...Deal/DeSilva
AVIATION...Deal/DeSilva/MJL
MARINE...Deal/DeSilva/MJL
TIDES/COASTAL FLOODING...