109
FXUS61 KPHI 231849
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
249 PM EDT Thu May 23 2024

.SYNOPSIS...
A cold front move across the area this evening. The front will stall
to our south on Friday before lifting back north on Friday night as
a warm front. Another cold front moves through on Sunday with a
stronger system impacting the area on Monday into Tuesday. A
secondary cold front looks to cross the area on Wednesday into
Thursday.

&&

.NEAR TERM /THROUGH FRIDAY/...
A closed low centered just north of the Great Lakes will shift
eastward through Friday. Surface low pressure tied to this feature
will pull a weak cold front across much of our area through tonight.
A surface trough remains across our area and this will either shift
east into this evening or be absorbed by the incoming weak cold
front. The flow aloft does become more cyclonic late tonight into
Friday morning as the southern portion of the closed low amplifies a
bit more southward.

In the wake of a convectively enhanced shortwave that brought quite
a bit of convection early this morning to eastern Pennsylvania and
New Jersey has slowed the boundary layer heating some. A north to
northwest wind occurred behind this feature with a little drying as
well. The air mass is in the process of recovering and there is
enough instability for some thunderstorms to redevelop. The
instability should increase some into this evening as some clearing
takes place. There is another convectively enhanced or generated
shortwave/MCV moving across southern West Virginia and this feature
will move east-northeastward. The chance for additional convection
across the northern areas has decreased as these areas will see more
drying sooner with less instability and weaker forcing. Farther
south has the greater chance for some scattered showers and
thunderstorms through this evening, especially if an area of
enhanced forcing arrives from the aforementioned MCV. There is
enough shear and instability in place which could result in isolated
severe thunderstorms with locally damaging wind gusts the main
threat. The coverage overall looks to be isolated to scattered
especially from about the Philadelphia metro on south and east. The
convection should tend to wane overnight, however a trailing
shortwave may result in some showers or thunderstorms early Friday
morning for Delmarva, southern New Jersey and perhaps into parts of
southeast Pennsylvania. The wind will be light to calm tonight and
if clouds clear enough for a time, patchy fog will be possible.

As we go through Friday, a weak cold front should be stalling across
parts of Delmarva. The placement of this front along with a trailing
piece of energy may continue to support some showers or thunder
across our southern areas to start the morning. The cloud cover will
clearing from the northwest, with some mid to high level clouds
lingering the longest for our Delmarva to southeastern New Jersey
areas. As the low-level flow turns more westerly in the wake of the
front, drier air will arrive and dew points are forecast to drop
into the 50s for much of the area. The dew points look to remain in
the 60s however across Delmarva to southeastern New Jersey. It will
be a warm day with much of the area getting into the 80s, although
with lighter flow expected a sea breeze should develop resulting in
cooling closer to the coast.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
Tranquil weather will continue into Friday night with clear skies
and light winds initially. We should be able to radiate pretty well
leading to some patchy fog development over Delmarva and southern
New Jersey. However, clouds will increase from south to north later
in the night as the stalled front begins to lift back north across
the area. This should limit the amount of cooling late, so expecting
lows in the mid 50s to lower 60s.

For Saturday, the warm front will lift completely north of the area
as the main low pressure system tracks across the Great Lakes.
Saturday morning 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 should hold
off entirely until Saturday evening, although it will be a mix of
sun and clouds most of the day. This system will be a rather quick
mover so while Saturday night does appear to be wet especially north
and west, all precipitation should end by Sunday morning. The region
should dry out on Sunday as the front now looks to stall to our
north and west, resulting in sunny skies in the afternoon with some
fair weather clouds. Slight chance of a shower in the higher
elevations which remains closer to the stalled boundary. Aided by
warm air advection, highs on Saturday and Sunday should reach into
the low to mid 80s with cooler temps along the coast. Saturday night
lows will be in the mid 50s to low 60s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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 Marginal risk
for Excessive Rainfall and CIPS analog guidance is highlighting the
potential for severe weather across the Delmarva (10-15% chance) on
Monday and across the entire area on Tuesday (10% chance). 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
70s through Wednesday, before falling back into the 60s by
Thursday.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Rest of this afternoon...VFR overall, however a few showers or
thunderstorms will be around especially from around the KPHL area
south and eastward. Locally and brief sub-VFR conditions will occur
with any shower/thunderstorm. West to southwest winds mostly 5-10
knots. Low confidence.

Tonight...VFR overall, however a few showers and thunderstorms will
be around this evening which can result in local and brief sub-VFR
conditions. Localized fog cannot be ruled out overnight. Winds
becoming light and variable to calm overall. Low confidence.

Friday...VFR overall. A few showers or a thunderstorm possible early
in the morning. Light and variable winds becoming northwest around 5
knots, then becoming west. A sea breeze may result in winds becoming
south or southeast at KACY and KILG in the afternoon. Moderate
confidence.

Outlook...

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 Tuesday...Sub-VFR conditions probable with a
chance of showers and thunderstorms especially on Monday into
Monday night.

&&

.MARINE...
The conditions are expected to remain below Small Craft Advisory
criteria through Friday, however a few gusty thunderstorms will be
possible this evening mainly across the southern coastal waters
including Delaware Bay.

Outlook...

Friday night through Tuesday...No marine headlines expected. Winds
will occasionally gust up to 15-20 kt with seas around 2-4 feet. A
chance for showers is expected on Saturday night with a chance for
showers and thunderstorms Monday into Tuesday. Marine fog is also
possible on Saturday morning.

Rip Currents...

S to SW winds will average 5 to 10 mph today along with
breaking waves around 2 feet. There is a LOW risk for the
development of dangerous rip currents at NJ and DE beaches for
today. However, some showers and thunderstorms will be around.

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 rip currents at NJ and DE
beaches. 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
occurring today, 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...Gorse
SHORT TERM...Deal/DeSilva
LONG TERM...Deal/DeSilva
AVIATION...DeSilva/Gorse
MARINE...DeSilva/Gorse
TIDES/COASTAL FLOODING...WFO PHI