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005
FXUS61 KPHI 240804
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
404 AM EDT Fri May 24 2024

.SYNOPSIS...
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A cold front will stall to our south today before lifting back
north this evening 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. High pressure looks to return
towards the end of the week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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A weak cold front lingering around the I-78 corridor will gradually
push south and east reaching near or just south of the I-95 corridor
by morning as it approaches Delmarva. A few showers and some
isolated rumbles of thunder will be possible over the next few hours
through daybreak as the front slowly shifts over SE PA into southern
NJ and the Delmarva(POPs 20 to 30 percent or less).

As we start off Friday, our weak cold front is forecast to stall
across parts of Delmarva. At the same time, shower/storm chances
increase over our southern zones as a mid-level shortwave arrives to
usher in a weak surface low trekking along the frontal boundary from
Virginia into the Delmarva. Showers with some isolated thunderstorms
will mainly impact the Delmarva region along with southern NJ and
extreme southeast PA during the morning hours.

Moving into the afternoon, this weak surface low will push offshore
as surface high pressure over the Great Lakes gradually builds in
from the north and west, bringing in a drier airmass. Temperatures
are expected to warm into the low to mid 80s for the Philly metro
area and points north where clearer skies are expected. Further
south where we will see the morning precipitation, cloud coverage
will slow daytime heating and likely limit the afternoon high
temperatures to the upper 70s to right around 80.

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 with mid 60s around
Philadelphia.
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&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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Saturday morning should be fairly quiet as some patchy fog sits
over DelMarVa early. That should lift and mix out with diurnal
heating in the boundary layer. A warm front will push north of
the area with the main forcing for some afternoon showers
occuring late in the day moreso over PA with the best chance for
precip generally over the Lehigh Valley and Poconos. With
guidance trending towards a weaker system the forecast no longer
calls for showers to make it to the shore which then pushes
temps up through the day. Temps are anticipated to again warm
into the mid 80s with low 70s along the shore.

Brief high pressure develops on Sunday with the front stalled
to the north of the region and it should be another pleasant day
across the region with sunny skies and fair weather CU
developing. Highs Sunday should also push into the mid 80s with
70s along the shore. Expect lows each night to fall into the 50s
to low 60s.
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&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
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The work week begins with a more unsettled pattern. Starting
Monday an upper level system will push a cold front through the
region. With warm air advection initially and strong PVA, there
will be ample lift associated with the system tapping into a
surge of PWAT from both the Gulf and the Carolinas. This leads
to widespread convection across the region and EL`s should be
sufficient to support thunderstorms. While CIPS guidance has
started to trend slightly down on the severe threat yesterday,
the 00z GEFS showed a significant increase back to a 10-15%
chance of severe weather on Monday. Bulk shear vectors point
towards 35-40kts with mid level lapse rates in the 6 degC/km.
This should provide enough forcing for some stronger storms to
become severe. WPC upgraded the Marginal from yesterday to a
Slight risk for portions of the I95 corridor and PA. Given that
SPORT LIS Soil Moisture data show dry conditions in the 10-40cm
depth range, anticipate that any flooding will most likely be
over the impervious surfaces of the more urban area rather than
over more rural areas. Given the increasing confidence in at
least heavy rain, the forecast was updated to include specific
mention of heavy rainfall for any locations where the precip
chances were higher than 55%.

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 work week should be fairly seasonable
with highs in the 70s through Wednesday, before falling back
into the 60s by Thursday.
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&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Early this morning (through 12Z)...VFR overall, though a rogue
shower may be possible. Some low stratus and mist/fog could develop
early morning that affects MIV and ACY, bringing sub VFR conditions.
Some showers and perhaps a thunderstorm will be possible for
ILG/MIV/ACY towards daybreak as well. Moderate confidence.

Today...VFR overall except some lingering mist/fog and stratus
likely to start the day at MIV and ACY. Also, a few showers or a
thunderstorm will be 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.

Tonight...Clear skies and calm winds to start will allow for
strong radiational cooling, but dew points are still expected to
be in the 60s across southern NJ and the Delmarva. Could see
some sub- VFR fog developing in that region as a result, mainly
impacting MIV/ACY. Otherwise, VFR conditions for terminals
further north and west.

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 strong thunderstorms especially on Monday
into Monday night.
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&&

.MARINE...
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The conditions are expected to remain below Small Craft Advisory
criteria through Friday night. Some isolated to scattered showers
and thunderstorms possible Friday morning across the southern marine
zones near the Delaware Bay and Delaware coastal waters. Light and
variable winds this morning become more SSW around 5-10 kts. Seas
remain around 2 feet.

Outlook...

Saturday through Tuesday...No marine headlines expected. Winds
will occasionally gust up to 15-20 kt with seas around 2-4 feet.
Marine fog could setup Saturday morning generally off the
Delaware coastline and over Delaware Bay. Showers and
thunderstorms are anticipated for Monday into Tuesday and could
bring strong to severe winds.

Rip Currents...

For today, 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.

The LOW risk for the development of dangerous rip currents is
expected to continue for Saturday.
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&&

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