-- Discussion containing changed information from previous version are highlighted. --
638
FXUS61 KPHI 062304
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
704 PM EDT Mon May 6 2024

.SYNOPSIS...
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A cold front will work its way through the region tonight before
becoming nearly stationary south of Delmarva. Low pressure tracks
along the front late tonight through Tuesday morning. Another area
of low pressure passes through the region on Wednesday followed by a
stronger low on Thursday. A cold front passes through on Friday,
then several disturbances are possible this weekend.
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&&

.NEAR TERM /THROUGH TUESDAY/...
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As of 700 PM, a weak cold front is across northwest New Jersey, the
Poconos then trails southwestward. The lower cloud cover is tending
to thin/clear in the vicinity of this front with just some mid to
high level clouds from the southwest. Farther south, lower clouds
remain however the cloud bases have come up some overall. Given
these trends, significantly adjusted the PoPs to remove them across
the north and delayed the increase some across Delmarva. A decent
amount of convection is ongoing in Virginia and it is slowly moving
east-northeastward. At least some of this is expected to slide
across our Delmarva zones later this evening and overnight and also
get into far southern New Jersey. North of here, little to no shower
activity may occur. Made some tweaks to the hourly temperature and
dew point grids to keep them current based on the latest
observations, and adjusted the cloud cover down across the northwest
areas some for a time given satellite trends.

Otherwise, a cold front will slowly slide south across the area
tonight and with a weak wave of low pressure track along it the best
best forcing for ascent and RH is across the southern areas (highest
PoPs will be here for the overnight). Some instability may result in
a thunderstorm. As for rainfall, around a quarter inch can be
anticipated down around far southern New Jersey and Delmarva.

As the cold front settles through the area, some drying is forecast
from the north and this is most notable across the northern portions
of our coverage area. Given the lack of wind and therefore mixing
overnight with the front, some fog is expected. There may be enough
drying though to prevent widespread fog coverage or dense fog and
given the uncertainty just included patchy fog for now. Overnight
lows will be in the lower 50s to lower 60s.

Weak low pressure will be just east of Delaware Tuesday morning.
This will keep showers and isolated thunderstorms in the forecast
through at least the daybreak hours. Showers and possibly a few
thunderstorms are expected to decrease by lunchtime as low pressure
moves offshore. PoPs won`t be zero for the remainder of the day for
all areas, but the most showers should be in the morning. Afternoon
highs will be in the 70s.

Another area of low pressure will track from the Great Lakes into
the Ohio Valley. A warm front extending out from that system will
lift towards southwest portions of the area later in the day.
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&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
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Another area of low pressure will track from the Great Lakes into
the Ohio Valley. A warm front extending out from that system will
lift towards southwest portions of the forecast area Tuesday night.
Scattered showers and thunderstorms will develop in the evening and
then become likely for most of the region after midnight Tuesday
night and into Wednesday morning as that warm front lifts through
the region. Precipitation tapers off by midday Wednesday, and then a
warm and humid airmass will be in place. Highs top off in the mid to
upper 80s, except for the low 80s in the southern Poconos and
northern New Jersey, and in the 70s along the coasts. Surface dew
points will be in the upper 50s to low 60s in the afternoon.

Low pressure approaches from the west Wednesday night, and scattered
showers and isolated thunderstorms will move into portions of
southeast Pennsylvania and Delmarva late Wednesday night. As the
main surface low tracks towards western New York and
Pennsylvania, a secondary low will develop out ahead of this
primary low, resulting in more widespread showers with
scattered thunderstorms moving into the region Thursday
afternoon and evening as a warm front lifts north of the region.
Global guidance has indicated some instability as the warm
front lifts north, suggesting the potential for some strong to
severe thunderstorms south of the warm front during the
afternoon, but exactly how far north the warm front progresses
will greatly determine the coverage of any strong to severe
storms in our forecast area. At the moment, it remains too
uncertain to mention anything more specific at this time. Even
the afternoon high temperatures will be highly variant on where
the warm front ends up, with low to mid 60s north of the front
and mid to upper 70s south. Showers and storms will taper off
Thursday night as the storm system shifts offshore.
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&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A cold front will push through the region Friday afternoon and
evening. Yet another round of scattered showers and isolated
thunderstorms will affect the area during that time.

Behind the cold front, surface high pressure builds east.
Several weak disturbances may touch off some afternoon showers
on Saturday and Sunday.

Highs will then be in the 60s for southeast Pennsylvania and
New Jersey and in the low to mid 70s in Delmarva on Friday.
Below normal highs expected for Saturday and Sunday, generally
in the low to mid 60s.

&&

.AVIATION /23Z MONDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...A blend of MVFR/VFR conditions this evening are expected
to lower to MVFR and IFR overnight (locally LIFR possible). Some fog
is expected overnight. Some showers overnight mainly at KMIV and
KACY. West-southwest to northwest winds 3-5 knots becoming mostly
light and variable to locally calm. Low confidence on how widespread
the fog will become.

Tuesday...Areas of MVFR/IFR for a time in the morning, then
conditions improve to VFR. Some mainly morning showers mainly near
KACY and KMIV. Light and variable winds, becoming east-northeast to
east-southeast around 5 knots then becoming locally southwest in the
afternoon. Low confidence on timing details when conditions return
to VFR and also wind shift details given light speeds.

Outlook...

Tuesday night through Saturday...Sub-VFR conditions at night in
fog and stratus, while VFR conditions overall during the day.
Chances for SHRA/TSRA throughout the period with sub-VFR
conditions. More widespread SHRA with scattered TSRA Thursday
afternoon and evening.
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&&

.MARINE...
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Tonight through Tuesday...The conditions are expected to remain
below Small Craft Advisory criteria. Some fog, possibly dense,
improving during Tuesday.

Outlook...

Tuesday night through Saturday...Overall, sub-SCA conditions
through the period. Scattered showers and thunderstorms will
result in locally higher wind gusts and seas, with biggest
impacts coming on Thursday afternoon and evening.
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&&

.TIDES/COASTAL FLOODING...
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Tidal ranges increasing this week as the new moon arrives Tuesday
evening. Limited onshore flow means that there won`t be much in
the way of serious flooding concerns, but still minor tidal
flooding is possible beginning tomorrow evening and perhaps
Wed/Thu evening as well. A Coastal Flood Advisory may be issued
overnight if trends remain.
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&&

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

&&

$$

SYNOPSIS...MJL
NEAR TERM...Gorse/Kruzdlo
SHORT TERM...MJL/MPS
LONG TERM...MJL/MPS
AVIATION...Gorse/Kruzdlo/MJL
MARINE...Gorse/Kruzdlo/MJL
TIDES/COASTAL FLOODING...O`Hara