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000
FXUS61 KPHI 152317
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
717 PM EDT Mon Apr 15 2024

.SYNOPSIS...
A cold front will settle south and east of our area tonight.
High pressure builds in later tonight and lingers through
Tuesday, before a series of fronts and low pressure systems
affect the East Coast Wednesday through early this upcoming
weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 715 PM, a cold front looks to be in the process of
crossing the I-95 corridor. This front will continue to settle
south and eastward this evening with a wind shift to the
northwest in its wake. Drier air will also be filtering in
through the overnight. Ahead of this front, a few showers or a
thunderstorm are around in parts of mainly southern New Jersey
into Delmarva. The coverage has decreased and therefore sped up
the lowering of the PoPs some. A sea breeze has works its way
inland some across southern New Jersey and also across Delaware.

As we go through tonight, the sky will become clear across the
the region. The overnight lows will drop to the low/mid 40s for
the N/W areas and only fall into the low 50s for south NJ and
Delmarva.

On Tuesday, upper ridging will continue over the area as a surface
high moves southeast from the Great Lakes. Fair weather is expected
with mostly sunny skies expected. high temperatures will be a little
above normal with highs in the upper 60s to low 70s for most spots.
A decently dry airmass too with dew points in the upper 30s/low 40s.
Winds will be mostly West at 5 to 10 mph.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Upper level ridging will slide eastward toward our region
Tuesday night. This should limit coverage of showers despite a
warm front approaching from the south. Lows in the upper 40s to
low 50s.

On Wednesday, the shortwave ridge weakens ahead of the next
closed low approaching from the west, leading to increasing
chances for showers though the day. Thanks in large part to the
warm front in the region, there will likely be a robust
temperature inversion through the day, resulting in limited
instability. Therefore, not expecting any thunderstorms at this
time. Daytime highs will only be in the low to mid 60s.

The closed low and a trailing cold front approach the region
Wednesday night into Thursday. Consequently, there are chances
for widespread showers and thunderstorms in the Wednesday
night/Thursday period. As far as thunderstorms, instability,
especially surface based instability may remain limited through
this period, so it is uncertain how widespread the coverage of
storms will be. At this point, it appears as if we are likely to
have widespread showers with some embedded thunderstorms,
primarily late Wednesday night into Thursday morning, though
there still remains quite a bit of uncertainty with the timing.

For the rest of the day Thursday, global guidance is showing the
potential for a backdoor front arriving as high pressure off the
coast of Maine interacts with a weak coastal low off the
Delmarva seaboard that will spin off from the decaying parent
cold front from the previous night. Resultant E to NE flow will
help keep temperatures much cooler than earlier in the week.
Depending on how far south this backdoor front advances,
temperatures to the north will be in the 50s with mid to upper
60s to the south.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Tranquil weather should return again, albeit briefly, as the low
departs our region Thursday night into Friday, before the next cold
front approaches to start the weekend. At this point, the forecast
has rain chances almost throughout this period (Friday night through
Sunday), but it is unlikely to be a washout through the period,
rather there remains uncertainty in the exact timing of the cold
front. Once the cold front passes, we should have drying conditions.

&&

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

Tonight...A few showers or a thunderstorm around early in the
vicinity of KACY and KMIV, otherwise VFR. Southwest winds
5-10 knots becoming northwest to north. Some terminals should
have the wind go light and variable. Moderate confidence.

Tuesday...VFR. Locally light and variable winds early, then north-
northwest winds around 10 knots becoming west to southwest later
in the day. Moderate confidence.

Outlook...

Tuesday night...VFR.

Wednesday through Thursday...There is a chance (50 to 60
percent) for sub-VFR conditions at times due to stratus and
showers. The best chances for this looks to be overnight
Wednesday night into Thursday morning.

Thursday night through Saturday...VFR, but a brief period of
sub-VFR is possible (20 percent) especially Friday.

&&

.MARINE...
A shower or thunderstorm around early this evening. Otherwise,
winds and seas will remain below SCA levels through Tuesday.

Outlook...

Tuesday night through Wednesday...Winds and seas should stay
below SCA criteria.

Wednesday night through Friday...SCA conditions possible for at
especially over our northern ocean zones as winds and seas build.

Friday night through Saturday...Sub-SCA conditions.

&&

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

&&

$$

SYNOPSIS...Fitzsimmons/MJL
NEAR TERM...Gorse/OHara
SHORT TERM...Fitzsimmons/MJL
LONG TERM...Fitzsimmons/MJL
AVIATION...Gorse/MJL/OHara
MARINE...MJL/OHara