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000
FXUS61 KPHI 161007
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
607 AM EDT Tue Apr 16 2024

.SYNOPSIS...
High pressure builds in early this morning and lingers through the
remainder of the day, before a series of fronts and low pressure
systems affect the East Coast Wednesday through the end of the week.
High pressure looks to return to end the weekend and start the new
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
For the day today, upper level ridging will move in to our
north and west as a surface high moves southeast from the Great
Lakes. Fair weather is expected with a mostly sunny sky. High
temperatures will be a little above average with highs in the
upper 60s to low 70s for most spots. It will be a dry airmass
too with dew points generally in the 30s except near 40 over
Delmarva. These numbers were actually lowered some from the
forecast made yesterday afternoon. A sea breeze should develop
with a wind more from the south closer to the coast in the
afternoon.

Upper level ridging will slide eastward toward our region tonight.
This should limit coverage of showers despite a warm front
approaching from the south which will bring some increasing clouds.
We do keep just a slight chance of showers in the forecast towards
dawn though over the eastern MD shore but otherwise POPs are below
15 percent. Expect lows mainly in the upper 40s to low 50s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The short term forecast remains largely unchanged. 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.

By Thursday night, the weak coastal low will be shunted
southward enough that surface high pressure can build in and
briefly shutoff the chances for showers. Lows Thursday night
look to fall into the 40s most everywhere across the region.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Following the brief respite from showers Thursday night, the
next mid-level wave approaches the region on Friday. This wave will
bring yet another cold front across the region with the
opportunity for more showers. As of now, the front looks to
cross the region Friday night into Saturday so the highest PoPs
(generally 40-50 percent) of the long term period are in this
time frame. Following this, a reinforcing front may arrive later
on Saturday so chances for showers remain in the forecast to
start the weekend. Temperatures overall will be around normal
with highs mainly in the 60s and lows in the 40s.

To start the new week, high pressure may get a bit of an
extended stay (at least in comparison to what we are expecting
for the rest of the current week). Some long range guidance is
suggesting that a system may slide by just to our south on
Sunday or Monday so unfortunately, chances for a few more
showers can`t be ruled out completely just yet. Temperatures
remain near normal to start the new week.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Today...VFR. Locally light and variable winds early, then generally
northwest winds around 10 knots with a gradually backing trend
through the afternoon. A sea breeze may result in a more southerly
wind mostly at KACY in the afternoon. Moderate confidence.

Tonight...Increasing mid/high cloud cover but remaining VFR. Winds
becoming light and variable in the evening and then generally E/NE
overnight but remaining around 5 knots or less. Moderate
confidence.

Outlook...

Wednesday through Thursday...Sub-VFR conditions likely (70-80
percent) at times due to stratus and showers. The most likely time
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 (30 percent) especially Friday night.

&&

.MARINE...
Sub Small Craft Advisory conditions for today and tonight. For
today northerly winds around 10 knots early in the day veering
to east, southeast and eventually southerly through this
afternoon. Winds diminish to around 5 knots or less tonight.
Seas generally around 3 to 4 feet today diminishing to 2 to 3
feet tonight.

Outlook...

Wednesday...Sub-Small Craft Advisory conditions expected.

Thursday through Friday...SCA conditions possible (30-40 percent)
beginning early Thursday morning, mainly due to building seas. SCA-
level gusts also possible over our northern Atlantic Ocean coastal
waters.

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

&&

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

&&

$$

SYNOPSIS...AKL
NEAR TERM...Fitzsimmons
SHORT TERM...AKL/Fitzsimmons/MJL
LONG TERM...AKL
AVIATION...AKL/Fitzsimmons
MARINE...AKL/Fitzsimmons