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000
FXUS61 KPHI 161914
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
314 PM EDT Tue Apr 16 2024

.SYNOPSIS...
High pressure moves offshore tonight 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 WEDNESDAY NIGHT/...
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.

High pressure will continue sliding offshore Wednesday as a cutoff
low shifts over the Great Lakes and its cold front washes out across
the Mid Atlantic. Showers look to arrive across the I-95 corridor by
late morning/early afternoon timeframe with increasing chances
and coverage through the day. A cool onshore flow will help keep
an inversion in place for much of the day, limiting any
instability and, therefore, limiting thunderstorm development
during the afternoon hours. High temperatures will only reach
the low to mid 60s with the Poconos and immediate coastline
likely getting stuck in the mid to upper 50s.

Cold front moves through Wednesday night and brings with it
widespread showers and possibly a few thunderstorms. Any instability,
especially surface based instability, may remain limited
through this period, so it is uncertain how widespread the
coverage of storms will be. Lows will be in the upper 40s to mid
50s. Total rainfall amounts Wednesday and Wednesday night will
be around a half an inch or less.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
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 and
about 10 degrees below climo. 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. Light showers or
drizzle may linger through the day.

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.

High pressure will remain in control at least through Friday
morning before the next system arrives later in the day.
Temperatures will be closer to climo with upper 50s to low/mid
60s. The next mid-level wave approaches during the afternoon,
increasing shower chances into the evening.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Low pressure continues to work through the region Friday night, and
then the cold front follows through on Saturday. Best chances for
showers will be Friday night, and then any showers taper off
Saturday morning. Due to the scattered nature of these showers, will
keep PoPs capped at chance Friday night for now.

High pressure builds in from the north and west. Meanwhile, the cold
front will sag south of the Mid-Atlantic and will become nearly
stationary over the Southeast U.S., extending back through the Gulf
Coast states and into the Southern Plains.

Several waves of low pressure will develop on that boundary, but the
boundary should remain too far south for rain to affect the local
area. Best chances for any showers look to be Tuesday.

Temperatures will be several degrees below normal, with highs
generally in the low to mid 60s and lows generally in the 30s and
40s.

&&

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

Rest of today...VFR. Northwest winds gusting to 15-20 kts. A
sea breeze may result in a more southerly wind mostly at KACY in
the afternoon. High 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. High
confidence.

Wednesday...VFR in the morning before MVFR conditions arrive
through the afternoon as showers advance west to east. East-
southeast winds around 10 knots. Moderate confidence.

Outlook...

Wednesday night 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 Sunday...VFR, but a brief period of sub-
VFR is possible (30 percent) Friday night through Saturday
morning.

&&

.MARINE...
Sub-advisory conditions expected through Wednesday. Light south
winds tonight shift east-southeast during the day Wednesday.
Seas 2-3 feet.

Outlook...

Wednesday night through Friday...SCA conditions possible beginning
early Thursday morning, mainly due to gusty east-northeast winds
from a backdoor front and building seas. Greatest chances for
SCA conditions across the northern Atlantic waters.

Friday night through Sunday...Potential for SCA conditions Saturday
afternoon and evening, otherwise, sub-SCA conditions.

&&

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

&&

$$

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