333
FXUS61 KPHI 141339
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
939 AM EDT Tue May 14 2024

.SYNOPSIS...
High pressure remains positioned offshore today. Unsettled weather
returns tonight and persists through Thursday as a slow moving low
pressure system passes by to our south. Weak high pressure returns
on Friday, before another period of unsettled weather impacts the
Mid-Atlantic region this weekend into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 930 am, temperatures across the region were in the low to
mid 60s. High clouds draped across the southern half of the
region continue to progress northward.

Increasing clouds can be expected to continue today with about
average afternoon highs, mainly in the mid 70s. Isolated to
scattered showers are possible this afternoon with the best
chances closest to sunset and mainly west of the I95 corridor.

The slower progression of the showers this afternoon along with
the chance of thunder across our western zones where CAPE
should be the greatest remains unchanged.

Winds today will be from the south to southwest in the 5 to 15 mph
range.

For tonight, showers become more widespread. I kept thunder in the
forecast into this evening, but took it out overnight. Clouds thicken
and lower, especially the second half of the night. Lows will be in
the 50s and winds will be out of the southeast at 5 to 10 mph.

Rainfall amounts across the region by Wednesday daybreak should
range from a few hundredths north to two to three tenths down over
the Delmarva.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
An upper trough near the Tennessee Valley on Wednesday will work its
way east over the Mid-Atlantic on Thursday and offshore by Thursday
night. At the surface, a weakening low over Tennessee will translate
its energy into a developing coastal low along the Carolinas on
Wednesday. This new low is then forecast to meander off the East
Coast through much of Thursday. However, the positioning of where
this low will track and eventually meander varies greatly between
broader-scale and hi-res model guidance. GFS/ECMWF guidance keeps
the low on a more coastal approach, whereas the NAM/HRRR and other
CAMs keep the low further south and east.

Regardless of the positioning of the low, our entire area is
forecast to remain on the northern side of the system. As a result,
onshore flow wrapping the low will result in frequent chances for
rain Wednesday and Thursday. Due to the southeast trend in short-
range guidance, have backed off on PoPs northwest of the I-95
corridor compared to previous forecast. The higher PoPs are now
found across the Delmarva and New Jersey which are in closer
proximity to the low. Have also removed the mention of thunder as
all instability will be found either well south of the area or
offshore.

The meandering low begins to pull away late Thursday allowing rain
chances to decrease into Thursday night as dry air begins to filter
in. However, shower chances will likely remain along the coast as
flow becomes northeast off the ocean. So while most areas dry out
Thursday night, there likely will still be some spotty shower
activity along the coast.

Highs on Wednesday and Thursday will mostly be in the 60s with some
70s possible northwest of I-95 on Thursday. Low temps are expected
to be in the mid to upper 50s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The long term period starts off quiet on Friday as upper ridge
builds overhead and temporary surface high moves by. This will
result in Friday being mostly dry. However, what happens after
Friday is quite uncertain as there is high variability in the timing
of the weekend system. At this point in time, the general consensus
for the some of the ensembles is for showers to return as early as
Friday night. However, this is completely different from the
majority of the GFS ensembles which delay the onset of precip until
late Saturday. Given the vast uncertainty and differences between
ensembles, the forecast is strictly basis the National Blend of
Models (NBM) for Friday night and beyond. This yields a chance of
showers and possibly a few thunderstorms during the weekend period.
Eventually, a cold front will sweep across the area and push any
shower activity offshore. This doesn`t look like it will happen
until at least Monday, so while most of the weekend does look to be
unsettled, it may not entirely be raining the entire time. Temps are
expected to be below average for Friday and Saturday, returning
closer to average by Sunday, and possibly above average into early
next week depending on the timing of features.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Today...VFR through most of the day. Widespread MVFR CIGs
developing between 21Z and 24z with the best chances west of the
I95 corridor. Isolated to scattered rain showers may result in
brief sub-VFR VSBYs as well. S winds 5 to 15 kt. Moderate
confidence.

Tonight...MVFR conditions likely with some IFR mixed in. Light SW
winds. Showers becoming more numerous. Moderate confidence.

Outlook...

Wednesday through Thursday...Sub-VFR conditions likely with periods
of light rain.

Thursday night through Friday...Anticipate VFR. No significant
weather expected.

Friday night through Saturday. Sub-VFR conditions likely return.
Occasional showers likely especially on Saturday.

&&

.MARINE...
Today...Sub-SCA conditions. South winds 10 to 20 kts. Seas 3 to 4 ft.

Tonight...Sub-SCA conditions. Southeast winds 10 to 15 kts. Seas 2
to 3 ft.

Outlook...

Wednesday...A Small Craft Advisory has been issued for the ocean
waters offshore Great Egg Inlet to Fenwick Island beginning at 10 AM
and beginning at 1 PM Wednesday for the ocean waters offshore
Manasquan Inlet to Great Egg Inlet. The northern ocean zone and
Delaware Bay are expected to remain below SCA thresholds.

Wednesday night through Friday night...SCA conditions likely
continue all ocean waters due to elevated seas around 5-7 feet.
Winds may briefly gust around 25 kt on Wednesday and Thursday as
well. Light rain expected Wednesday through Thursday night, before
fair weather on Friday.

Saturday...No marine headlines expected.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 1 PM to 6 PM EDT Wednesday for
     ANZ451-452.
     Small Craft Advisory from 10 AM to 6 PM EDT Wednesday for
     ANZ453>455.

&&

$$

SYNOPSIS...AKL/Desilva
NEAR TERM...AKL/Kruzdlo
SHORT TERM...Desilva
LONG TERM...Desilva
AVIATION...AKL/Desilva/Kruzdlo
MARINE...Desilva/Kruzdlo