717
FXUS61 KPHI 151514
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1114 AM EDT Wed May 15 2024

.SYNOPSIS...
Several waves of low pressure will slowly pass by the area through
tonight. These waves will consolidate into one low pressure that
meanders offshore on Thursday. Weak high pressure briefly builds
into the region Thursday night and Friday. Another slow moving low
pressure system will cause unsettled conditions through the weekend
lingering potentially into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
950 AM...As of mid morning, low pressure was located near the
mouth of the Chesapeake Bay and will slowly meander from there
northward into tonight. Although it will only slightly
strengthen, it will still produce a widespread rainfall across
the forecast area. The rain will be over much of the area today
and then be more focused closer to the New Jersey coast this
evening and tonight. Forecast rainfall totals have increased
over the next 24 hours. We are forecasting storm totals of
about 0.25 inches well north and west to about an inch south and
east.

Highs today were lowered slightly with the mid morning update
and are generally forecast to be in the low 60s. Lows tonight
will be in the 50s.

Mainly a southeast/east wind to start the day. We`ll finish the
forecast period with northeast winds. We`re expecting the winds to
be noticeable today into tonight gusting up to 20 or 25 mph.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Coastal low pressure will meander off the Mid-Atlantic coast on
Thursday as the waves of low pressure merge into one system. The low
then drifts east into the western Atlantic on Friday. Weak high
pressure also approaches on Thursday, but it doesn`t really build
fully into the region until Thursday night and Friday.

Thursday will consist of periods of light rain being thrown back
around the northern side of the low primarily across Delaware, New
Jersey and the Poconos. To the south and west, dry air will begin to
filter in from the approaching high which will allow PoPs to be less
across southeast Pennsylvania and eastern Maryland. However, with
the low still in relative close proximity to the area, low clouds
and stratus will likely be difficult to erode. Some breaks will be
found the further west you are, but with onshore flow, it will feel
quite damp and cool. Highs on Thursday will be in the 60s areawide.

Thursday night will feature drying conditions across the area with
just some lingering showers near the coast. Decreasing clouds
overnight with lows in the 50s. Friday at this point looks like the
"pick of the week" considering the entire forecast. Surface high
pressure will be in control causing a mix of sun and clouds along
with seasonable temps in the upper 60s to mid 70s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The long term period continues to remain highly variable due to the
timing differences amongst forecast guidance with regards to the
next low pressure system.

The surface high over the region on Friday will retreat to the
northeast on Friday night. Another slow moving low pressure system
will move along the southern Appalachians on Saturday, over the Mid-
Atlantic on Sunday, and eventually offshore into early next week.
The biggest forecast challenge at this point is the timing of the
system as it works its way across the area though. Guidance
continues to struggle and vary from run to run. To avoid a
windshield wiper effect to the forecast, have continued to base the
long term forecast strictly off the NBM. This generally includes a
slight chance of rain showers Friday night, increasing and peaking
on Saturday into Saturday night before decreasing on Sunday. For
now, it still looks like the weekend will be fairly unsettled, but
it may not entirely be raining the entire time. Precip chances
reduce on Monday and Tuesday as the low exits the region. Temps are
expected to be below average for Saturday and Sunday, before making
a return closer to average on Monday and Tuesday depending on the
progression of the low.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Today...A mix of MVFR and IFR conditions in rain...becoming IFR. SE
winds 5 to 10 kts becoming NE around 10 to 15 kts with gusts up to
20 or 25 kts. LLWS concerns arise late this morning and persist
through the afternoon near the NJ coast where the center of the low
will track. High confidence with the MVFR, lower confidence on the
extent and duration of IFR conditions.

Tonight...MVFR and IFR in the evening becoming MVFR. Rain likely
across the I95 terminals and eastward. A chance of rain at KRDG and
KABE. Decreasing chances of rain as we move through the overnight. N
to NE winds 10 to 15 kts gusting to 20 or 25 kts. Moderate
confidence.

Outlook...

Thursday...Sub-VFR conditions continue with periods of light rain.

Thursday night through Friday night...Sub-VFR conditions possible on
Thursday night, improving to VFR on Friday. No significant weather
expected.

Saturday through Sunday...Sub-VFR conditions return with periods of
rain.

&&

.MARINE...
Today...As of mid morning, Gale force winds are occuring off the
coast of Delaware with this area of focused stronger east winds
moving northward as we go into this afternoon. A Gale Warning is
in effect until 1 PM for zones 454 and 455 and until 5 PM for
zones 451 and 452. SCA conditions today over zones 450 (off the
coast of Monmouth County) and the Delaware Bay.

Tonight...SCA conditions on our ocean waters. The SCA will also
continue on the lower Delaware Bay through at least the evening
hours. NE winds 15 to 25 kts. Seas 5-7 feet on the ocean.

Outlook...

Thursday through Friday...The SCA for all ocean waters is in
effect until 6 PM on Thursday. Due to elevated seas lingering
into Friday, the SCA will likely need to be extended. Conditions
will remain below SCA thresholds on the Delaware Bay.

Friday night through Saturday night...No marine headlines expected.

Sunday...Small Craft Advisory level conditions possible.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ430-
     431.
     Small Craft Advisory until 6 PM EDT Thursday for ANZ450.
     Gale Warning until 5 PM EDT this afternoon for ANZ451>453.
     Gale Warning until 1 PM EDT this afternoon for ANZ454-455.

&&

$$

SYNOPSIS...Desilva/MPS
NEAR TERM...Fitzsimmons/Kruzdlo
SHORT TERM...Desilva
LONG TERM...Desilva
AVIATION...Desilva/Fitzsimmons/Kruzdlo
MARINE...Desilva/Fitzsimmons/Kruzdlo