903
FXUS61 KPHI 180134
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
934 PM EDT Sat May 17 2025

.SYNOPSIS...
Spotty showers, thunderstorms and warm weather persists through
this evening. A cold front will cross through the area tonight
followed by a secondary cold front on Sunday night. High
pressure will return for Monday and Tuesday. Another dynamic
weather system will approach the region towards the middle of
the week, bringing another period of unsettled weather through
the end of the week.

&&

.NEAR TERM /THROUGH SUNDAY/...
935 PM update...
Cold front currently bisects the region and is crossing
Philadelphia as I write this. Decent puff of wind with the front
with some gusts of 30-35 kts, but it should be relatively brief.
Showers continue trying to move into the region but are
generally dissipating as earlier expected as they approach I-95.
Also noticed a new shower pop up just off the coast, and that
could continue southward as the evening wears on, but overall,
forecast is on track. No notable changes at this juncture
compared to the last update.

715 PM update...
Showers and isolated storms are proving more persistent as they
move in from the west with the approaching cold front, so have
boosted POPs across the region, particularly the Poconos but
also NW NJ and the Lehigh Valley. Still think any showers
struggle to make it to I-95 corridor but a few sprinkles
wouldn`t shock me. Otherwise boosted winds for Sunday up with
gust on land up to 40 mph, and added some low chance pops in the
northwest closer to the upper low and northwesterly flow.

113 PM discussion...
A mix of sun and clouds continues for this afternoon and into
this evening. A cold front moves in during the evening from the
west as a surface low pressure system moves east from Ontario
into Quebec while the associated upper level low lumbers across
the lower Great Lakes. Any showers or thunderstorms look limited
for the remainder of Saturday. There is still a marginal risk
for parts of mainly northern New Jersey for an isolated strong
to severe storm but this threat looks low. Winds do continue to
pick up through this evening out of the WSW with gusts at times
to 20 to 30 mph.

For tonight, both the surface and upper low pass by to our north as
they move into New England. Any leftover showers/storms diminish
after sunset as drier air continues to move in and also due to the
loss of daytime heating. It will be cooler than recent nights with
lows generally ranging from the low to mid 50s north to the low 60s
south.

Sunday is looking like the better half of the weekend as tranquil
weather returns with the upper trough moving farther east. The
second half of our weekend features a partly cloudy sky mainly dry
conditions and lower humidity. Perhaps an isolated shower is
possible north and west, but general thinking is most of the area
will stay dry. The one thing to note is winds will increase as
diurnal mixing occurs as the area lies wedged between systems
resulting in a tightening pressure gradient. WNW winds will gust up
to around 30 mph at times.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
The upper level low over the Northeast US will move east into the
North Atlantic on Monday. This will give way to northwest flow as a
subtle mid-level ridge moves into the Ohio Valley on Tuesday. At the
surface, a secondary cold front crosses through the region early
Sunday night with high pressure over Canada extending its ridging
southward through Tuesday.

All in all, a benign weather period is anticipated across the Mid-
Atlantic region through Tuesday. Mostly clear skies and dry weather
is expected. Winds will remain a bit breezy Sunday night into Monday
with gusts up to 30 mph as the pressure gradient remains modest in
combination with downsloping northwest flow. Lighter winds are
expected for Monday night and Tuesday. Highs will mostly be in the
70s on Monday with a mix of 60s/70s on Tuesday. Lows will be in the
40s/50s at night.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
By Tuesday night and through the middle of the week, our attention
turns to our next weather system which will take aim at the area. A
deep upper trough is expected to close off over the northern Great
Lakes region on Wednesday. This feature is then forecast to gain a
negative tilt as a vigorous piece of energy rounds the base of the
trough Wednesday night into Thursday. The upper low will then
meander over the Northeast US through Friday.

Global and ensemble guidance continues to develop an area of low
pressure at the surface over the Ohio Valley while tracking up into
the eastern Great Lakes on Wednesday. As it does so, a secondary
coastal low will develop off the Mid-Atlantic coast by Wednesday
night while deepening as it moves up into New England on Thursday.
These features support another period of active and unsettled
weather with periods of rain starting as early as Tuesday night. For
now the heaviest rain looks to hold off until Wednesday and Thursday
where rain may be heavy at times. This potential is still quite a
few days out, so have continued to keep the forecast in line with
NBM guidance. PoPs have increased over the last 24 hours however,
now yielding roughly a 50-80% chance of rain on Wednesday and
Thursday. Shower chances decrease a bit Thursday night into Friday,
but still remain around 30-50% as the area remains situated under
the upper trough. Below normal temperatures are expected throughout
the period.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR. A shower may reach KABE and KRDG this evening,
resulting in brief reductions. Winds W to WNW around 10 kts with
a few gusts up to 20 kts, though a brief burst of gusts up to
around 30 kts are accompanying the cold front late this
evening. Moderate confidence.

Sunday...VFR. Winds increase out of the WNW in the morning,
ranging from 15-20 knots with gusts to around 35 knots. Moderate
confidence.

Outlook...

Sunday night through Tuesday...VFR. Occasional wind gusts up to
25-30 kt possible through Monday, otherwise no significant
weather expected.

Tuesday night through Thursday...Sub-VFR conditions probable
with rain showers likely.

&&

.MARINE...
Sub SCA conditions continue through tonight, though a few gusts
up to 30 kts possible with passing cold front late this evening.

For Sunday, a Small Craft Advisory is in effect for west winds
around 15 to 20 gusting up to 30 knots.

Outlook...

Sunday night...SCA due to wind gusts up to 25 kt.

Monday...Lingering SCA possible early due to gusts up to 25 kt,
diminishing to 15-20 kt late.

Monday night through Tuesday night...No marine headlines
expected.

Wednesday and Thursday...SCA conditions probable due to wind
gusts around 25 kt and seas building to 4-6 feet.

Rip Currents...

Have upgraded the risk of rip currents to moderate for the
Central and South Jersey Shore for Sunday. Otherwise, for the
northern Jersey Shore and the Delaware Beaches, the risk is low
tomorrow. Expect a low risk everywhere on Monday.

&&

.TIDES/COASTAL FLOODING...
Spotty minor coastal flooding is possible with Sunday morning`s
high tide as well within the tidal Delaware River at Burlington
and Philadelphia, but should fall short of advisory levels.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 6 AM Sunday to 6 AM EDT Monday for
     ANZ430-431-450>455.

&&

$$

SYNOPSIS...DeSilva
NEAR TERM...Fitzsimmons/Guzzo/RCM
SHORT TERM...DeSilva/MJL
LONG TERM...DeSilva/MJL
AVIATION...Guzzo/MJL/RCM
MARINE...Guzzo/Johnson/MJL
TIDES/COASTAL FLOODING...