306
FXUS61 KPHI 171349
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
949 AM EDT Sat May 17 2025

.SYNOPSIS...
Spotty showers, thunderstorms and warm weather persists through this
afternoon. A cold front will cross through the area later today
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/...
950 AM...No major changes to the forecast.

The threat for severe weather today continues to diminish. The
Storm Prediction Center has removed most of the area from the
MARGINAL risk for severe thunderstorms with the exception being
portions of coastal and northern NJ. However even for these
areas that remain in the marginal the threat for severe weather
looks low. As of early this morning, a piece of energy aloft
moving around the large upper low near the Great Lakes is
pushing some more scattered showers and isolated storms towards
the region as it moves in from the west. But this has weakened
considerably over the past few hours so at this point it`s
looking like it won`t do much more than bring the area some
scattered showers with the chance of some isolated storms as it
moves through this morning into the early afternoon. After this
time we`ll have have an initial weak cold front (really more of
a dry line) moving through in the afternoon followed by a
stronger cold front in the evening. This will occur as surface
low pressure moves east from Ontario into Quebec while the
associated upper level low lumbers across the lower Great Lakes.
At this point though, any additional isolated to scattered
showers/storms PM looks to be quite limited. Otherwise expect a
mix of sun and clouds with highs generally in the 80s and
falling humidity levels in the afternoon. It will also become
fairly breezy with WSW winds gusting 20 to 30 mph.

For tonight, both the surface and upper low pass by to our
north as they move into New England. Any left over
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. Partly to
mostly cloudy skies are expected with dry conditions and low
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. West wind gusts up 30-35 mph will be possible.

&&

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

Today...Patchy fog and low stratus around early this morning
will bring some localized restrictions to IFR in spots. There
will also be some scattered showers with the risk of isolated
thunder moving through this morning into the early afternoon
which could bring brief restrictions if it hits a TAF site.
Otherwise VFR today. Winds increasing out of the WSW to around
10-15 kts with gusts to around 25 kts by this afternoon.
Moderate confidence.

Tonight...VFR. Winds W to WNW 10 kts or less.

Outlook...

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

Tuesday night through Wednesday...Sub-VFR conditions probable,
especially on Wednesday with rain showers likely.

&&

.MARINE...
There are some storms moving over our southern waters early this
morning and these could bring locally strong wind gusts, hail,
and vsby restrictions due to heavy rain. The chance for some
scattered showers and isolated storms will linger for today over
the waters but otherwise but otherwise the winds and seas stay
below SCA levels today outside of any storms. Sub SCA conditions
continue tonight.

For Sunday, a Small Craft Advisory is in effect for west winds
around 15 to 20 gusting up to 25 knots.

Outlook...

Sunday night...Lingering SCA conditions possible due to wind gusts
up to 25 kt.

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

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

Rip Currents...

Currently still projecting low risk of rip currents through the
weekend based on low wave heights of 1-2 feet and winds
shifting offshore at 10-15 mph.

&&

.TIDES/COASTAL FLOODING...
A Coastal Flood Advisory for northwestern Burlington and lower
Bucks Counties remains in effect until 8 AM today.

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 to 8 PM EDT Sunday for ANZ430-
     431-450>455.

&&

$$

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