573
FXUS61 KPHI 211721
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1221 PM EST Fri Nov 21 2025

.SYNOPSIS...
High pressure will shift offshore through Friday. Developing
low pressure will pass offshore late Friday night followed by
high pressure building into the region through early next week.
A strong frontal system looks to impact the region during the
middle to end of next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
High pressure over the area weakens as it slides offshore.
Several shortwaves will pass through the region through this
evening, and this will keep skies cloudy. Cloud bases may lift
this evening, and could even scatter out a bit.

Weak low pressure currently over Nebraska and Oklahoma will
track east through the Midwest and Ohio Valley tonight, and will
be near the Appalachians after midnight tonight. This low will
slowly work its way through the Mid-Atlantic and Delmarva
Peninsula Saturday morning. The low will then be some 200 miles
south and east of Nantucket Island by Saturday afternoon. Weak
upper level troughiness with strong shortwave energy passes
through the region late in the day as surface high pressure
builds in from the west.

Rain develops over the area late tonight and continues through
Saturday morning. Most of the rain will taper off around midday,
though some lingering rain may persist over the coastal areas
as the low departs. Conditions then improve late. Overall, can
expect 1/4 to 1/2 inch QPF throughout, though less than 1/4 inch
north of I-78 and closer to 1/2 inch over Delmarva.

Fairly mild for this time of the year with lows in the low to
mid 40s tonight, and then in the low to mid 50s on Saturday.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
Cooler and dry high pressure will settle in Saturday night through
Sunday. Lows Saturday night in the mid 20s to mid 30s and highs
Sunday mainly in the upper 40s to low 50s under mainly clear skies.
WSW winds 5-10 mph.

Sunday night will be a bit warmer compared to Saturday night as a
wave passes by to our north resulting in a little more wind and
mixing in the boundary layer. Generally expect lows in the 30s but
it will remain dry.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Overall seasonable conditions and benign weather expected to begin
next week followed by a warming trend Tuesday into Wednesday as the
next frontal system affects the area. A strong cold front then looks
to move through around Thanksgiving Day but there are some model
differences in the exact timing since this is almost a week out.

In terms of details, the week begins mainly clear for Monday as high
pressure will be centered over the area with seasonable temperatures
(highs mainly in the 50s). Heading into Tuesday, warm advection
strengthens ahead of the next system approaching from the Great
Lakes. This will lead to milder temperatures but also increasing
chances for rain by later in the day and especially at night (POPs
generally around 70 percent).

Heading into the middle to end of next week, differences in the
forecast models increase with regards to how quickly the
aformentioned system moves through. The GFS depicts a secondary
low developing near the triple point Wednesday night into
Thanksgiving Day which would keep periods of rain/shower around
longer but also delay the eventual arrival of much colder air.
Meanwhile the ECMWF and GEM favor a faster progression of the
cold front through the area along with the associated upper
level trough. This would result in drier but much colder weather
building in for Thanksgiving Day. Given this uncertainty we
stayed with the National Blend of models which keeps a 20-30
percent chance of rain going into the first part of Thursday
with highs generally forecast to be in the upper 40s to mid 50s.
It should be noted though that if the system is slower it will
be warmer and wetter (highs Thanksgiving Day in the 50s to low
60s) while if it`s faster it will be colder but dry (highs in
the 30s to low 40s). Regardless of these differences in FROPA
timing around Thanksgiving Day, the trend will be for much
colder air to eventually arrive by next Friday and persist
through Thanksgiving weekend.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of today...MVFR CIGs, with some improvements to VFR along
and east of the I-95 corridor terminals late. SW winds less than
10 kt. Low confidence.

Tonight...Any VFR CIGs will lower to MVFR/IFR by 04Z. RA
develops with MVFR/IFR VSBYs. LGT/VRB winds. Moderate
confidence.

Saturday...IFR in the morning, briefly lifting to MVFR, then to
VFR after 18Z. Light NE winds in the morning, becoming NW less
than 10 kt after 18Z. Moderate confidence.

Outlook...

Saturday night through Monday night...VFR. No significant
weather.

Tuesday...VFR to start, with sub-VFR conditions possible later
in the day in periods of light rain.

&&

.MARINE...
Conditions will remain below Small Craft Advisory criteria for
the rest of the day today, tonight, and Saturday.

Southwest winds 10 to 15 kt through this evening, becoming
light and variable late tonight. North winds pick up at 10 to 15
kt with gusts up to 20 kt late Saturday morning, backing to the
northwest late in the day.

Visibility restrictions in rain developing after midnight
tonight and continuing through most of Saturday.

Outlook...

Saturday night through Tuesday...No significant weather impacts
anticipated.

&&

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

&&

$$

SYNOPSIS...Fitzsimmons/Staarmann
NEAR TERM...MPS
SHORT TERM...Fitzsimmons/Staarmann
LONG TERM...Fitzsimmons
AVIATION...MPS
MARINE...MPS