602
FXUS66 KSEW 201037
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
237 AM PST Thu Nov 20 2025

.SYNOPSIS...
A splitting frontal system will maintain light showers across
western Washington this morning, with showers along the coast
throughout the day. High pressure will allow much of the region
to dry out on Friday and Saturday, with chances for additional
rain over the northern interior. A stronger system will bring
more substantial chances for rain and mountain snow across
western Washington Sunday into early next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
Light showers will continue across western Washington this
morning as a frontal system stalls and splits as it moves
inland. The bulk of the precipitation will taper off by the mid
morning, with showers continuing along the Pacific Coast into
the afternoon as onshore flow resumes. As high pressure builds
into the region later today, temperatures will warm up a few
degrees with highs reaching the low to mid 50s with plenty of
sun breaks. Along the Pacific Coast, large long-period swells
will arrive today, with potential for localized beach erosion
and significant wave run-up. While conditions are expected to
remain below High Surf thresholds, beachgoers are encouraged to
exercise caution and check the latest weather and water
conditions, and conditions across the coastal waters will
continue to be closely monitored.

The high pressure ridge will shift southward on Friday as the
jet stream strengthens over British Columbia. This will bring
renewed chances for rain across the northwestern portions of the
Olympic Peninsula and along the Canadian border, with dry and
cloudy conditions elsewhere. Temperatures will remain steady
with most lowland areas seeing highs in the lower 50s.

Saturday will bring more of the same, with light rainfall across
much of the region as the upper level jet shifts slightly to the
south. With snow levels lifting to 5000-6000 feet in the warm
sector of an approaching frontal system, snow accumulations will
be confined to the higher peaks of the mountains. Temperatures
will be mild, in the mid to upper 50s for much of the lowlands.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A frontal system is on track to dig into western Washington
Saturday night into Sunday, bringing in ample lowland rain and
mountain snow alongside breezy southerly winds. The front will
push east of the Cascades by Sunday afternoon, clearing up
rainfall over the lowlands with lingering showers over the
mountains. The lowlands will see roughly half an inch to an inch
of rain with this system, with liquid amounts up to 2 to 3
inches over higher terrain. Snow levels will drop to 3500-4500
feet behind the front, with significant snow accumulations
possible generally above 4000 feet. Despite some uncertainty
over snowfall amounts, the Cascade Passes will likely see at
least a few inches of snow accumulation through Sunday night.

A weak shortwave trough will follow closely behind on Monday,
maintaining widespread showers that will add up to an inch or
two to snow totals over the mountains. Temperatures will cool
off several degrees, with most lowland locations barely reaching
50 degrees.

Forecast confidence decreases into the middle of next week, with
ensembles showing potential for an upper level ridge to build
over the Pacific Northwest. However, operational forecast models
show continued chances for lowland rain and mountain snow into
Wednesday and Thursday. Snow levels may drop as low as 1500-2000
feet by the middle of next week, but a large degree of
uncertainty remains in the forecast. Conditions that may impact
holiday travel will continue to be closely monitored.

15

&&

.AVIATION...
A trough will swing a split-frontal system through the
region early this morning. Radar is showing showers moving through
the interior terminals in a north direction (as of 09Z). Most of
these showers will wrap up by around 15Z (few isolated showers will
linger through the afternoon). Visibilities may briefly drop down to
4 to 6 mi with some brief mist mixed in. Ceilings have dropped to
MVFR behind the line of showers (closer to the actual frontal
boundary), so will continue the brief mention of MVFR ceilings post-
showers for remaining interior terminals this morning (as model
guidance keeps a high likelihood of MVFR cigs post-rain through late
morning). Scattered to broken ceilings at lower-end VFR are favored
through the remainder of the day, with light S-SW winds 4-8 kt. The
flow aloft will remain W-SW.

KSEA...Radar showing showers moving through the terminal as of 09Z
this morning - expected to clear out by 15Z at the latest. Brief
MVFR remains likely between 12Z and 18Z (once the shower activity
has wrapped up), with ceilings improving to VFR shortly after
(remaining scattered to broken and between 3,000-5,000 ft). Winds
SSW 4-8 kt.

HPR

&&

.MARINE...
A split-frontal system over the coastal waters this
morning will move inland with an associated trough. Flow will relax
out of the south this morning with light winds expected across the
waters. The main concern for Thursday remains 15-18 ft. seas at 15
seconds (with a west swell) over the coastal waters, west Strait of
Juan de Fuca, and the Grays Harbor bar - thus the small craft
advisory will continue in these areas through Friday. A stronger
frontal system will impact the waters this weekend, with seas
remaining above 10 ft (10-14 ft.) through the weekend, and a medium
chance of wind gusts above 20 kt in the coastal waters (also a
medium chance for gale gusts in the Strait of Juan de Fuca Sunday
into Monday). The seas are expected to remain above 10 ft through
Monday evening, before dropping back down to 6-8 ft., and further
down to 5-6 ft. midweek.

HPR

&&

.HYDROLOGY...
At this time, no flooding is forecast over the next 7 days.
Stronger weather systems moving into the region early next week
could bring periods of heavier rain and mountain snow, and will
be the next time frame to watch with respect to hydrologic
concerns.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from noon today to noon PST Friday for
     Grays Harbor Bar.

     Small Craft Advisory until 4 AM PST Friday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From James Island To Point Grenville
     Out 10 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater Out 10 Nm-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 10 AM PST this morning for East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$