034
FXUS66 KSEW 012141
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
141 PM PST Mon Dec 1 2025

.SYNOPSIS...
Generally quiet weather is expected through Wednesday night or
Thursday. The door will open to a series of weather systems
beginning Thursday and continuing into next week. Initially the
concerns will be gusty winds and the potential for coastal
flooding, then transition to a river flood threat with a
continued coastal flood threat as we move through the weekend
into next week. Active weather is likely to continue through at
least the first half of next week.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Generally quiet conditions are expected in the short term. A
weak frontal will push through tonight into early Tuesday
bringing with in some light precipitation with little impact
expected. A ridge will nose into the region Wednesday, keeping
the area relatively dry. Patchy fog will be possible each
morning.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
By Thursday, weak waves moving over the top of the ridge could
begin to increase precipitation chance Thursday, but the ridge
breakdown is more likely to occur Friday. Beginning Friday, the
door will open to periods of moderate to heavy precipitation
associated with moisture plumes originating from the subtropics.
While each of these periods alone appear unlikely to cause
issue, the successive nature could result in a increased risk of
flooding as early as this weekend, but perhaps more likely by
early next week. In addition, rainfall-driven landslide
indices are also approaching seasonal thresholds and by early
next week the landslide risk could become the highest yet seen
this season.

In addition, hazards associated with coastal flooding and wind
will become elevated late this week, likely peaking late this
weekend or early next week. Currently, the coastal flood risk
appears to peak along the outer coast Thursday through Saturday
this week, but at this time, only appears to flirt with minor
flood thresholds. The concern is higher for the inner coast of
the Puget Sound and Salish Sea from Friday into early next week.
Current models indicate multiple days of water levels well above
minor flood stage, and a few locations (particularly Cherry
Point and Friday Harbor) flirting with moderate or higher flood
levels. The actual level of impact will strongly depend on the
overlap of low pressure and elevated winds which are a challenge
to nail down at this lead time.

Looking out beyond the next 7 days, the Climate Prediction
Center has included a moderate (40-60%) chance of hazardous
rain, high elevation snow, and winds continuing through December
10.
-Wolcott-

&&

.AVIATION...
West to northwest flow aloft will continue with an upper level ridge
centered well offshore. A weak frontal system will reach the area
tonight with deteriorating ceilings and areas of light
precipitation. VFR ceilings will lower to MVFR overnight. A mix of
MVFR and IFR will prevail areawide on Tuesday with light surface
flow and a moist air mass in place.

KSEA...VFR ceilings will lower to MVFR tonight as a weak system
spreads some light rain across the area. Precipitation will
dissipate on Tuesday, but low MVFR or occasional IFR ceilings will
persist throughout the day tomorrow. Light and variable surface
winds will become southerly 7 knots or less tonight, then return to
light and variable or very weak northerly during the day on Tuesday.

27

&&

.MARINE...
A weak frontal system will cross the Pacific Northwest tonight
into Tuesday resulting in small craft winds beyond 10 nm
offshore. Seas will also increase from 4-6 ft Monday to 9-12 ft
Tuesday through Wednesday. Benign conditions are expected
behind this system, with light winds, and seas returning to 4-6
ft. A stronger system Friday through the weekend may bring small
craft advisory level winds to the coastal waters, and a few of
the north interior waters. There is also a medium chance at this
time for gale winds in the Strait of Juan de Fuca. Seas will
also increase to 9-13 ft with this system Friday through the
weekend into early next week.

Wolcott/HPR

&&

.HYDROLOGY...
A series of at least two (and potentially more) atmospheric
river events with subtropical origins is currently expected to
impact the area beginning roughly Friday and continuing through
the weekend into early next week. Given the lead time, there is
still quite a range of potential outcomes, but there is at
least a chance of a significant flood event beginning as early
as this weekend, but more likely early next week. Based on the
latest HEFS guidance, the median (50th percentile) forecast
would result in only a few rivers reaching action stage, while
the higher end scenarios indicate the potential for significant
flooding. The 90th percentile (reasonable high end) in
particular indicates the potential for a few rivers to reach
major flood stage. These higher end scenarios would also bring
with it an elevated rainfall-driven landslide risk.
-Wolcott-

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from midnight tonight to noon PST Tuesday
     for Coastal Waters From Cape Flattery To James Island 10
     To 60 Nm-Coastal Waters From James Island To Point
     Grenville 10 To 60 Nm-Coastal Waters From Point Grenville
     To Cape Shoalwater 10 To 60 Nm.

&&

$$