078
FXUS66 KSEW 172311
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
311 PM PST Mon Nov 17 2025

.SYNOPSIS...
Showers will continue across the area into Tuesday as a series
of disturbances makes its way across the region. Drier conditions
are expected late Tuesday into Wednesday as a ridge of high pressure
briefly moves over western Washington. Rain chances increase again
late Wednesday into Thursday as another system approaches and
splits across the area. Additional weak systems may brush the
region over the weekend, with more significant precipitation
expected to impact the area by early next week.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Latest radar shows showers continuing to lift northward across
the area this afternoon in association with a stalled frontal
system draped across the region. Expect showery conditions to
continue across western Washington into Tuesday as an upper
level disturbance makes its way across the area this evening.
This disturbance could bring a period of heavier precipitation
for the northern tier of the area tonight. While not expecting
much in the way of impacts, a period of mountain snow is expected
for the Cascades into Tuesday as snow levels dip from 6500 ft
to 3000-3500 ft by early Tuesday. This may bring a few inches
of snow to areas like Rainy Pass in the North Cascades and could
even bring around an inch to lower passes like Stevens and
Snoqualmie by Tuesday morning.

Another upper level disturbance will move across the area on
Tuesday, but generally expect showers to taper across western
Washington throughout the day as the moisture decreases. The
system will exit the region by Tuesday night, allowing for upper
level ridging to build back into the region in its wake. Drier
conditions are expected Tuesday night and Wednesday as a result.
Clearing skies Tuesday night will increase the potential for
fog development overnight into Wednesday with light winds and
ample moisture remaining in the low levels. Wednesday will
remain dry across the region, but expect an increase in high
cloud cover throughout the day as the next system approaches.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Precipitation chances start to increase again by Thursday as a
weak, splitting system approaches the area. Overall rainfall
amounts look to remain rather light at this time, with showers
mainly expected to move in along the coast and Olympic Peninsula
and largely remain west of Puget Sound. Additional, wetter
systems may move into the area over the weekend for another
round of lowland rain and mountain snow.

Ensemble guidance then remains rather split in solutions
heading into early next week, with latest cluster analyses
showing roughly 45 percent of the ensemble members highlighting
a cooler period for western Washington with shortwave troughing
situated over the region, while roughly 35 percent of the
members highlight a warmer period with some amplitude of
ridging over the Pacific Northwest. Should the colder solution
take hold, could see more significant snow for the mountains and
the mountain passes by early next week.

14

&&

.AVIATION...
A frontal boundary will move east of the Cascades
this afternoon with southwest flow aloft transitioning to west
to northwesterly as a weak upper trough moves onshore. Light
surface flow and plentiful low level moisture will contribute to
the development of widespread IFR or low MVFR stratus tonight
into Tuesday morning.

KSEA...
Limited improvement is expected this afternoon with ceilings
briefly lifting to MVFR at best. Ceilings are expected to
deteriorate once again tonight with low end MVFR or occasional IFR
expected for Tuesday morning. Light and variable surface winds late
this afternoon will switch to southerly 4 to 7 knots overnight
through Tuesday midday then veer northerly by Tuesday evening. 27

&&

.MARINE...
A broad surface ridge will rebuild over the coastal and
offshore waters through Tuesday. The ridge will then shift east of
the Cascades on Wednesday as a splitting front approaches the outer
coastal waters. This will turn the flow east to southeasterly
midweek. Broad surface ridging rebuilds late in the week before
another weak front approaches the waters over the weekend.

Coastal seas will dip below 10 feet on Tuesday and Wednesday before
another larger swell train arrives Thursday into the weekend.  27

&&

.HYDROLOGY...
No flooding is expected through the week ahead. Stronger weather
systems moving into the region next weekend and into early next
week could bring periods of heavier rain and will be the next
time to watch with respect to hydrologic concerns.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 4 PM PST this afternoon for Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville Out
     10 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm-Grays Harbor Bar.

     Small Craft Advisory until 10 PM PST this evening 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.

&&

$$