469
FXUS66 KSEW 180335
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
735 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/...
The latest forecast remains on track with no updates this
evening. Latest radar shows showers continuing to lift
northward across the area this evening 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...
Mostly MVFR to IFR this evening as showers continue to shift
northeastward along an exiting frontal system. Southwest flow
aloft will continue to transition 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, with some pockets of LIFR low stratus. Conditions are
favored to remain deteriorated into the afternoon Tuesday, with
potential for some terminals to briefly break out to low-end VFR
ceilings Tuesday evening before returning to MVFR/IFR in
continued low clouds and isolated showers.

KSEA...Limited improvement this evening as ceilings bounce
between low-end VFR and MVFR. Ceilings are expected to
deteriorate once again tonight with high potential for MVFR/IFR
conditions overnight into Tuesday morning. Forecast models
maintain a 50% chance of ceilings below 2000 ft for much of the
TAF period into the early afternoon Tuesday. Ceilings are
favored to briefly lift to low- end VFR Tuesday evening before
falling to MVFR/IFR once again Tuesday night. Confidence is
much lower for visibilities, with a low chance (10% to 15%) of
fog developing Tuesday morning at the terminal bringing vis
below 6 miles. Southerly winds generally 4 to 7 kt will veer
northerly by Tuesday evening.

15

&&

.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 frame to watch with respect to hydrologic concerns.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...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.

&&

$$