417
FXUS66 KSEW 181656
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
856 AM PST Tue Nov 18 2025

.SYNOPSIS...
Showers will continue across the area today as a disturbance
crosses the region. Showers gradually diminish tonight with
mostly dry conditions by Wednesday as high pressure builds over
western Washington. Rain chances increase again late Wednesday
into Thursday as another system approaches and splits across the
area. Additional disturbances reach the area this weekend into
the start of next week, with more significant rain and mountain
snow expected to reach the area.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
Radar imagery this morning continues to show very light isolated
showers across the area this morning. With snow levels around
3500 ft, some light accumulation may be possible at Stevens Pass
and higher, with a light mix possible at Snoqualmie Pass.
Showers will continue through the day as another impulse tracks
through the region, however, a ridge of high pressure will
begin to build across the area later today, limiting the
moisture available and bringing an end to the precipitation for
now. 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. Another weak system begins to approach, but
is again expected to split as it moves into Western Washington.
This will bring some rain and mountain snow, but more
significantly for most just another round of cloudy conditions.
There is an increasing signal for increasing easterly gap winds
on Wednesday with the potential for peak gusts reaching 35-40
mph near the entrances near North Bend, Gold Bar, etc. with
elevated winds reaching further west towards the Eastside metro.
Will continue to evaluate for the afternoon update. Thursday
also looks to be drier for the southeastern portions of the
region with another system moving through the northwestern part
of the state into southern B.C.

62/Cullen

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Confidence continues to increase with respect to the potential
for additional active weather this weekend into next week,
though ensemble guidance does continue to depict a fairly large
spread of potential outcomes. Should the colder solution
take hold, represented by roughly 40-50% of ensemble members,
there would be the potential for more significant snow for the
mountains and the mountain passes by early next week.  Cullen

&&

.AVIATION...
Flow aloft will become more northwesterly throughout the day
today as an upper level disturbance exits the region and an upper
level ridge starts to move in. Conditions remain a mixed bag of
mostly VFR to MVFR this morning, though there are some isolated
spots of IFR/LIFR in low clouds and fog. This trend will likely
persist throughout the the morning hours until improvement
towards more widespread VFR conditions returns by this afternoon.
With abundant low-level moisture, ridging building overhead,
and clearing skies, can expect widespread fog to be a concern
overnight tonight into Wednesday morning. IFR to LIFR conditions
will be expected in fog, with fog expected to scour out by the
afternoon as a front approaches from the Pacific and rainfall
arrives by the evening. Easterly gap winds will also increase
during morning hours on Wednesday, becoming breezy during the
afternoon and evening. East winds may make it into the central
Puget Sound terminals, with gusts to 15-25 kt at times.

KSEA...MVFR conditions this morning, with improvement to VFR
expected by this afternoon. Uncertainty exists in exact timing
of improvement is expected but after 18-20z appears to be the
best window. VFR conditions will persist into the evening with
mostly clear skies, but fog looks to form overnight into early
Wednesday morning. Southerly winds this morning 4-8 kt, turning
more northerly after 00z. Winds will then shift more to the east
between 15-18Z Wednesday and may become breezy to 15 to 25 kt
at times.

McMillian/14

&&

.MARINE...
Seas have now eased to around 5 to 8 ft across the coastal
waters this morning. Tranquil conditions will continue today,
bringing a break in the marine hazards for today with weak
winds as broad high pressure builds over the waters today and
remains through the first part of Wednesday. The ridge will then
shift east of the Cascades on Wednesday as a splitting front
approaches the outer coastal waters. Advisory strength gusts are
expected across portions of the waters late Wednesday into
Thursday. Broad high pressure rebuilds late in the week before
another front approaches the waters over the weekend with
another more active pattern taking shape into early next week.

Expect to see seas build over the coastal waters late Wednesday
and especially Thursday, with the arrival of a longer period
wave group into the waters. This will bring seas into the 15-17
ft range Thursday and generally holding above 10 ft over the
coastal waters through the start of next week.     Cullen/62

&&

.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...None.

&&

$$