887
FXUS66 KSEW 181148
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
348 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/...
Widespread showers evident on radar this morning with an upper
level disturbance spreading across the area. Snow levels have
lowered to around 3000 ft, so could see a light accumulation of
up to an inch or so over Snoqualmie and Stevens passes early
this morning and slightly higher amounts in the North Cascades
around Rainy Pass. As another impulse tracks through the region,
expect to see some showers continue through the day. 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. 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...
Westerly flow aloft, turning more west-northwesterly as the TAF
period progresses. A mix of VFR to MVFR so far this morning with
isolated LIFR. This trend will likely persist throughout the rest of
the morning until improvement is met with more widespread VFR into
the the afternoon. With abundant low-level moisture and ridging
building, widespread fog will be a concern overnight tonight into
Wednesday morning with LIFR conditions expected but should scour out
by the afternoon as a front draws offshore with rainfall arriving by
the evening.

KSEA...MVFR remaining stubborn this morning until improvement to VFR
is met this afternoon. Uncertainty exists in exact timing of
improvement is expected but after 18-20z appears to be the best
window. VFR will remain 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.

McMillian

&&

.MARINE...
Seas continue to very gradually ease over the coastal waters
this morning, and the small craft advisory for the outer coastal
waters was allowed to expire early this morning. This will bring
a break in the marine hazards for the next day or so 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

&&

.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.

&&

$$