Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
499
FXUS66 KSEW 282335
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
335 PM PST Sun Dec 28 2025
.SYNOPSIS...
An upper level ridge will continue to build over Western Washington
and persist through midweek, bringing drier conditions and patchy
fog to the region. An active weather pattern may return as early as
Thursday, bringing back lowland rain and mountain snow into the
weekend.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
Latest satellite imagery shows mid to high level clouds moving
over Western Washington this afternoon. As a result, the fog in
the Chehalis Valley has struggled to scatter out this afternoon.
An upper level ridge will be the prominent weather feature
through at least midweek. This ridge will keep conditions dry
across Western Washington. While conditions will remain dry,
abundant lingering moisture may lead to patchy fog formation
overnight, especially along the southern interior and Chehalis
Valley. High temperatures will generally be in the mid to upper
40s. Low temperatures will be on the chilly side, with values in
the low to mid 30s and upper 20s along the Chehalis Valley.
With an upper level ridge in place, stable conditions may
develop and lead to an inversion on Tuesday and Wednesday. This
may lead to stagnant conditions to develop. 29
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Long-range ensembles have the upper level ridge persisting over
the region through at at least Wednesday, keeping conditions
dry. Model solutions start to defer slightly on Thursday on the
arrival of the next system. Depending on what scenario plays
out, it will determine the next arrival of precipitation for the
region. An active weather pattern is favored to continue into
the weekend.
The threat of minor coastal flooding increases late in the week.
While there is uncertainty in the timing and strength of the system,
at this time it does not appear to exacerbate coastal flooding.
29
&&
.AVIATION...
Northwesterly flow will persist aloft through the TAF period
as a upper ridge level ridge builds into the region. A thermal
trough at the surface will build along the coast on Monday,
allowing for low level flow to transition to more east-
northeasterly.
Mid to high clouds continue to stream in over the area as a
frontal system moves into British Columbia this afternoon. As a
result, low clouds and fog have not scattered out much for
areas south of Puget Sound this afternoon. Conditions at terminals
like KOLM in fog remain LIFR, while conditions elsewhere remain
VFR this afternoon. Expect fog to redevelop and expand for areas
south of the Sound into Monday morning. With cold overnight
temperatures, terminals like KOLM will likely see another round
of freezing fog overnight.
Winds remain light and variable for the majority of the area
terminals this afternoon, however will transition to more
northeasterly by tonight. The combination of mid to high level
cloud cover and northeasterly winds may help mitigate fog
development for terminals east of Puget Sound on Monday morning.
KSEA...VFR conditions with light northerly winds between 3-6
kt, transitioning to the northeast tonight. While a few low
clouds will be possible within the vicinity of the terminal on
Monday morning, northeasterly winds may help limit fog potential
and keep VFR conditions prevalent at the terminal through the
period.
14
&&
.MARINE...
High pressure will remain situated over the coastal waters
through Wednesday. Meanwhile, a weak thermal trough will build
along the coast on Monday. This will continue to promote offshore
flow through the first half of the week. Seas ranging between 3-6
ft today will build to 6-9 ft late tonight into Monday as systems
pass by to the north and a west-northwest swell moves into the
coastal waters.
Dense fog may develop over portions of the interior waters with
clearing conditions and light winds during the overnight periods
the over the next few days and will likely restrict visibilities
across the waters at times.
A more active pattern returns the second half of the week, with
the next frontal system expected to move into the area waters
on Thursday. This will allow for flow to transition back to
southerly. Increasing winds and seas will likely bring the next
round of headlines to the area waters.
14
&&
.HYDROLOGY...
No river flooding is expected during the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion