Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
796
FXUS66 KSEW 302236
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
236 PM PST Tue Dec 30 2025
.SYNOPSIS...
Dry weather will continue with high pressure in place through
Wednesday. Some areas that remain clear next couple mornings
will continue to have the potential to see areas of fog. The new
year will bring a return to active weather for western
Washington, with a series of systems passing through into early
next week producing light to moderate amounts of precipitation.
High tides will also increase the risk of coastal flooding by
Friday.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY/...
Upper level analysis shows a negatively tilted ridge from the
four corners region of the U.S. up into the Pacific Northwest.
Satellite has cleared up some from this morning with a mix of
high clouds and sun continuing through the rest of today. There
remains a corridor of patchy fog in the Chehalis-Olympia-
Lakewood corridor as of late this morning. Model guidance
still have the fog in this corridor lingering through early this
afternoon (though there is still a strong likelihood of mist
hanging around through the evening). Highs this afternoon will
reach the mid to upper 40s (few 50s on the Cascades slopes and
along the coast), and winds becoming light out of the south
through tonight/tomorrow. Lows tonight will likely drop to
around freezing, with a few sub 30s in the south interior (cloud
coverage is expected to be similar to this morning with a mix of
high clouds).
The upper level ridge pattern will hold into Wednesday. Another
round of fog appears likely in the morning. Main caveats are:
how much of the cloud coverage tonight will hinder development,
and how strong the temperature inversion will be for holding
surface moisture in. The forecast soundings show a significant
inversion with warmer air aloft Wednesday morning. The highest
probabilities for seeing visibilities less than 1/2 a mile are
the south Puget Sound/Kitsap and Chehalis Valley areas. This
lessens to a 10-15% for the rest of the forecast area. The risk
of air stagnation remains low, although a few areas may see
locally degraded air quality with the strong inversion
overhead. The remainder of Wednesday is dry to wrap up 2025 with
fewer clouds going into the afternoon. Temperatures will be
similar to Tuesday.
By new years day (Thursday), the ridge will begin to broaden and
weaken as an embedded shortwave impulse traverses the WA/OR
coastline Thursday into Friday. A weak surface system with this
impulse will move through Thursday into Friday. The southern
4/5ths of the forecast area (excluding the NW interior coast)
will have a 30-50% chance of showers through the day, with
chances increasing regionwide through the evening. QPF Thursday
is expected to remain light (few hundredths), with snow levels
remaining around 4,000-5,000 ft. Winds Thursday will remain
light. High temperatures remain steady (from Tuesday/Wednesday)
with overnight temperatures Thursday night warming into the
upper 30s/low 40s.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The weak impulse Friday will be replaced by a more broader
shortwave trough moving up the WA/OR coast, passing through the
region into the weekend. This will increase precipitation
chances up to a 70-90% chance regionwide the later part of
Friday into Saturday, decreasing into Sunday. Snow levels with
this shortwave will drop from 5,000-6,000 ft down to around
3,000 ft through the weekend. The total amount of liquid water
(QPF) coming from this system through the weekend remains light
overall, with most likely the lowlands seeing around half an
inch of rain, and the Cascades/coast seeing anywhere from around
an inch to two inches. The Olympics have a slight chance of
seeing heavier amounts of QPF upwards of 2-4". Much of the QPF
in the mountains will turn to snow late Saturday into Sunday as
the snow levels drop. The recent forecast package saw a downward
trend in snow accumulations in Snoqualmie/Stevens passes (due
to the delay in the snow level drops). The bulk of the snow
accumulations remains the north Cascades and Olympics, with the
best chance of advisory amounts of snow (greater than 6").
Breezy winds appear likely with the system Saturday night into
Sunday, with most likely wind gusts in the 25-35 mph range
(there is a 10% chance of gusts over 45 mph for the interior,
and a 10% chance of gusts over 55 mph along the coast).
The ensembles keep the progressive pattern going into the next
week with all members showing a cool/wet pattern returning into
the region. Its worth mentioning that the moist conveyor belt
remains to the south in California next week (responsible for
producing a lot of the atmospheric river conditions this month
across the west coast). Temperatures in this period will hover
in the upper 40s for highs, and upper 30s for lows.
Additionally, astronomically large tides will increase the risk
of minor coastal flooding, beginning Friday and lasting through
the weekend. As confidence increases regarding the
strength/track of the system as well as waves/winds, additional
details regarding impacts will be shared.
HPR
&&
.AVIATION...
An upper level ridge pattern will remain over the terminals rest
of today into Wednesday. Flow aloft will weaken out of the
southwest. Satellite this afternoon shows a pocket of fog slowly
eroding in the Chehalis Valley (terminals continue to report
LIFR conditions with 2 SM mist and low stratus). A pocket of low
stratus clouds continues to produce locally MVFR conditions
along the Strait of Juan de Fuca. Remaining terminals outside of
this area are reporting VFR conditions, with high clouds and
light NE winds 3-6 kt. Winds will decrease tonight to under 5
kt out of the south, becoming calm in some spots. Cloud coverage
will remain about 50/50 through tonight/Wednesday. Warm air
advection aloft will make the atmosphere stable going into
tonight/Wednesday. This concerns the potential for fog Wednesday
morning (especially with a strong inversion despite the partial
cloud coverage). The highest chance of seeing fog remains the
south interior (up through south Puget Sound/Kitsap) through
most of tonight with most models showing a surge of fog moving
up into the Seattle area between 14-18Z. Another area of fog is
likely to develop in the Everett-Mt. Vernon corridor
tonight/tomorrow morning. Clearing will take place late
Wednesday morning/afternoon, with VFR conditions/high clouds
rest of Wednesday. Winds will remain light out of the south
Wednesday.
KSEA...VFR through tonight. Fog to the south will develop
overnight, and push towards the terminal around sunrise
Wednesday morning. The highest chance for fog in the terminal is
from 14-18Z, with a 30-40% chance of visibilities less than 0.5
SM during this window. Once the fog clears, VFR conditions are
expected for the remainder of Wednesday. NE winds 4-6 kt will
shift to the south later this evening, becoming less than 5 kt
tonight/Wednesday.
HPR
&&
.MARINE...
A ridge/high pressure pattern over the waters will keep
conditions quiet/calm through the end of the week. A thermal
trough also remains in place through the first half of the week,
keeping the flow offshore. The pattern remains favorable for the
development of areas of patchy to locally dense fog over
portions of the interior waters Wednesday and Thursday mornings.
The seas through Friday will hold around 6-8 ft. A weak
disturbance will pass over the waters Thursday/Friday, with a
stronger system passing through late Friday through Sunday. A
period of breezy south winds of 20-25 kt appears likely
Saturday/Sunday over the coastal waters and Strait of Juan de
Fuca. Seas will also increase to 14-16 ft Saturday with this
system, then decrease to 6-8 ft Sunday through early next week.
HPR
&&
.HYDROLOGY...
Precipitation will return Thursday through early next week,
which may cause small rises in rivers, creeks and streams. No
rivers are currently forecasted to flood at this time, however
the Skokomish River is expected to rise above action stage with
the precipitation falling this weekend.
HPR
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion