425
FXUS66 KSEW 280417
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
817 PM PST Thu Nov 27 2025
.SYNOPSIS...
An area of low pressure moving onshore tonight will keep rain
in the forecast before drier conditions develop on Friday as the
system shifts eastward. Cooler and generally drier conditions are
expected over the weekend into early next week with a couple of weak
systems clipping the region.
&&
.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
An area of low pressure moving onshore over the south Washington
coast will keep things rather wet across the southern half of the
CWA overnight, then drier conditions will develop tomorrow as weak
high pressure builds into the area. A couple of weak systems will
clip the area in northwest flow aloft late Saturday and again
Monday, but they look rather inconsequential at this time. Current
forecasts are on track. Previous discussion follows with update to
aviation portion. 27
After a bit of a lull this morning between the rounds of
precipitation, it`s going to be a damp end to the Thanksgiving
Day holiday as the next round of rain is filling in across
Western Washington. The associated cold front is pushing into
the coastline early this afternoon with the trailing low
pressure still offshore entering the coastal waters. Snow levels
are starting off at around 4500 ft or so across the region and
will remain somewhat high while the moisture streams across the
region. Expect showers to taper from northwest to southeast
overnight and through the morning Friday as the low advances
onshore somewhere south of Grays Harbor or near the mouth of the
Columbia River. Ahead of this low, expect to see some gusty
winds this evening, with some gusts into the 30-35 mph range
across the coastline and into the interior through the Chehalis
valley. Winds will ease as the low continues to push southeast
inland and continue to weaken.
High pressure then builds over the northeastern Pacific through
the day Friday, with the air mass beginning to dry out. Ensemble
guidance does vary a bit with the strength, and likely keep it
positioned such that a passing impulse Saturday will bring some
additional clouds and perhaps even some light rain. We`ll also
see a gradually cooling trend with overnight lows dipping a few
degrees cooler each of Friday and Saturday night. Saturday night
may bring widespread temperatures into the lower 30s around the
lowlands of Western Washington. 12
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
High pressure again in place on Sunday with the shortwave
quickly passing through the flow. This will maintain cooler but
dry conditions across the region, with another chilly start
Monday morning. Decent agreement in the ensemble guidance
suggesting another weak disturbance may be able to push through
late Monday night into Tuesday, perhaps again bringing some
light mountain snow and lowland rain. Accumulations of both are
rather low and not particularly unusual or impactful for this
time of year. Even with this passing disturbance, the ridge is
likely to rebound for another few days of drier conditions in
place across the region. 12
&&
.AVIATION...
West to southwest flow aloft will shift to northwesterly
overnight as a vertically stacked trough moves onshore across
southwest Washington. Area of MVFR ceilings in diminishing
rain are expected from around KPAE southward overnight. Areas of IFR
stratus are likely to form across south Puget Sound and the
Southwest Interior by morning. Ceilings will lift and scatter by
midday with VFR expected most terminals on Friday afternoon.
KSEA...Periods of MVFR are expected later tonight into Friday
morning with rain diminishing overnight. Ceilings will lift and
scatter out 18Z-20Z. Surface winds E/NE 6 to 10 knots shifting N/NE
4 to 7 knots by mid-morning Friday. 27
&&
.MARINE...
.A strong low pressure system continues to move through the
coastal waters this afternoon with a cold front pushing onshore.
The low will track onshore this evening between Grays Harbor
and the mouth of the Columbia River tonight before shifting
inland and weakening. With this path, expect backing winds from
S/SE to N into the evening hours. While widespread gales are
not expected, occasional gusts to 35 kt will likely develop
ahead of and south of the low track. Seas will also build to
around 11 to 15 ft and remain rather steep with dominant periods
initially around 8 to 9 seconds.Winds will also remain enhanced
through the western and central portions of Strait of Juan de
Fuca. Winds ease by early Friday, with seas subsiding through
the day. High pressure then rebuilds this weekend and into the
start of next week, and offshore flow will develop over the
waters. 12
&&
.HYDROLOGY...
A passing frontal system and associated low will bring one last
push of heavier rain across the region this evening into early
Friday. Snow levels will remain above 4000 feet, leaving the
majority of the precipitation falling as rain. With expected
rainfall amounts holding steady and topping out mostly in the 2
to 2.5 inch range with this system, confidence is increasing
that we will not see any river flooding impacts. After tonight,
there is no additional hydrologically significant precipitation
expected through the next seven days. 12
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 4 AM PST Friday for Central U.S.
Waters Strait Of Juan De Fuca-Coastal Waters From Cape
Flattery To James Island 10 To 60 Nm-Coastal Waters From
Cape Flattery To James Island Out 10 Nm-Coastal Waters
From James Island To Point Grenville 10 To 60 Nm-Coastal
Waters From James Island To Point Grenville Out 10 Nm-
Coastal Waters From Point Grenville To Cape Shoalwater 10
To 60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm-Grays Harbor Bar-West Entrance U.S.
Waters Strait Of Juan De Fuca.
&&
$$
NWS SEW Office Area Forecast Discussion
