Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
209
FXUS66 KSEW 310949
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
249 AM PDT Mon Aug 31 2026
.SYNOPSIS...Weak upper ridging over the Pacific Northwest will
bring dry weather to begin the week. A stronger early season
system Wednesday into Thursday results in more widespread
rainfall and gusty winds. The deep upper low lingers over the
Pacific Northwest into next weekend for cooler conditions.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Mainly clear skies
early this morning across Western Washington with weak upper
ridging in place. Localized fog and low stratus may develop
early this morning, otherwise, high clouds will be around at
times today. Dry conditions continue through tonight. Highs
today peak in the 70s for most areas.
Troughing begins to approach the Pacific Northwest offshore on
Tuesday with increasing clouds. Although Tuesday is expected to
be predominantly dry into the afternoon for most locations, a
few showers begin to increase in the afternoon, with a 10%
probability of thunderstorms in the Cascades late due to
increasing south flow aloft.
A very deep, anomalous early season upper low moves southwards
out of the NE Pacific into the offshore waters on Wednesday.
This system will bring widespread rain into Western Washington
Wednesday through Thursday. The heaviest rainfall is expected
over the Olympic Peninsula given the vicinity of the upper low,
however, measurable rainfall is expected for all locations. In
addition to the rain, gusty winds are expected, especially for
early September standards, as noted on the ECMWF EFI. NBM
highlights the probability for wind gusts exceeding 40 MPH
between 30 to 70% for the immediate coast, Whidbey Island, San
Juan Islands, and western Whatcom County. Elsewhere, gusts of 25
to 35 MPH are forecast at this time. Given the vegetation on
trees, early season wind impacts such as blown down tree limbs
and isolated power outages can`t be ruled out. Temperatures drop
into the 60s on Wednesday due to the presence of the stronger
system by midweek.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...Unsettled
conditions continue into Thursday as the upper low placement
remains offshore of Washington and Oregon. Showers will remain a
threat Thursday. Thunderstorm probabilities also increase
towards 15 to 30% on Thursday, and will need to monitor the
lightning threat in heavier showers. Although winds will be
lighter on Thursday, continued south winds remain locally
breezy. Ensembles are in good agreement of troughing over Oregon
and Washington Friday into Saturday. The rain threat is expected
to slowly diminish during this period, but wrap around moisture
may still bring continued precipitation to some areas.
Uncertainty begins to increase by late weekend, however,
ensembles do begin to show troughing slowly moving eastwards
heading into next week. JD
&&
.AVIATION...A brief upper level ridge will build over the
terminals today with high pressure underneath. A trough will dig
southward offshore on Tuesday, which will result in the flow
aloft switching from west/northwest to southwest. Satellite
still reflects mid and high cloud coverage across most
terminals. ACARS soundings this morning shows a large dew point
depression over the Puget Sound terminals this morning (around 8
degrees this morning). As a result, the fog formation this
morning is going to be limited to areas that are able to cool
off the most, as well as with light or calm winds, and near
moisture sources. Highest probabilities for IFR/LIFR conditions
remain the Pacific/Strait of Juan de Fuca coastlines at 30-40%
chance this morning. This trickles down to 10-20% for south
interior, as well as north Puget Sound and South Interior
locations (which will be more isolated compared to the coast).
Any fog that does form will clear around 18Z for VFR skies the
remainder of Monday. Winds today will remain out of the north at
5 kt or less this morning, becoming 5-10 kt during the day.
They will become light and variable tonight and switch to the
south Tuesday.
KSEA...VFR conditions anticipated to continue through the TAF
period. Fog likelihood is around 10% this morning, but the formation
is likely to remain isolated around the terminal (if indeed it does
form). Winds increase to 5-10 kt during the day, but become variable
under 5 kt tonight as they switch to the south. There is a 20-40%
chance of MVFR ceilings Tuesday morning.
HPR
&&
.MARINE...High pressure will remain offshore over the coastal
waters and into Tuesday. Benign conditions with light winds will
continue into Tuesday as a weak system bypasses to the north. A
significant pattern change remains on track midweek with a
large-scale low pressure system and front dropping down from the
Gulf of Alaska Wednesday into Thursday. Confidence has remained
persistent with the 60-80% likelihood for most of the coastal
waters, the east Strait of Juan de Fuca and Admiralty Inlet
waters over the past 3 days with the model data. A gale watch
was issued for these areas for the day Wednesday as sustained
winds of 25-35 kt remain likely, and some potential for a couple
gusts to 40 kt. Remaining waters will likely see some impact
from gusty winds out of the south and southeast with this
system, though the threat of gale gusts is much less (for Puget
Sound/Admiralty, and the central/west Strait of Juan de Fuca
sections). The system will also bring several rounds of rain and
a slight chance of thunderstorms for the coastal waters on
Wednesday. The system will move out again on Thursday, and winds
will decrease significantly going into the weekend.
Seas will remain at 3-6 ft through late Tuesday. The midweek system
will bring seas around 8-11 ft Wednesday into Thursday, but will
drop back to 4-6 ft Friday into next weekend.
HPR
&&
.FIRE WEATHER...A brief warming and drying trend will occur
today under weak high pressure. Relative humidity minimums in
the central and southern Washington Cascades will decrease to
around 25 to 30 percent this afternoon. Finer, flashier fuels
will be more apt to respond to the dip in RH. More clouds arrive
ahead of the stronger system for only partly sunny skies on
Tuesday. By late Tuesday night into Wednesday, the stronger
system arrives for widespread rain, windy conditions, and slight
chances for thunderstorms.
21
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Watch from Tuesday evening through Wednesday evening for
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-East
Entrance U.S. Waters Strait Of Juan De Fuca-Northern
Inland Waters Including The San Juan Islands.
&&
$$
NWS SEW Office Area Forecast Discussion