Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
881
FXUS66 KSEW 050926
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
226 AM PDT Wed Aug 5 2026
.SYNOPSIS...
Upper level ridge over Western Washington through Thursday. The
ridge will slowly drift east Friday. Zonal flow Saturday into
the first part of next week. In the lower levels thermally
induced trough over the area through Thursday will move east
Thursday night. Varying degrees of onshore flow Friday through
next Tuesday.
&&
.SHORT TERM /TODAY THROUGH FRIDAY/...
Satellite imagery shows no cloud cover over Western Washington
this morning. ASOS picking up smoke layer between 5000 and 7000
feet. Smoke layer acting like cloud cover keeping temperatures
mild overnight, in the mid 50s to mid 60s at 2 am/09Z.
Upper level ridge over Western Washington through Thursday.
Ridge axis offshore moving over the area Thursday afternoon. In
the lower levels thermally induced surface trough wobbling
between the coast in the overnight hours and inland during the
afternoon. Shallow inversions each morning easily broken by the
daytime heating allowing the smoke aloft to mix down to the
surface. Light northeasterly flow in the lower levels also
pulling in a little wildfire smoke from Eastern Washington and
British Columbia. In addition to the reduced air quality
through Thursday, smoke thick enough to take a few degrees ( 3
to 5 ) off the maximum temperatures both today and Thursday.
Highs in the 80s and lower 90s inland and mid 70s to lower 80s
along the coast. Lows in the 50s and lower 60s. Heat advisory
goes into effect at 10 am/17Z this morning and will remain in
effect through 10 pm/05Z Thursday evening.
Upper level ridge axis shifting east of the Cascades Thursday
night. Low level flow turning weakly onshore. Marine air
filtering into the interior by sunrise but the push is weak
enough where stratus probably not making it east of Puget
Sound. Lows in the 50s and lower 60s.
Weak low level onshore Friday. Even though the upper level ridge
axis is east of the Cascades, 500 mb heights over Western
Washington still in the mid to upper 580 dms. Normally with a
weak marine push scenario would look for high temperatures to
cool by 5 to 10 degrees but with the highs being inhibited
today and Thursday by smoke cooling on Friday will be minimal,
less than 5 degrees for the interior. Highs cooling down along
the coast into the upper 60s to mid 70s. Highs inland in the
upper 70s to upper 80s. If the marine push weakens in future
model runs, heat advisory will need to be extended into Friday.
The weak push also brings into question how much improvement
there will be in air quality Friday. The weaker the push the
more the degraded air quality hangs around. Felton
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Good consistency in the extended models with westerly flow
aloft over Western Washington into the middle of next week.
Upper level low well to the northwest lowering 500 mb heights
over the area to around 580 dms by Monday. Varying degrees of
onshore flow through the period. Stratus developing along the
coast in the evening hours will make a run at Puget Sound each
morning but most likely will fall short. Saturday looks to be
the warmest day with highs in the mid 70s to mid 80s inland and
near 70 coast. Sunday through Tuesday a stretch of normal
temperatures with highs in the 70s and lower 80s inland and mid
to upper 60s coast. Felton
&&
.AVIATION...
An upper level ridge will remain in place over the terminals through
the TAF forecast, with a thermal trough along the coast. Both will
not shift inland until late Thursday/Friday. Winds aloft are light
west or northwest, with surface winds changing from
variable/northeast this morning under 5 kt to north/northwest at 5-
10 kt today. Main concern remains smoke from fires in eastern WA
transiting over the Cascade crest. While an inversion will help
clean up some smoke near the surface this morning, daytime heating
will likely lead to another mixing of smoke down to the surface for
most interior terminals. The highest impacts are likely going to be
from south Puget Sound terminals into the south interior, where
there is a 30-40% chance of MVFR visibilities throughout the day.
The smoke may limit both horizontal and slant-range visibilities.
Additionally, there is also a 40% chance of IFR (20% chance of LIFR)
ceilings for Pacific Coast terminals this morning, where clouds
inland are more likely to be scattered and in VFR.
KSEA...Smoke likely to linger in the TAF period, with the highest
chances of MVFR impacts at the terminal from smoke from 15Z-05Z
Thursday. Outside of this, VFR conditions are generally anticipated
with again some impacts to slant-range visibilities due to the
smoke. Ceilings unlikely to produce impacts this morning. Northeast
winds at 5 kt will shift to the north 5-10 kt in the afternoon.
HPR
&&
.MARINE...
High pressure will remain largely offshore through midweek with a
thermal trough along the coast, that will begin to shift inland
Thursday. Main concern in the short-term remains choppy seas for the
coastal waters, with more seas at 6-8 ft at 6 or 7 seconds likely
today. The current small craft advisory was extended through tonight
with increased confidence in choppy seas, and for the potential for
them to find their way towards the coast. Winds will primarily
remain below small craft criteria, but it will likely get breezy in
the outer coastal waters today with gusts approaching 20 kt. A
trough/low pressure system will replace the ridge/thermal trough
Friday into the weekend. This setup will produce diurnal pushes
through the Strait of Juan de Fuca, as well as some breezy northwest
winds for portions of the coastal waters. Stay tuned for updates on
potential impacts with this system going into the weekend.
Seas 4 to 6 ft for the far inner waters, and 6 to 8 ft for the outer
coastal waters with short periods through the end of the week.
Periods are likely to remain short at 6 to 8 seconds into early next
week, with seas ranging from 4 to 6 ft and 6 to 8 ft between the
interior/far outer coastal waters.
HPR
&&
.FIRE WEATHER...
Elevated fire weather concerns across the area the next couple
of days with warm and dry weather. Smoke layer taking a few
degrees off the maximum temperatures which in turn makes for
higher minimum relative humidity values in the afternoon.
Instead of dropping into the teens in the drier locations
minimum RH values staying around 30 percent the next couple of
days. While no significant wind or instability is expected
through Thursday maximum caution over new fire starts still
should be emphasized.
The thermally induced trough will shift into Eastern Washington
Thursday night. Some uncertainty still remains over potential
instability and incoming wind in combination with the eastward
movement of the thermal trough which may briefly promote fire
growth late Thursday into early Friday. Hot and dry conditions
may hold Friday east of the Puget Sound. Increased onshore flow
Saturday into Sunday is expected to bring cooler temperatures
and increased moisture with healthier humidity recoveries across
the region.
In addition, north to east winds through Thursday will bring in
wildfire smoke from Eastern Washington and British Columbia.
This will cause localized impacts to fire operations at times.
Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory from 10 AM this morning to 10 PM PDT Thursday
for City of Seattle-Downtown Everett / Marysville Area-
Eastern Kitsap County-Eastern Strait of Juan de Fuca-
Eastside-Foothills and Valleys of Central King County-
Foothills and Valleys of Pierce and Southern King
Counties-Foothills and Valleys of Snohomish and Northern
King Counties-Foothills and Valleys of Thurston and Lewis
Counties-Foothills and Valleys of the North Cascades-
Foothills of the Western and Southern Olympic Peninsula-
Island County-Lake Crescent Area Including US 101-Lower
Chehalis River Valley-Lowlands of Lewis and Southern
Thurston Counties-Lowlands of Pierce and Southern King
Counties-Lowlands of Western Skagit and Northwestern
Snohomish Counties-Lowlands of Western Whatcom County-
Middle Chehalis River Valley-Northern Hood Canal-Olympia
and Southern Puget Sound-Port Townsend Area-San Juan
County-Shoreline / Lynnwood / South Everett Area-Southern
Hood Canal-Willapa and Black Hills.
Air Quality Alert until 5 PM PDT Thursday for Cascades of
Pierce and Lewis Counties-Cascades of Snohomish and
Northern King Counties-Cascades of Southern King County-
Cascades of Whatcom and Skagit Counties-City of Seattle-
Downtown Everett / Marysville Area-Eastern Kitsap County-
Eastside-Foothills and Valleys of Central King County-
Foothills and Valleys of Pierce and Southern King
Counties-Foothills and Valleys of Snohomish and Northern
King Counties-Foothills and Valleys of Thurston and Lewis
Counties-Foothills and Valleys of the North Cascades-
Foothills of the Western and Southern Olympic Peninsula-
Grays Harbor County Coast-Lower Chehalis River Valley-
Lowlands of Lewis and Southern Thurston Counties-Lowlands
of Pierce and Southern King Counties-Lowlands of Western
Skagit and Northwestern Snohomish Counties-Lowlands of
Western Whatcom County-Middle Chehalis River Valley-
Northern Hood Canal-Olympia and Southern Puget Sound-
Olympics-Shoreline / Lynnwood / South Everett Area-
Southern Hood Canal-Willapa and Black Hills.
PZ...Small Craft Advisory until 2 AM PDT Thursday 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.
&&
$$
NWS SEW Office Area Forecast Discussion