Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
261
FXUS66 KSEW 050244
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
744 PM PDT Tue Aug 4 2026
.SYNOPSIS...
Dry and hot conditions through Thursday as an upper level ridge
moves over Western Washington. A thermal trough over the coast will
bring offshore winds at times. Onshore flow returns late in the
week as the thermal trough pushes inland late Thursday. Cooler
conditions return this weekend.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
The latest forecast remains on track this evening, with an
updated aviation section below. Smokey skies across Western
Washington this evening from fires in British Columbia and
Eastern Washington impacting visibility and air quality. Latest
HRRR smoke guidance suggests high near- surface smoke
concentrations will continue to filter into Western Washington
this evening and overnight. For the latest information and air
quality please refer to your local clean air agency.
Warmer conditions anticipated as an upper level ridge offshore
prepares to move inland across Western Washington Wednesday into
Thursday. High temperatures will peak in the 70s along the coast and
mid 80s to mid 90s as the ridge axis is directly over the region.
This will result in Moderate HeatRisk for the majority of the
region, for which a Heat Advisory has been issued. In addition, warm
temperatures overnight will bring bring limited relief for interior
locations, especially for urban heat islands. The ridge axis will
move away from the region, weaken and move into Eastern Washington
late Thursday night.
Offshore flow will continue at times through Thursday with a thermal
trough along the coastline. This will keep advecting smoke into the
region. The thermal trough is expected to move inland later on
Thursday, marking the return for onshore flow, which should
ameliorate smokey conditions.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Onshore flow is favored late in the week and should help improve
smoke conditions. However, uncertainty remains on how quick this
improvement will be as it will be dependent on the strength of
the winds. Zonal flow will develop over Western Washington late
this week and into the weekend. This will help moderate
temperatures across the region to the 60s along the coast and
mid 70s to low 80s in the interior. By Monday, there is good
agreement between ensemble that a weak upper trough will settle
over the region.
29
&&
.AVIATION...
Northwesterly flow aloft as upper level ridging continues offshore.
Surface wind direction mostly northerly, although some terminals
remain easterly this evening. Speeds are pretty uniform across the
area, generally ranging 5-10 kts. Most locations should see a shift
to north or northeasterly tonight before becoming light and variable
overnight.
Majority of terminals reporting VFR conditions however widespread
smoke in place over W WA has allowed some locations to dip down into
MVFR conditions at times. This drop in conditions due mainly to vis
restrictions imposed by smoke as opposed to any cigs or smoke layer.
Vis should rebound somewhat to around 6SM tonight for most locations
as the atmosphere decouples and smoke becomes more of an aloft
feature with the main impact being continued hazy conditions. That
said, it is important to remember that any smoke may limit both
horizontal and slant-range vis, therefore, experienced vis may be
less than what is being reported in observations. The problem of
surface-based smoke will return for Wednesday afternoon at a level
similar to today.
KSEA...Visibility impacts present but so far have not dipped below
6SM. Will limit vis reductions to this for 06Z issuance unless obs
dictate otherwise. Still worth noting that brief dips down to 4SM
remain possible this evening and early tonight. Also, refer to above
statement regarding slant-range vis. Have also accounted for smoke
likely playing a role in ASOS cig of OVC between 040 and 050. This
should dissipate tonight as atmosphere decouples, relegating smoke
to higher levels. Latest smoke model guidance suggests Wednesday
being very similar to today.
18
&&
.MARINE...
A strong area of high pressure will remain offshore throughout
midweek as a thermally induced low pressure expands northward along
the interior coast. Northwesterly winds will prevail across the
coastal waters this week. With increasing confidence, a small craft
advisory has been issued for the southernmost coastal water zones
this afternoon. Breezy conditions briefly expected Tuesday morning
across Puget Sound, however winds should remain below small craft
thresholds. The surface trough is expected to push inland on
Thursday, resulting in increased onshore flow across the waters.
Small craft winds are possible through the Strait of Juan de Fuca as
early as Thursday evening, continuing into the weekend. Latest
guidance suggests the strongest winds will be on Friday, with a 70-
85% chance of small craft winds and 25-40% chance for gales. Another
strong push expected on Saturday, with a 65-80% chance for small
craft winds and 15-20% chance for gales.
Seas expected to remain below 10 ft for the majority of week and
will trend toward 10 feet toward the weekend. Steep seas possible
Tuesday evening at times over the coastal waters.
29
&&
.FIRE WEATHER...
A warming and drying trend will continue across western Washington
through the week as a high pressure ridge builds offshore and a
surface thermal trough builds northward along the Pacific coast.
Several days of drying and warming will continue to drive minimum
relative humidity values to near critical levels, especially in the
western Cascades and Olympics where humidities may reach critical
values as low as the teens to upper single digits by Wednesday and
Thursday. While no significant wind or instability is expected
through the week, maximum caution over new fire starts should be
emphasized.
The thermal trough will shift inland later on Thursday with the
arrival of a frontal system late Thursday into Friday. 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 on on Friday east of the
Puget Sound, though increased onshore flow by Saturday is expected
to bring cooler temperatures and increased moisture with healthier
humidity recoveries across the region.
In addition, north to east winds throughout the week will continue
to bring in wildfire smoke from eastern Washington and British
Columbia. This will cause localized impacts to fire operations at
times.
15
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory from 10 AM Wednesday 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 Wednesday 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