Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
147
FXUS66 KSEW 152155
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
255 PM PDT Mon Jun 15 2026
.SYNOPSIS...
Increasing onshore flow will promote cooler and more moist
conditions across the area Tuesday and Wednesday. Upper level
ridge rebuilding Thursday with weak low level onshore flow will
allow temps to start to warm again. Little change in the
pattern Friday through the weekend though with greater
uncertainty.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Very warm conditions continue across much of western Washington
this afternoon, despite the development of high clouds across
the area. Farther north, however, thicker coverage of high
clouds as well as developing onshore flow has helped keep their
temperatures relatively cooler, with temps in the 60s and 70s,
compared to upper 80s and low 90s from metro Seattle and
southward. Areas along the coast will peak in the 70s and low
80s with developing onshore flow already this afternoon.
Pressure rises along the coast show that the thermal trough has
shifted inland and will work its way east of the Cascades
tonight. Onshore flow will continue to strengthen tonight, which
will allow low temperatures to cool slightly compared to
yesterday. Lows will range from the mid 50s to around 60 in the
urban metro. The heat advisory will therefore expire tomorrow
morning at 5 AM.
Stronger onshore flow will continue through much of the day on
Tuesday. This will allow for temperatures to moderate up to
15-20 degrees compared to today, with highs in the 60s along
the coast under marine stratus, and low to mid 70s across the
interior. It will be noticeably breezy across much of the area,
with the strongest winds expected through the Chehalis gap and
the Strait of Juan de Fuca. Gusts 25-35 mph will be possible in
these areas, up to 15-25 mph elsewhere. Expect a convergence
zone to develop over the Puget Sound lowlands, but no
precipitation is expected out of this. As winds decrease Tuesday
night, this will allow for even cooler lows, down to the upper
40s to mid 50s.
Similar conditions on Wednesday; more stratus for the coast and
west of Puget Sound but will burn off throughout the day. Highs
in the upper 60s on the coast, with most of the interior in the
70s to near 80 in the Southwest Interior.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Zonal flow will become more northwesterly as an upper level
ridge begins to build offshore. This will allow for temperatures
to start another brief warming trend Thursday and peaking on
Friday. Highs look to top out in the upper 70s to upper 80s,
with the warmest temperatures across the Southwest Interior.
This will correlate to a Moderate level of HeatRisk on Friday
for areas around the Seattle metro.
The range in uncertainty increases Saturday into early next week
in terms of temperatures as the pattern gets more convoluted.
The ridge remains onshore, with several shortwaves potentially
moving through across the Pacific Northwest and a broad low
moving into California. Then, a trough moves across from the
north this weekend from B.C. into northeast Washington.
Solutions without some of the shortwaves keep us warmer with
weaker onshore flow; those with waves allow for stronger pushes
and more moderate temperatures. The wave moving in from B.C. may
allow for more unstable conditions to develop over the Cascades
with very slight (15%) chances for showers and thunderstorms
over the weekend. The National Blend is trending towards warmer
solutions with highs in the mid 70s to low 80s.
62
&&
.AVIATION...
West to northwest flow aloft will continue into Tuesday as an upper
ridge over the region weakens in response to a weak upper trough
moving onshore across British Columbia. Increasing low level onshore
flow will likely bring MVFR ceilings to the coastal areas late
tonight with VFR continuing across much of the interior. Gusty
westerly surface winds can be expected near the coast as well as in
and adjacent to the Strait of Juan de Fuca.
KSEA...VFR with variable amounts of high level moisture. Surface
winds light west to northwesterly will back to southwesterly this
evening and rise to 8 to 12 knots toward mid-morning Tuesday.
27
&&
.MARINE...
Onshore flow has resumed over the coastal waters as the thermal
trough has progressed inland. Northwesterly winds will increase
late tonight into Tuesday over the coastal waters, reaching
Small Craft Advisory conditions by mid-day Tuesday. These windy
conditions will persist through the rest of the week. Seas will
become locally-wind driven and become very steep. Wave heights
will increase throughout the day Tuesday up to 10 to 13 ft with
a dominant period of around 10 seconds. Waves in the outermost
waters may reach up to 15 ft by late week.
Winds are beginning to strengthen through the Strait of Juan de
Fuca at present and will continue to do so tonight, up to gale
force for much of the day on Tuesday. Small Craft Advisory winds
will also funnel down into Admiralty Inlet by Tuesday afternoon.
Winds look to ease Tuesday night.
62
&&
.FIRE WEATHER...
Strengthening onshore flow tonight into tomorrow will help to
bring more moisture and cooler temperatures, easing fire weather
concerns. Conditions dry out a bit again Thursday and Friday
with minimum relative humidity values dropping into the 25-35%
range despite no low level offshore flow. Temperatures will rise
back into the upper 70s to low 80s in the lowlands. Breezy
northerlies in the lowlands as well as westerly flow through the
Cascades may pose elevated fire weather risks Thursday and
Friday. Fuels will continue to slowly dry with no precipitation
forecast through the weekend.
62
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 5 AM PDT Tuesday for 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-
Lower Chehalis River Valley-Lowlands of Lewis and
Southern Thurston Counties-Lowlands of Pierce and
Southern King Counties-Middle Chehalis River Valley-
Northern Hood Canal-Olympia and Southern Puget Sound-
Shoreline / Lynnwood / South Everett Area-Southern Hood
Canal-Willapa and Black Hills.
PZ...Small Craft Advisory until 11 PM PDT this evening for Central
U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
Waters Strait Of Juan De Fuca.
Gale Warning from 11 PM this evening to 11 PM PDT Tuesday for
Central U.S. Waters Strait Of Juan De Fuca-East Entrance
U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 2 PM to 11 PM PDT Tuesday for
Admiralty Inlet.
Small Craft Advisory from 11 AM Tuesday to 5 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