Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
694
FXUS66 KSEW 151028
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
328 AM PDT Mon Jun 15 2026
.SYNOPSIS...Upper level ridge over the area today weakening
tonight through Tuesday. Thermally induced surface trough over
the interior will shift east of the Cascades tonight. Record
high temperatures today inland. Increasing low level onshore
flow tonight with much cooler weather Tuesday. Low level
onshore flow pattern continuing through Wednesday. Upper level
ridge rebuilding Thursday with weak low level onshore flow.
Little change in the pattern Friday through the weekend.
&&
.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Satellite imagery shows weather system moving inland over
British Columbia well north of Western Washington. High clouds
associated with the system beginning to move over the northern
portion of the area. Clear skies elsewhere. Temperatures at 3
am/10z were in the mid 50s to near 70.
Thermally induced surface trough over the interior today for one
more round of record high temperatures. Highs along the coast
peaking midday as afternoon seabreezes kick in with the thermal
trough inland. System moving by well to the north will spread
high clouds over the area. Highs over the interior in the 80s to
mid 90s. Highs along the coast in the 70s and lower 80s.
Thermally induced surface trough moving east of the Cascades
tonight with the low level flow going onshore. This will
eventually bring cooler marine air into the interior by Tuesday
morning. Because of this the heat advisory will come to an end
at 5 am/12z Tuesday morning. Stratus developing along the coast
overnight getting as far inland as the South Puget Sound by
sunrise. Lows tonight in the mid 50s to lower 60s.
Much cooler Tuesday as the upper level ridge overhead weakens
with low level onshore flow. Surface analysis has ridge axis to
the south of the area. This is an indicator of a stronger marine
push cooling high temperatures as much as 20 degrees versus the
highs Monday. Highs in the mid 60s to mid 70s.
Little change in the pattern Tuesday night into Wednesday. Low
level onshore flow continuing with a flat upper level ridge over
the area. Stratus along the coast moving inland overnight
getting close to the Puget Sound by morning before retreating
back to the coastline. Lows in the upper 40s to mid 50s. Highs
in the 60s on the coast and upper 60s to upper 70s inland.
Felton
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Upper level ridge rebuilding slightly Wednesday night into
Friday with weakening low level onshore flow. Highs a little
warmer Thursday, in the upper 60s to mid 70s coast and 70s to
lower 80s inland. Slight warming trend continuing Friday highs
in the 70s to mid 80s over the interior. Afternoon seabreezes
along the coast keeping highs there in the 60s and lower 70s.
Flat upper level ridge over the area for the weekend. A few more
ensemble solutions indicating stronger onshore flow then the
current blend forecast is showing. Will stay with the idea of
highs in the mid 70s to lower 80s for the interior and 60s on
the coast both days of the weekend. If the model trends continue
look for the forecast highs inland to be cooler in future
forecast packages.
&&
.AVIATION...
High pressure centered offshore in the Pacific will allow for
dry conditions to continue across western Washington. High
level clouds can be seen on infrared satellite imagery moving
in from British Columbia; these clouds will be in place through
the morning and afternoon hours before clearing out this
evening. VFR conditions persist through the TAF period.
Northerly winds will be less than 5 kts today, shifting to
becoming northeast/east and increasing to around 5 to 10 kts
this evening and into Tuesday.
KSEA...VFR conditions prevail through the TAF period with high
clouds expected throughout the day. Northerly winds around 5 kts
ease to be calm this morning. Winds then pick up again from the
east around 10 kts late this evening into early Tuesday
morning.
&&
.MARINE...
A thermal trough continues to shift inland this morning,
which will allow for onshore flow to begin later this afternoon
and evening. A strong marine push will occur for the central and
eastern portions of the Strait of Juan de Fuca tonight through
Tuesday night. West winds will increase this afternoon and
evening to 15 to 25 kt, then then further increase on Tuesday
for a period of gale force winds Tuesday afternoon and evening
with gusts up to 40 kts. Winds begin to decrease through the
Strait late Tuesday.
Northwesterly winds will increase through the coastal waters
beginning Tuesday and lasting through the rest of the week for
an extended period of Small Craft Advisory conditions. Seas will
also become locally wind-driven and become very steep. Waves
will increase Tuesday night into Wednesday up to 10 to 12 ft
with a dominant wave period of around 9 to 10 seconds.
&&
.FIRE WEATHER...
Record high temperatures with dry conditions in the lower levels
today. Daytime minimum relative humidity values below 20%
across much of Southwest Washington and the Southern Cascades
and below 30% elsewhere. Even though fine fuels have not
reached critical thresholds, this dry of an air mass will create
elevated fire concerns especially for dry grassy areas, as well
as piles of dead fuels. Relative humidities improve with the
return of onshore flow tonight into Tuesday easing fire weather
concerns into the middle of the week. 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. Fuels will continue to slowly dry with no precipitation
forecast through the weekend. Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 5 AM PDT Tuesday 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.
PZ...Small Craft Advisory from 1 PM this afternoon to 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.
&&
$$
NWS SEW Office Area Forecast Discussion