Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
215
FXUS66 KSEW 240323
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
824 PM PDT Tue Jun 23 2026
.SYNOPSIS...
Upper level ridge & surface trough will shift east of the
Cascades tonight. Well-above average temperatures for one more
day on Wednesday. Then, the pattern is forecast to trend cooler
and wetter Thursday and beyond along with a chance (20-30%) of
thunderstorms on Friday.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
An upper-ridge and thermal surface trough have worked in tandem
to bring another day of well-above average temperatures. Tonight,
these features are slated to gently progress east of the
Cascades. This movement will be the start of a pattern change
across western Washington with increasing onshore flow. As a
result, conditions will begin to trend cooler but we`ll see one
more warm day. Overnight lows are forecast to bottom into the
upper 50s to lower 60s.
As mentioned, another warm day is in the forecast across the
interior on Wednesday. Minor HeatRisk is favored to become more
widespread due to increased onshore flow but moderate HeatRisk
will remain for the urban centers. The current Heat Advisory
should be allowed to expire for coastal adjacent areas Tuesday
night and the remainder of the area on Wednesday night. Onshore
flow is favored to peak in intensity Wednesday evening as
widespread marine air intrusion takes hold. Areas of marine
stratus looks to develop as well. REFS is indicating a 30-40%
chance of wind gusts greater than 35 mph across Whidbey Island
during this time. HREF probs are more bullish with 50-60%
chance. Overnight lows are to bottom in the lower to upper 50s
Thursday will feel more like late June with 60s along the coast
and lower 70s throughout the interior. Morning stratus will
lessen in coverage but mid-high level clouds are forecast to
increase ahead of an approaching frontal system. Rainfall looks
to arrive along the coast Thursday evening before spreading
inland overnight then transitioning to post-frontal showers.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As mentioned, post-frontal showers in store for Friday along
with a developing convergence zone. NBM is highlighting a
20-30% chance of thunderstorms as the airmass is somewhat
unstable. Cool upper level low dropping down over the area
Friday night into Saturday keeping showers in the forecast. Weak
upper level ridge building offshore Sunday. Weak upper level
trough moving down the backside of the ridge into Western
Washington Monday for a chance of showers.
High temperatures in the upper 50s to mid 60s Friday and
Saturday and only in the 60s Sunday and Monday. There is a
chance for record low maximum temperatures Friday and possibly
Saturday.
&&
.AVIATION...
VFR conditions area-wide this evening with some scattered mid to
high clouds present. Life under the ridge should keep clouds over
much of the area relegated to the higher levels...although HQM may
experience MVFR to IFR conditions overnight/early Wednesday morning
due to marine stratus. Latest model data fairly confident in this
outcome, but current satellite imagery shows any nearby low clouds
to be well south of the area off the OR coast. Given this
discrepancy between models and current reality, opted to cover these
lower cigs with a TEMPO instead. If any lower cigs do occur, they
are expected to burn off by noon tomorrow. North to northwesterly
winds this evening generally ranging 4-8 kts. Some terminals have
already gone light and variable and most locations are expected to
do the same overnight. The exception is HQM, where westerly winds
currently running 10-15 kts. These will ease late tonight, dipping
down to 4-8 kts before ramping back up again to 10-15 kts by
Wednesday afternoon.
KSEA...VFR expected through the TAF period. Northwest winds 4-8
knots this evening, becoming light and variable overnight. A return
of broader onshore flow on Wednesday will shift winds to the west-
southwest sometime Wednesday morning between 12-16Z and remaining
there for the remainder of the TAF period as speeds return to 4-8
kts.
18
&&
.MARINE...
A thermal surface trough will progress east of the Cascades
tonight. Here, low-level onshore flow will begin to increase
across area waters. A gale watch remains for the Central and
Eastern Strait of Juan de Fuca for Wednesday night. Onshore
gradients easing Thursday. Frontal system moving through the
waters Friday with possible small craft advisory winds with and
just behind the front. Winds easing Saturday.
Choppy seas developing over the outer coastal waters tonight
with swell 7 to 10 feet with a 7 to 9 second period. As a result
a SCA remains for these zones in particular. The choppy seas
will continue over the outer coastal waters through Wednesday
night.
&&
.FIRE WEATHER...
An upper-ridge is progressing gently across the
region. As a result, very warm and dry weather has lead to
elevated fire weather conditions for Wednesday. Min RHs will bottom
around the 20-25% range for isolated areas of the Cascade valleys.
Onshore will increase on Thursday with widespread marine air
intrusion. Fire weather concerns will alleviate Thursday onward as
wetting rains return Thursday night into Friday. A cooler and
wetter pattern is favored into early next week.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 11 PM PDT this evening for Eastern Strait
of Juan de Fuca-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-Lower Chehalis River Valley-
Lowlands of Lewis and Southern Thurston 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-Southern Hood
Canal-Willapa and Black Hills.
Heat Advisory until 11 PM PDT Wednesday 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-Lowlands of Pierce and Southern King
Counties-Shoreline / Lynnwood / South Everett Area.
PZ...Gale Watch from Wednesday evening through late Wednesday night
for Central U.S. Waters Strait Of Juan De Fuca-East
Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory until 6 AM PDT Thursday for Coastal
Waters From Cape Flattery To James Island 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville 10 To
60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater 10 To 60 Nm.
&&
$$
NWS SEW Office Area Forecast Discussion