Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
645
FXUS66 KSEW 250426
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
926 PM PDT Wed Jun 24 2026
.UPDATE...
Showers and thunderstorms have subsided this evening as solar
forcing wanes. Now, the anticipated cool down has begun as low-
level onshore strengthens. Satellite imagery shows marine
stratus marching stretching along the coast and marching inland
as areas across W WA wake up to mostly cloudy skies Thursday
morning. Low temps are forecast to the lower to upper 50s. The
previous discussion is below along with an updated aviation
section:
&&
.SYNOPSIS...
An upper level ridge and thermal trough will begin
to move inland today into Thursday. Onshore flow will begin to
increase tonight into Thursday, bringing in some clouds in the
morning, as well as much cooler temperatures. A frontal system
will move across the region late Thursday into Friday, with
widespread beneficial rain showers, and also the chance of
isolated thunderstorms, especially with a post frontal
convergence zone Friday afternoon north of Seattle. Breezy
southwest winds Friday afternoon with gusts up to 25 mph are
also likely. The pattern remains unsettled this weekend going
into next week.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
Main sensible weather concerns include revolve around lightning
chances and heat today followed by unsettled weather tomorrow
afternoon onward.
Latest day cloud phase RGB show increasing building with
glaciating cloud tops in the northeast Olympics. Latest GLM and
ground-based networks showed a few flashes/strikes over the last
hour. Regional radar mosaic depicts greater coverage and
convective activity along the upper eastern slopes of the WA
Cascades. Current water vapor shows a shortwave trough ejecting
into western WA at the base of the upper low located in the Gulf
of AK.
Marginal instability in place late this morning with MUCAPEs >
500 J/kg per SPC mesoanalysis that aligns with current REFS
soundings in the non-mountain areas of the sound and eastern
Olympics. Current thinking is there will be potential for a few
strikes this afternoon in the northeastern Olympics with main
hindrance initially revolving around the dry air in the lower
levels that needs to be overcome. Latest SPC mesoanalysis shows
low RH within LCL-LFC, and similarly see this drier air in REFS
soundings that will contribute to dry air entrainment. This
seems most likely given how the initial updrafts/cell weaken. As
such, best window for any lightning most likely within the
window this afternoon from 2pm-7pm for cells/lightning chances
from additional moistening from repeated cells/failed CI. Low
confidence in crossing the sound at this time and reaching the
I-5 corridor but bears monitoring with confidence 10-20% based
on REFS, NBM, and last 4-5 HRRR runs. Current analysis supports
the best chances for any lightning in the I-5 corridor being
along far western Snohomish (albeit low chances).
Otherwise, today will be the last day of hot temperatures with
highs 15-20 F above average and near certain moderate HeatRisk
along western Pierce-King-Snohomish and far eastern Olympics.
Cooling trend starts tomorrow with highs forecast 15-20 F cooler
than today, except around 10 F cooler along the western
Olympics. An initial weak marine push anticipated late
afternoon/early tonight with a stronger push late
tomorrow/tomorrow night with reinforcing onshore flow Friday as
the main low drops to Vancouver Island by Friday. This will
setup an unsettled pattern late Thursday night to Friday night
as the low meanders southward along the offshore the WA Coast.
Initial rain chances ramp-up along the Olympics by 5 pm Thursday
spreading east to the sound and westward Cascade slopes 5pm-11pm
PDT Thursday (chances for 0.01 or more 50-70% based on the
REFS). On Friday, marginally instability in place will promote
15-20% chances for lightning across the Sound-western slopes of
the WA Cascades with lesser thunder chances over the Olympics
and west. 24-hr LPMM ending Friday afternoon (00Z) show 0.5 to
1.25 inches along the foothills and westward slopes of the
central and Northern WA cascades and up to 1 inch in the western
Olympics.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The large scale pattern early Saturday will be characterized by
a mid-level low over WA that will be slowly evolving east
across the Northern Intermountain West to northern Rockies by
Sunday. This evolution will continue to keep highs reading
cooler than normal, around 4-8 F., this weekend. Well offshore
upper-level ridge will be building behind this feature in the
eastern North Pacific with mean forecast ECMWF EPS heights
exceeding the 90th %tile. Strong signal for moderate winds
within the Strait of Juan de Fuca with hourly probabilities
showing enhanced chances for 22 kts or higher, 30-60%, Saturday-
Saturday night with 50th percentile peak daily gusts, most
likely outcome, around 30 kts. While lowlands and non-mountain
areas will start to see chances taper off Saturday, chances will
remain elevated in the Olympics and westward slopes into early
next week under northwest flow. Elsewhere, low chances will
prevail in the interior non-mountain areas through Wednesday
(generally 5-15%).
A modest uptick in temperatures by mid-week, albeit with highs
still reading 2-6 F below average, with overnight lows reading
near average for this time of year.
ET
&&
.AVIATION...
Onshore flow has started to infiltrate the coastal terminals with
MVFR conditions. Onshore flow is expected to continue though the
night and into Thursday. MVFR probabilities for the interior 15-60%
from 11Z-18Z Thursday while the coast has IFR probabilities of 10-
30% through 18Z Thursday. Winds will remain out of the southwest 5-
12 kt, except for near the Strait of Juan de Fuca where winds will
be 10-15 kts with gusts up to 25-30 kts through 20z Thursday. A cold
front will move through late Thursday, introducing shower chances as
early as 18Z for the coast and widespread shower chances by 03Z
Friday.
KSEA...VFR through tonight. There is a 15-35% chance of MVFR stratus
reaching the terminal between 12-18Z this morning, which will lift
up to VFR later in the day (but remain broken or overcast). Shower
chances will increase beginning at 00Z Friday onwards, bringing MVFR
conditions. Winds expected to remain out of the southwest at 5-10kt
through most of the period. West/southwest winds will pick up after
00Z Friday with gusts up to 20 kts.
HPR
&&
.MARINE...
Higher pressure offshore will continue with lower pressure inland
through tonight as a surface thermal trough continues to move
inland. A strong onshore push tonight remains on track to produce
gales in the central/east Strait of Juan de Fuca, as well as gusty
winds over 20 kt in the Admiralty Inlet (with a small craft advisory
there adjacent to the gale warnings). Seas and winds this afternoon
have decreased in the coastal waters, which resulted in the small
craft advisory being cancelled early. A cold/occluded front will
push through the waters tonight into Friday, with widespread rain
showers and also a 20% chance of thunder Friday afternoon for the
interior waters. Ensembles maintain a high likelihood of widespread
wind gusts over 20 kt going into Friday with the front. The
unsettled onshore pattern likely continues into the weekend into
next week, with winds at times remaining breezy for outer portions
of the coastal waters, as well as the Strait of Juan de Fuca.
Seas decreasing to 4-6 ft today, and will hold around 4-6 ft through
Saturday before increasing to 6-8 ft and 8-10 ft this weekend into
next week.
HPR
&&
.FIRE WEATHER...
Elevated fire weather concerns focused along
WAZ654 and WAZ655, with non-mountain areas seeing min RHs in
the teens yesterday, and in areas of the west slopes. While a
slight uptick in RH is anticipated today, min RH forecast in
mid-upper 20 percent across lower elevations. Meantime, this
will occur in tandem with sustained winds 10 mph and higher.
Latest NBM shows joint probabilities 60-80% that further
increases confidence for this RH-wind combination. Locations of
the west slopes of the central Cascades are also seeing gusts
approach 20 mph with RH under 30%.
Looking ahead, cooler and wetter conditions will prevail
tomorrow night-Saturday night that will limit fire weather
concerns. However, the unsettled pattern will yield isolated,
infrequent lightning threat on Friday with the chance of
thunder around 15-20% across the sound to the west slopes of
the WA Cascades.
ET
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 11 PM PDT this evening 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 Warning until 6 AM PDT Thursday 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 Admiralty
Inlet.
&&
$$
NWS SEW Office Area Forecast Discussion