Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
831
FXUS66 KSEW 220342
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
842 PM PDT Tue Apr 21 2026
.SYNOPSIS...A return to cooler and cloudier conditions as
showers rotate through the region around an upper low to the
south. Drier and warmer conditions return late in the week
through next weekend with a stronger ridge of high pressure
building offshore.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...Localized showers
at times across western Washington this evening with an upper
low positioned offshore of southern Oregon and northern
California. Clouds and rain at times into Wednesday morning. No
major forecast updates this evening, previous discussion below.
An upper low remains positioned off of southern Oregon and
northern California, spreading increasing cloud cover and mid
level moisture across the region. We`ll see continued showers
across the region, with increasing coverage across Western
Washington. This will bring temperatures down to considerably
cooler values than the last few days. With increasing
instability this afternoon, we`ll have the potential for a few
isolated thunderstorms across the Cascades through the evening
hours. Little change to the pattern into Wednesday as the upper
low slowly progresses eastward across the western U.S.
Temperatures remain on the cooler side, toping out mostly in the
upper 50s tomorrow. Moving into Thursday, heights begin to rise
on the back side of the system as the upper low drifts further
eastward. This will have the impact of both cutting off support
for additional showers and bring about another warming trend as
clouds begin to decrease.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...Ensemble guidance remains
in good agreement for a return of high pressure over the region
late in the week. This should bring a return of Minor HeatRisk
as temperatures again climb into the upper 60s to near 70 in the
warmest locations. However, the location of the ridge axis -
specifically, how far offshore or over the region it remains -
remains a key bit of uncertainty in the forecast with a decent
amount of spread. This could leave the door open to the
opportunities for some light showers late in the weekend or
early next week with a few embedded impulses rotating within the
flow across the region.
&&
.AVIATION...South to southeasterly flow aloft will turn east to
northeasterly tonight as a broad upper trough moves onshore
over northern California and southwest Oregon. The low level
flow is onshore. Ceilings are deteriorating this evening as
moisture associated with the area of low pressure spreads
northward into the region. MVFR ceilings in scattered showers
are expected most areas with shower coverage increasing
overnight. Predominantly MVFR ceilings in showers will persist
into Wednesday with minor improvement late in the day as shower
activity diminishes.
KSEA...MVFR ceilings in showers this evening will continue into
Wednesday morning with improvement to low end VFR expected near or
after 00Z Thursday. Surface winds S/SW 8 to 12 knots this
afternoon/evening will increase Wednesday morning to 10 to 15 knots
gusting to around 20 knots at times.
27/41
&&
.MARINE...Weak low pressure will remain over the inner coastal
and interior waters into Thursday with broad high pressure
remaining well offshore for an onshore flow pattern. The flow
will turn more northerly over area waters Friday into Saturday
with a broad surface ridge over the western Canadian provinces
and lower pressure over the Pacific Northwest.
Small craft advisories remain in effect for the central/east
strait today and for the coastal waters and Puget Sound
tomorrow. Seas will build and steepen over the coastal waters on
Wednesday with seas nearing rough bar criteria at Grays Harbor
by Wednesday night. Seas will then gradually subside later
Thursday into the weekend.
27
&&
.HYDROLOGY...No river flooding is expected during the next seven
days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
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.
Small Craft Advisory from 4 AM to 8 PM PDT Wednesday for Puget
Sound and Hood Canal.
Small Craft Advisory from 11 AM Wednesday to 11 AM PDT
Thursday 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