Washington State Forecast Discussion

Western Washington


108
FXUS66 KSEW 170911
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
211 AM PDT Thu Apr 17 2025

.SYNOPSIS...An upper ridge will continue to bring drier, warmer
weather for Western Washington through Friday. A weakening frontal
system will move through on Saturday. Troughing will develop
across the Pacific Northwest Sunday into Monday for continued
unsettled weather. Weak ridging will build midweek.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...Clear skies across Western
Washington this morning with an upper ridge located offshore.
Northerly flow will continue through today, albeit at a lesser
magnitude than on Wednesday. Highs today will be in the 60s. The
ridge axis will then move over Western Washington on Friday. This
will allow for temperatures to warm a few degrees further, with
highs in the mid 60s to low 70s for most areas.

Increasing onshore flow Friday night ahead of a weakening frontal
system that will move across the area into Saturday.
Precipitation chances will increase later Friday night into
Saturday with this front, although amounts are generally expected
to be light, less than 0.10" for most areas during this period.
Lingering showers are expected Saturday evening into Saturday
night, especially for the Cascades, as well as favored convergence
zone area in the central Puget Sound. Temperatures will cool for
Saturday, with highs only reaching the 50s for most areas.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Troughing will be
reinforced Sunday into Monday across the Pacific Northwest. This
will result in continued shower chances, peaking Sunday afternoon
into Sunday evening. Snow levels will also lower Sunday night into
Monday to near 2500 to 3000 feet, resulting in the potential for
snow showers over the Cascades in any convergence zone that
develops over King and Snohomish Counties. Ensembles then suggest
weak ridging tries to build again offshore, resulting in generally
drier conditions Tuesday and Wednesday. However, some uncertainty
remains in ensembles in regards to the extent ridging builds into
Western Washington. Temperatures will remain cooler early next
week, and will have to monitor any frost concerns on Wednesday
morning. Highs will be in the 50s Sunday and Monday, with a slow
warming trend into mid week. JD

&&

.AVIATION...An upper level ridge will build into the British
Columbia coast today producing northerly flow aloft over Western
Washington. The air mass remains dry and stable with generally
northerly surface winds. With little moisture to work with within
the airmass, widespread VFR conditions are expected for all
terminals throughout the TAF period.

KSEA...Clear skies. Surface winds northeasterly 6 to 10 knots this
morning before shifting more northwesterly after 18Z. Speeds are
expected to remain similar with the shift in direction. A return to
northeasterly winds with speeds easing to 4 to 8 knots is expected
Thursday evening and into the overnight.

18

&&

.MARINE...Surface ridging will remain over the waters into Friday. A
weak front and associated trough will slip southward along the
British Columbia and into the area Friday night into Saturday. This
will initiate an increase in onshore flow with likely headlines and
possible gales in the central/east strait. A secondary system will
produce a similar result later Sunday into early Monday. High
pressure will then rebuild across the waters early next week.

Seas mostly 5 to 7 ft although right along the coast and in the west
Strait lower wave heights can be expected. These conditions will
persist into Friday before building back above 10 feet early in the
weekend. 27/18

&&

.HYDROLOGY...No river flooding is expected over the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT early this morning 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.

&&