130
FXUS66 KSEW 270323
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
820 PM PDT Fri Jul 26 2024

.SYNOPSIS...A weak upper level trough remains over western
Washington through the weekend. A passing front Monday will bring
widespread rain chances to the area, with showers lingering into
Tuesday as the upper trough moves through. Weak high pressure aloft
begins to build again toward midweek.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...Fair skies over W WA this
evening with some high clouds drifting over the area. Already seeing
some 50s emerging along the coast, however the majority of the area
seeing temps generally in the 60s...save for urban heat islands such
as the Seattle metro area, which is still reporting temps in the
lower 70s. Overall a fairly quiet evening. Inherited forecast looks
on track and see no need for any evening updates. For additional
forecast details, please refer to the Previous Discussion section
below.

18

From Previous Discussion...Weak upper level troughing over the
region this weekend for generally mild conditions.
Temperatures will be close to late July normals. There is a slight
chance of showers in the North Cascades (near the crest) Saturday
afternoon, otherwise the remainder of western WA will be dry.

A deeper trough taps into some moisture over the Pacific on Monday
for wetter and cooler conditions. Much of western WA will see
measurable rain with this system. Up in the mountains, there`s a
50-70% chance of seeing wetting rains (at least 0.25").
Temperatures will be cooler and in the 60s. 33

.LONG TERM /TUESDAY THROUGH FRIDAY/...From Previous
Discussion...Showers linger on Tuesday as the upper level trough
exits east toward Idaho/Montana. Heights will build and we`ll see a
little warming (but still a few degrees shy of normal). Dry and
warmer weather returns mid-week onwards with broad upper level
ridging over the western CONUS. Temperatures on Thursday and Friday
will reach the 80s again (across the interior lowlands) with pockets
of Moderate HeatRisk. NW flow will keep the coast cooler and in the
60s and 70s. 33

&&

.AVIATION...Northwest flow aloft as subtle ridging resides offshore
along with troughing nearby. VFR conditions in place and largely
expected to remain that way for much of the TAF period. It is worth
noting that latest runs are starting to suggest marine stratus
pushing a little further inland when compared to previous runs. The
usual coastal sites and those that tend to favor lower cigs will
likely see MVFR to IFR conditions emerge late tonight into Saturday
morning, however starting to see indications that SEA and PAE may
see lower cigs as well. Have already included a hint to this in the
03Z SEA update but will re-evaluate for the 06Z TAF issuance.
Otherwise, VFR conditions expected to resume by noon Saturday.

KSEA...VFR expected for the remainder of the evening. May see cigs
erode down to low-end VFR/high-end MVFR around or a little after 12Z
Saturday morning. VFR conditions expected to return by 18Z. Surface
winds northerly 6 to 10 kt this evening and tonight before easing
overnight...then becoming more west-southwesterly late Saturday
morning.

McMillian/18

&&

.MARINE...Low-level onshore flow persists with high pressure over
the coastal waters of the Pacific and lower pressure inland. Benign
conditions over the marine zones expected tonight into Saturday. A
westerly push through the strait this evening is seeing wind speeds
largely remain below SCA criteria. Only Race Rocks is currently
meeting criteria and, as such, conditions are not widespread enough
to warrant any headlines or updates. The next best chance for SCA-
level winds in the Strait appears to be Saturday night into Sunday
morning. Marine stratus will persist in varying coverage for the
next several days with visibility restrictions a possibility over
the zones. A frontal system will move through the region early next
week. At this time the threat for widespread breezy winds impacting
small craft is low.

Seas generally 4 to 6 ft tonight into Saturday...although some spots
in the far outer waters may see seas reach 7 ft. Waves easing
Saturday evening with resulting seas 3 to 5 ft.

McMillian/18

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$