875
FXUS66 KSEW 292115
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
215 PM PDT Fri Aug 29 2025

.SYNOPSIS...Upper level ridging will shift eastward by this
evening. An upper level low off the coast will influence the
area this weekend keeping temperatures seasonable. The
probability of precipitation this weekend has fallen to single
digit percentages for most areas. Upper level ridging returns
Monday, bringing a return to warming temperatures and dry
conditions. Well above normal temperatures are expected by mid-
week.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...Stubborn clouds
have kept temperatures down across much of the region, a welcome
relief for many. By tonight into Saturday, an upper level low
spinning off the coast will draw nearer, bringing some
additional cloud coverage to the region, but providing
insufficient moisture to produce much in the way of
precipitation. This will keep temperatures near seasonable
levels through the weekend, but will also make nailing specific
temperature forecast challenging since they will be somewhat
sun-dependent. Chances for any precipitation have dwindled to
less than 10% across the board and the chances for thunderstorms
are even lower.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...As we move into next week,
the upper level low remains just offshore but a west coast ridge
is expected to amplify significantly Tuesday and Wednesday. By
Wednesday, this is expected to result in temperatures rising
back up into the 80s to low 90s across the region, persisting
through at least Thursday. This will result in another period of
heat with widespread HeatRisk values in the Moderate (orange)
category and isolated Major (Red) HeatRisk in favored areas.
This will also bring another period of fire weather concerns
given the dry conditions. See the FIRE WEATHER section for more
details. There is an overall signal for decreasing temperatures
by Friday. However, there is a decent signal for temperatures
to remain above normal beyond the day 7 time frame.
-Wolcott-

&&

.AVIATION...Southerly flow aloft as an upper level low remains
well offshore. Mid to high level clouds continue to remain over
western Washington, with mostly all terminals having VFR
conditions this afternoon. The exception being KHQM, where marine
stratus continue to linger over the terminal for MVFR/IFR
conditions. These lowered conditions will likely stay throughout
the remainder of the evening as stratus will fill in again
overnight into Saturday morning. Expect the same MVFR/IFR
conditions throughout most interior terminals (KOLM, KPWT, KCLM),
before slowly dissipating by 19z-20z. Stratus may filter into
Central Puget Sound but confidence is low. Winds remain light
southerly/southwesterly.

KSEA...VFR conditions this afternoon as lingering low clouds have
dissipated. S/SW winds 5 to 10 knots becoming light overnight. VFR
will likely continue Saturday morning but there is a 25-30% chance
of MVFR/IFR stratus filtering into the terminal by 15z and
continuing until early afternoon where VFR will resume.

Mazurkiewicz

&&

.MARINE...Varying degrees of onshore flow will continue throughout
the waters into this weekend. Westerly pushes down the Strait of
Juan De Fuca can be expected each evening, with the strongest push
likely happening Saturday evening. Winds may reach Small Craft
Advisory criteria, but right now confidence is low. Surface high
pressure looks to develop over the coastal waters by midweek next
week.

Combined seas around 2 to 4 feet will continue throughout the
weekend and into the first half of next week. Seas will then build
to 4 to 6 feet by midweek.

Mazurkiewicz

&&

.FIRE WEATHER...Weak onshore flow into the weekend is expected to
keep temperatures in check with good to excellent nightly relative
humidity recoveries. An upper level low parked offshore over the
weekend could trigger isolated thunderstorm activity over the North
Cascades late Saturday, but probabilities remain quite low...capped
at around 10 percent. This offshore low will shift away from the
area early next week with strong upper ridging rebuilding across the
area. As a result, temperatures are expected to climb once again to
well above average. Afternoon relative humidities in the 25-35%
range are expected, with some higher terrain locations could get as
low as 15-25%. Wednesday and especially Thursday are the days of
most concern for hot, dry, and unstable conditions across the
majority of the area.  Fuel moisture levels are already low across
much of Western Washington and the upcoming very warm and dry
weather will further cure both live and dead fuels.
27

&&

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

&&

$$