005
FXUS66 KSEW 290410
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
910 PM PDT Thu Aug 28 2025

.UPDATE...Satellite imagery shows weak upper level feature over
Western Washington with the center between Seattle and Everett.
Thunderstorm activity mostly in Kittitas and Chelan county this
evening with only an isolated lightning strike in the Olympics
late this afternoon west of the Cascade crest. Middle level clouds
over the Southwest Interior this evening and near the Canadian
border. Low stratus right along the coastline. Mostly clear skies
over the remainder of the area.

Forecast on track tonight. Red Flag Warning expired at 9 pm.
Previous discussion follows with updated aviation and fire weather
section.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...A weak upper level low will
keep the chance of showers for Western Washington in the forecast
today. Scattered thunderstorms possible (20-40% chance) in the
Cascades this afternoon/evening. Latest radar imagery shows light
showers to the south over Lewis county and to the north over
Snohomish, Skagit, and Whatcom counties.. The upper low will
dissipate tonight and a weak upper level ridge will build over the
Pacific Northwest on Friday. The ridge will bring drier and
slightly warmer conditions to the region. The upper level ridge
will continue building on Saturday, but the ridge axis will move
into Eastern Washington as an upper level low slowly tracks
towards Washington. The upper level ridge to the east will
continue amplifying on Sunday, keeping the upper level low
stalled over the Pacific. As a result, this will bring
southwesterly flow aloft and the chance of PoPs (15-30%), with
the highest chances over the Cascades. In addition, there is a
small chance (10-15%) of thunderstorms over the Cascades.

.LONG TERM /MONDAY THROUGH THURSDAY/...Long range ensembles are in
good agreement that the upper level low will not move inland, as
an amplifying ridge will block its eastward trajectory. Rather
the upper level low will retreat to the north and give way for the
upper level ridge to rebuild over Western Washington on Tuesday
through late in the week. Dry and warmer conditions are favored
next week with the ridge in place. High temperatures will
gradually warm up throughout the week. By Thursday, high
temperatures will be in the in the 80s in the lowlands and 70s
along the coast.

29

&&

.AVIATION...Just middle level clouds associated with weak upper
level disturbance over the area this evening. IFR/MVFR stratus
right along the coastline. Light onshore flow overnight with
stratus moving inland but staying west of Puget Sound and the I-5
corridor over the Southwest Interior. Any marine stratus that
makes it way inland will retreat back to the coastline by 18z.
Middle level clouds thinning out by Friday morning as the upper
level disturbance dissipates.

KSEA...VFR conditions with some passing middle levels clouds
overnight. Could see scattered clouds around 500 feet 13z-16z.
Northwest wind 4 to 6 knots becoming southwest around 12z. Winds
trying to become northwesterly late Friday afternoon with the wind
direction ending up in the 250-280 degree range. Felton

&&

.MARINE...Generally light south to southwesterly surface winds
over the coastal waters will continue into Friday. Periodic
onshore flow will bring westerly pushes across the Strait of Juan
De Fuca each evening, with the strongest push being Saturday
evening, which may reach Small Craft Advisory criteria.

Combined seas around 2 to 4 feet look to continue through the
weekend and into the first half of next week.

Mazurkiewicz

&&

.FIRE WEATHER...Drier conditions are expected Friday as an upper
level disturbance dissipates over the area early in the day. 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 primarily the Cascades, but
probabilities and confidence in this occurring are low.

The upper level low offshore is expected to retrograde 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 with afternoon relative humidities dropping into
the 25-35% range in some areas. 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/Felton

&&


&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...None
PZ...None.

&&

$$