098
FXUS66 KSEW 031622
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
922 AM PDT Sun Aug 3 2025

.UPDATE...Latest satellite imagery shows the marine stratus is
well established across the majority of Western Washington this
morning. The stratus is expected to gradually scatter this
afternoon, with mostly mid to high clouds remaining. Otherwise no
significant updates to the forecast this morning. Refer to an
updated aviation section below. 29

&&

.SYNOPSIS...Cooler and dry conditions with increased cloud coverage
today into Monday as a shortwave moves across Western Washington.
Upper level troughing over the region Tuesday through Thursday, with
a frontal system bringing back precipitation chances. Conditions
will dry out and become warmer Friday into the weekend as an upper
level ridge builds over the region.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...Forecast remains consistent
with main weather feature continuing to be an upper level low off
the western coast of Canada and a generally troughy pattern in
place over the PacNW. A prominent shortwave will cross the area
throughout the day today and into early Monday, although this
feature is mostly dry with no precip chances and any clouds being
more born of marine pushes than anything else.

A secondary upper low takes the place of its predecessor late Monday
keeping the overall pattern aloft relatively unchanged, however this
follow-up feature carries with it a more convincing slug of moisture
and organized front. This feature will start to approach the
coastline Tuesday morning but makes very slow eastward progress
until the upper level low shifts more eastward Tuesday night into
Wednesday. This ultimately will keep any chances for rain in the
short term confined to the western half of the CWA.

Temps will remain mild today and again Monday with highs generally
in the upper 60s to lower 70s in the interior lowlands while coastal
adjacent spots will run a little cooler in the mid 60s. Locations
east of the Sound see a little more warming for Tuesday, with mid to
upper 70s possible while the approaching front keeps the Olympic
Peninsula and coastline relatively unaltered from the two preceding
days. Overnight lows in the lower to mid 50s will persist.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Main frontal passage is
expected on Wednesday and as such, that is when the best chances for
rain are expected throughout W WA. Model differences regarding the
track of the upper low as it moves south and eastward muddying the
picture with regards to how quickly post-frontal showers will exit
the area. Latest NBM manages to forge a good middle path, keeping
activity present Thursday morning and scattering it out as the day
progresses. Generally dry conditions return by Thursday evening and
into Friday. Deterministic GFS wants to keep the weather pattern
unsettled Friday and beyond with a deepening trough in the central US
drawing moisture into the PacNW, but it appears to be a sole
outlier, with majority of solutions establishing a fairly strong
ridge over the Western US for the remainder of the long-term period.

Daytime highs remain mild Wednesday and Thursday thanks to the
passing front...remaining in the upper 60s to lower 70s in the
interior, mid 60s near water. The impact of the building ridge is
swift with a warming trend kicking off. Highs Friday in the mid to
upper 70s in the interior, upper 60s near water and highs Saturday
getting into the lower 80s inland, lower 70s near water.

18

&&

.AVIATION...Weak upper level trough offshore moving inland
overnight will be east of the area by Monday afternoon.
Southwesterly flow aloft becoming light with the trough overhead
then westerly behind the trough.

In the lower levels deep marine layer over Western Washington this
morning. Top reports around 3500 feet over the interior. Stampede
Pass at 3700 feet in the Cascades reporting fog and low
visibility. Cross Cascades gradient near plus 7 mb and will only
go up with the cloud cover suppressing the daytime heating in
Western Washington. All this leads to a slow improvement in the
ceilings this morning. At 16z mostly MVFR ceilings with IFR
ceilings at the higher terminals. All locations MVFR by 20z and
VFR by 00z. MVFR ceilings redeveloping 09z-12z Monday

KSEA...IFR ceilings lifting to MVFR 20z and to VFR 23z. With deep
marine layer good chance will not scatter out but keep a broken
cloud deck around 4000 feet into the evening hours. MVFR ceilings
returning to the terminal around 09z. Southwest wind 4 to 8 knots.
Felton

&&

.MARINE...Onshore flow prevails through Monday with high pressure
off the coast and lower pressure inland. Highest wind and waves will
be found through the Strait of Juan de Fuca during the afternoon and
evening hours. A weak frontal system will cross the waters Tuesday
and Wednesday, followed by another weak system on Friday. A thermal
trough may form along the coast next weekend, with stronger NW winds
over the Coastal Waters. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Monday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$