Mount Walker, Washington Weather Forecast Discussion

609
FXUS66 KSEW 212248
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
348 PM PDT Sun Sep 21 2025
.SYNOPSIS...Cooler weather with a few lingering showers Sunday
evening will will trend drier and warmer Monday. Warmest days look
to be Tuesday and Wednesday, with typical late September weather
with near normal temperatures and potential for precipitation Friday
into the weekend.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Partly cloudy
skies with some sunshine this afternoon behind this mornings frontal
system and generally dry conditions. Satellite and radar imagery
showing a few showers beginning to develop along the northeastern
portion of Jefferson County, perhaps hinting at the convergence zone
that the HREF and other hires ensembles have been forecasting for
the afternoon and evening hours. The isn`t much instability this
afternoon, ensembles continue to show a 10% chance of lightning -
mainly associated with showers expected to develop with the weak
convergence zone.
Marine stratus will likely develop along the coast and some areas
through the Chehalis Gap into the South Puget sound into early
Monday morning with, light winds and fairly high dewpoints, areas
of fog should also be expected Monday morning.
Further drying Monday as upper level ridging builds into the region -
 helping temperatures will begin to warm as well, with  highs Monday
near 70, and into the 70s to low 80s south of Olympia and the
Cascade valleys Tuesday. Lows remain in the mid 40s to mid 50s.
.LONG TERM /THURSDAY THROUGH SUNDAY/...Upper level ridging will
keep Wednesday dry and similarly warm with highs again well into the
70s to low 80s for some locations. The grand ensembles continues to
highlight a consistent shift in the large scale pattern over the
Pacific setting the stage for more zonal flow into the Pacific
Northwest through British Columbia. Confidence continues to be good
in typical late September weather with near normal temperatures and
periods of rain and/or showers Friday into the weekend.
&&
.AVIATION...VFR for all terminals this afternoon and will prevail
for the rest of today. Low stratus will reform along the coast
overnight and push inland. Guidance suggests the push will be weak
and its northeastward extend may be limited to BFI. Calm winds and
lingering moisture from the recent rain may lead to patchy fog
developing overnight, with medium confidence (40%-60%) along the
coast and southwest interior (OLM). It is possible to see some
pockets of fog in the Seattle Metro vicinity but confidence is low
on whether the terminals will be impacted at this time. Improvement
into VFR is expected after 17z-18z for interior terminals and 20z
for the coast, prevailing for the remainder of the TAF period. Gusty
westerly winds through the Strait of Juan de Fuca will subside this
evening. Calm to light variable winds overnight.
KSEA...VFR at the terminal this afternoon and will prevail
throughout the day. Low stratus may move into the terminal
overnight. There is some uncertainty regarding the eastward extent
of the stratus, but guidance suggests a 30%-50% chance of MVFR
ceilings at the terminal. In addition to low stratus, patchy fog may
form near the vicinity of the terminal, however confidence is low
whether the terminal will be impacted.  If conditions do
deteriorate, improvement into VFR expected after 18z.
NE surface winds this afternoon/evening at 5-7 kt, shifting SE
overnight at 3-5 kt. Winds will become NW after 18z and then N/NE
Monday evening.
29
&&
.MARINE...A Small Craft Advisory remains in effect for the
central and eastern portions of the Strait of Juan de Fuca through
tonight for a strong push of westerlies.
High pressure will build over the waters today and Monday. Thermally
induced low pressure will expand northward along the coast on
Tuesday leading to weak offshore flow. Onshore flow returns midweek
as a dissipating front passes to the north of the waters. Generally
benign marine conditions throughout the week, with combined seas
below 10 ft through the forecast period.
29/27
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.
&&
$$

NWS SEW Office Area Forecast Discussion