438
FXUS66 KSEW 021605
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
905 AM PDT Thu Oct 2 2025

.SYNOPSIS...An upper level low will sink southward today, wrapping
moisture into western Washington as it does so. This will keep the
chance for showers over the area. Dry conditions expected to emerge
tonight. Although generally dry conditions are expected for the
remainder of the forecast due to high pressure aloft, some weak
disturbances may allow for a chance for showers this weekend.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...The upper level low continues
to churn out over the Pacific, bringing in another wave of showers
to the area as per current radar. Most activity is focused on the
Olympic Peninsula and moving north-northeastward, so difficult to
say how much of an impact this might have on locations east of the
Sound, including the Seattle metro area. Ever since the sun went
down last night, no lightning has been detected with this precip and
as such will likely rely on daytime heating to introduce the energy
necessary for convection. That said, models do show some
instability, but it is primarily focused on the coastal waters and
the immediate coastal area. Given the strongest activity seemed to
be focused there yesterday, seems like a good fit for isolated
thunderstorms to be a prospect there this afternoon and early
evening.

The upper low wastes no time plunging to the south by this evening,
taking the majority of its associated moisture with it. This should
result in dry conditions over W WA as early as this evening,
although most likely overnight tonight. Models remain on track for a
strong upper level ridge to build over the Pacific, becoming the
main influence to W WA weather for the remainder of the short term.
As the ridge strengthens, temperatures will remain mild and
seasonable...however there is some consistency in advertising a
couple of weak disturbances on the leading edge of this ridge. This
could result in slight chance to chance PoPs over the area at times
Friday evening into Saturday, but probabilities remain low enough to
add some confidence to a generally dry close to the short term.

18

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...The upper level ridge
remains the main weather feature for the long term portion of the
forecast as its axis gradually shifts eastward throughout the
period. This looks to ensure dry conditions for the first half of
next week. This feature will initiate a warming trend, bringing a
return to daytime highs in the lower 70s in the interior lowlands
Monday and Tuesday. Some ensemble members hinting at an upper level
trough sinking down toward the area late Tuesday into Wednesday,
pushing the ridge axis back westward and out to sea. While this
could reintroduce rain to the forecast, given how far out this would
occur along with this being a relatively new-ish solution, not much
confidence at this time. As such, the low PoPs provided by the NBM
is in line with current thinking until this solution becomes either
more consistent, includes more members or both.

18

&&

.AVIATION...Southwest flow aloft will continue through today before
becoming light tonight as an upper low weakens and moves across
Western Washington. VFR conditions for the majority of terminals
this morning with areas of MVFR/IFR cigs along the coast with
continued showers. VFR conditions are expected this afternoon with
rain showers lingering, mainly along the Olympic Peninsula. Low
stratus may develop later tonight into Friday morning, along with
potential for fog development, especially in prone areas due to
residual moisture and light winds. South winds through this
afternoon will become light tonight.

KSEA...VFR conditions into tonight with mid and high clouds. A few
rain showers may be around Puget Sound this afternoon, but
predominantly dry conditions are expected at the terminal. Low
stratus or fog development may occur Friday morning, but confidence
remains low in location at this time. Current probabilities for
IFR/LIFR cigs are 25% and 20% respectively between 13 and 18z
Friday. Otherwise, S/SW surface winds may become VRB for a brief
period this evening (mainly between 02-06z). JD

&&

.MARINE...Gale force southerly winds will start to decrease in
strength later this morning as a weather system starts to weaken
offshore. Winds will lower to small craft strength, therefore
have continued the Small Craft Advisories for the Coastal Waters,
Eastern Entrance of the Strait, and the Northern Interior Waters
until this afternoon. Winds will continue to become light heading
into Friday, along with winds taking a more northerly direction
into the weekend.

There remains a 15-20% chance of thunderstorms over the Coastal
Waters this afternoon. Convective showers or thunderstorms may be
accompanied by brief erratic winds and small hail. The
thunderstorm threat over the Coastal Waters will diminish by the
evening hours.

Combined seas this morning of 15 to 18 feet. Seas will subside
later this morning 13 to 15 feet, and further lowering below 10
feet by this evening. Seas will lower to 4 to 6 feet by Friday
morning and maintain that height over the weekend.

Mazurkiewicz

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From James Island To Point Grenville
     Out 10 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville
     To Cape Shoalwater Out 10 Nm-Grays Harbor Bar.

     Small Craft Advisory until 2 PM PDT this afternoon for East
     Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland
     Waters Including The San Juan Islands.

&&

$$