382
FXUS66 KSEW 150330
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
830 PM PDT Wed Aug 14 2024

.SYNOPSIS...Afternoon sunshine and near normal temperatures
through Friday. The pattern looks to trend wetter into the
weekend with what amounts regarding good chance of widespread
precipitation for much of the region, with a threat of
thunderstorms for the lowlands.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...Forecast remains on track
this evening with weak high pressure over the region. No updates
required tonight with the previous sections following below.

The aforementioned high pressure will get replaced by weak
troughing over the Pacific Northwest starting on Thursday, with
more cloud cover, cooler temps, and mountain showers. Along with
mountain showers, there is a chance of thunderstorms primarily in
the North Cascades Thursday afternoon and evening. High temps
will generally be in the mid 70s.

An upper level low centered in Canada will gradually drop down and
center just offshore our area on Friday, with a continued chance
of showers and thunderstorms primarily in the North Cascades. This
upper level low will continue to spin offshore on Saturday,
placing western Washington in a moist S/SW flow.

Latest guidance suggests widespread shower coverage for most of
the area on Saturday. Along with increased precipitation chances
that we have not seen in a while, there is a threat of
thunderstorms for most of the lowlands and Cascades. Probabilistic
guidance suggests around a 15-25% of thunderstorms late Saturday
afternoon into the evening hours, increasing to around 30% through
the overnight hours into early Sunday morning. There is
definitely some ensemble uncertainty regarding the position of
the upper level low offshore, which could lead to differences in
rain amounts, timings, and thunderstorm chances. As for now, we
will continue to monitor the threat as new guidance becomes
available.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Ensemble guidance
continues to highlight S/SW flow for a chance of showers and
thunderstorms through Sunday. Conditions look to trend drier
heading into Tuesday, with ensembles struggling on precipitation
chances later on in the week.

Mazurkiewicz

&&

.AVIATION...Light southeast flow expected tonight into Thursday with
weak high pressure over the area. BKN mid level clouds continue
across portions of Puget Sound this afternoon, with VFR for most
areas. Stratus will further develop along the coast into this
evening and spread inland into Puget Sound Thursday morning.
Generally MVFR/IFR with stratus in Puget Sound during this period
with LIFR cigs along the coast. Cigs will improve to VFR Thursday
afternoon. Lower vsbys possible tonight along the coast. W/NW winds
will become lighter tonight.

KSEA...VFR mid level cigs this afternoon. VFR will continue into
early tonight. MVFR stratus expected Thursday morning, generally 12-
18z. There is approximately a 15% chance of IFR cigs during this
period. Cigs will improve to VFR Thursday afternoon. W/NW winds into
this evening at 5 to 8 kts will become light NE tonight and
transition S/SW Thursday morning. JD

&&

.MARINE...Onshore flow pattern continues through this week across
the area waters with diurnally driven westerly pushes through the
Strait of Juan de Fuca. Brief SCA wind gusts may occur this evening
into early tonight for portions of the central and eastern Strait of
Juan de Fuca, but they are not expected to be widespread. Confidence
is a bit higher in SCA winds through the Strait of Juan de Fuca
Thursday evening into Thursday night with increasing west winds.
Otherwise, northwest winds continue over the Coastal Waters through
Saturday. Areas of lower visibilities due to fog is possible tonight
for the inner Coastal Waters. In addition, there is a threat for
thunderstorms, especially for the inner waters Saturday afternoon
through Sunday morning.

Seas will generally remain 3 to 5 feet through Saturday. JD

&&

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

$$