645
FXUS66 KSEW 050329
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
829 PM PDT Fri Oct 4 2024

.UPDATE...Lingering post-frontal showers continue this evening,
primarily over the Cascades. Showers will slowly taper off in
these areas later tonight. Patchy fog will develop into Saturday
morning, with areas of lower stratus across Western Washington. No
major updates this evening.

&&

.SYNOPSIS...Lingering showers continue this evening, especially in
the Cascades. High pressure builds this weekend bringing slightly
warmer temperatures. Rain chances return by the middle of next
week.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...The cold front has pushed
through Western Washington and is currently pushing eastward.
Much of the widespread precipitation has dissipated with the
frontal passage, but a few isolated showers can still be seen on
radar moving into Western Washington, especially a few cells near
the coast with the potential of a lightning strike or two. With
the cold front having pushed eastward, a Puget Sound Convergence
Zone is expected to develop over Snohomish County later this
afternoon bringing the a small chance of thunderstorms.
Precipitation chances will wane to 10-20% into the late evening,
with higher chances of 50-60% over the Cascades. Temperatures are
expected to rebound this weekend along the interior areas as a
surface high pressure settles over Washington this weekend. Expect
temperatures to reach the upper 60s to low 70s along these areas.
High pressure is expected to start moving eastward Monday morning
as a weak cold front begins to move eastward, opening the
opportunity for rain again during the afternoon for northwest
Washington. Accumulations should not be impactful as they will
remain under 0.25 in.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Some uncertainty exists
whether rain will persist throughout the rest of the week.
Ensemble guidance shows an upper level ridge redeveloping over the
Rockies. However, there is some uncertainty on the future
location of the ridge. There is general agreement through Tuesday
that the ridge axis will remain east of the area, leading to
southwest flow to dominate. The majority of ensemble solutions
favor the ridge to remain to the east allowing the opportunity for
rain to persist throughout the rest of the week. However, a small
group of members favor the ridge axis to build westward, keeping
the upper level trough offshore and hindering rain potential in
the area. If there is any precipitation that does make into the
area, no significant weather impacts are expected. Temperatures
expected to remain near normal throughout the week.

&&

.AVIATION...Northwest flow aloft overnight will become westerly
on Saturday as a low amplitude upper ridge axis shifts onshore over
Western Washington. Light surface winds, clearing skies and
lingering low level moisture will lead to the formation of areas of
IFR or localized LIFR in stratus/fog on Saturday morning. These
conditions will dissipate by 18Z with VFR under varying degrees of
mid/high level moisture Saturday afternoon.

KSEA...With skies clearing this evening and surface gradients
becoming flat overnight, confidence in the formation of some
stratus/fog has increased somewhat. Current thinking is to include
some tempo IFR conditions 12z-16Z and let overnight trends decide
whether to make that the predominant daybreak condition. Any fog
that does form should dissipate by 17Z-18Z with VFR for Saturday
afternoon under variable amounts of high clouds. Southwesterly
surface winds will continue to ease this evening and become
light/variable by dawn before veering light north/northwesterly
Saturday afternoon.    27

&&

.MARINE...A surface ridge will shift inland on Saturday turning the
flow northerly or weakly offshore Saturday night into Sunday. A
dissipating cold front will approach the coastal waters Sunday night
into Monday with an increase in southerlies for portions of the
coastal waters, but otherwise little to no impact. Another weak
system may follow Tuesday into Wednesday, but confidence in the
overall forecast picture by that time period is low. 27

&&

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

$$