300
FXUS66 KSEW 052232
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
332 PM PDT Sat Oct 5 2024

.SYNOPSIS...A warming trend will continue through Monday as a weak
upper level ridge moves through the area. Patchy fog will be
possible in the morning. An upper level trough and associated
surface cold front will drift southward from British Columbia
through the beginning of the week and weaken, bringing light rain
chances through most of the week.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...A thin blanket of
altostratus covers the northern half of the region as a warm front
moves onshore onto British Columbia. This system will remain up
to the north, keeping at least the southern half of the region
mostly clear, with mostly high clouds to the north. Light offshore
flow and a weak upper level ridge moving through this weekend
will allow temperatures to warm each day, with highs in the mid
60s to near 70 on Sunday, up to the low to mid 70s on Monday,
mainly for the interior and away from the water. Areas of fog will
be possible in the morning, especially Sunday morning, with lows
dropping into the low 40s. Fog will be most likely over the
Southwest Interior, and the Kitsap Peninsula, as well as in the
river valleys--in a similar manner to what occurred this morning.

As the ridge slowly shifts eastward through the beginning of the
week, that will allow the system presently over British Columbia
to shift southeastward towards our area, allowing for chances of
rain to begin as early as Monday afternoon over northwestern
Washington. This system will continue to slowly shift southward
early on Tuesday but weaken as it does so. Rainfall amounts will
be light, with most of the area seeing a few hundredths to a few
tenths of an inch possible. The best chance for more substantial
rainfall will be in the northwest Olympic Peninsula near Neah Bay,
where up to a half an inch is expected with locally higher amounts
up to an inch are possible around Cape Flattery. All in all, and
over the span of two days, this system currently does not look to
be hydrologically impactful.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Chances for light rain
look to continue into the end of the week as the trough continues
to dig southward and with a very slow westward progression with a
large ridge building over the central U.S. If the ridge builds
farther westward, that could keep the trough farther west and
bring a break to precipitation chances late week. Ensembles
finally kick the trough eastward on Friday with a fairly sharp
ridge quickly building in behind that for next weekend. If that
evolution occurs, that will allow for a warming trend and drier
weather, which concurs well with the Climate Prediction Center`s 6
to 10 and 8 to 14 day outlooks.

LH

&&

.AVIATION...VFR with light shower and virga activity grazing the
Olympic Peninsula and northern interior this afternoon and evening.
Areas of MVFR/IFR in low stratus and patchy fog are favored to
develop west of the Puget Sound once again early Sunday. Patchy fog
with MVFR to IFR conditions east of the Sound less favorable Sunday
morning (10% to 20% chance) and would burn off quickly after
sunrise. High pressure will continue to build into the region Sunday
afternoon, allowing for more VFR conditions with little more than
high clouds. Surface winds generally light out of the north 10 kt or
less this afternoon, becoming light overnight.

KSEA...VFR with BKN high clouds and N/NE winds 6-9 kt through the
evening. Models continue to show potential for patchy fog
development mid-morning Sunday which may cause short-lived MVFR/IFR
conditions. Winds will switch to SE/SW by Sunday morning and will
remain 7 kt or less.

15

&&

.MARINE...A surface ridge will continue to build into the
region into Sunday, with northerly winds today shifting to southerly
later on Sunday as a dissipating cold front approaches. The front
will cross area waters on Monday, bringing in a surge of winds and
higher seas. While criteria is borderline for a SCA, conditions will
continue to be monitored as the system gets closer. Another weak
system is on track to follow mid-week.

Seas at 4 to 5 ft will rise to 7 to 9 ft as a cold front crosses the
region late Sunday into Monday. Seas will stay between 6 and 8 ft
with a slightly stronger swell briefly bringing in seas up to 10 ft
later next week. Seas are on track to weaken to 5 to 6 ft by the end
of next week.

15

&&

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

$$