875
FXUS66 KSEW 061533
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
833 AM PDT Sun Oct 6 2024

.UPDATE...Fog is set in place across the Chehalis and Snoqualmie
river valleys, as well as extending into portions of northern
King County. Elsewhere, broken mid-level clouds continue to
prevail across the northern half of the region. Temperatures as
of 830 AM range from the upper 30s to mid 40s. Once clouds break
away within the next few hours, temperatures should be able to
rise into the mid to upper 60s, even to near 70 through the
Southwest Interior. See below for the remainder of the forecast
discussion, as well as an updated aviation section. LH

&&

.SYNOPSIS...The warmest temperatures of the forecast period are
expected on Monday as an upper level ridge becomes positioned over
the northwest. The ridge will transit east on Monday evening, for
a trough and front to arrive and keep rain showers in the forecast
through mid week.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...As the ridge establishes
itself in the region today and into Monday, expect slightly above
average temperatures. Today will be in the mid to upper 60s, with
temperatures likely peaking for the week on Monday in the low to
mid 70s. Areas of fog are likely this morning, with the most
recent satellite imagery as of 09Z showing pockets of it starting
to develop in the Southwest interior and will likely settle in
river valleys.

The ridge will shift more east later on Monday, giving the system
impacting British Columbia a chance to sink south and weaken as
it sags into western Washington. Rain chances increase during the
afternoon and evening hours on Monday, and while QPF amounts have
increased slightly from the previous forecast, only a quarter to
half inch of rain is expected along the Olympics and areas of the
north Cascades. The metropolitan areas of Puget Sound are likely
to see around a tenth of an inch of rain.

The broad trough pattern offshore lingers into Tuesday, keeping
chances for rain in the forecast, with minimal amounts expected
into the middle of the week.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...The core of the offshore
trough nears closer to the coast by Wednesday, dynamically
renewing the chances for showers, but the majority of the region
should only see a few hundredths of an inch rain through Thursday.
Ridging cuts off the chances for precipitation late in the week,
which will bring up the temperatures again, which is still in line
with the Climate Prediction Center outlooks for the next 6 to 10
days that favor above average temperatures and below average
precipitation. This is also in good agreement in the ensembles and
cluster analyses.

Kristell

&&

.AVIATION...Areas of MVFR/IFR fog and low stratus with localized
LIFR along the coast, Chehalis Valley, and surrounding the Puget
Sound this morning. Improving conditions by the late morning/early
afternoon with most terminals returning to VFR with passing high
clouds. Winds will remain out of the S/SW generally 7 kt or less
today. Another marine push early Monday morning will likely bring in
another round of MVFR to IFR low stratus and patchy fog.

KSEA...LIFR in shallow fog. Conditions should improve as the sun
continues to rise, with fog favored to scatter out by 17-18z.
Conditions will return to VFR with light SW winds throughout the
day. Another morning of MVFR to IFR fog is likely early Monday
morning, but impacts remain uncertain.

15

&&

.MARINE...Surface high pressure over the coastal waters will
continue today shifting closer to the coast. This will allow for
southerlies to develop over the coastal waters and south to
southwesterly winds over the interior waters by this afternoon. A
dissipating cold front will bring borderline SCA level winds to the
coastal waters on Monday, however latest model solutions putting
most speeds just under advisory criteria and as such, will not put
forth any headlines with the morning forecast issuance. Another weak
system is on track to follow mid-week.

Seas 3 to 5 ft will gradually rise throughout the day, peaking at 7
to 9 ft by the start of Monday before subsiding slightly to 6 to 8
ft Monday evening, where they will remain into mid-week.

18

&&

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

$$