178
FXUS66 KSEW 261525
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
825 AM PDT Sat Sep 26 2026

.SYNOPSIS...
Weather settling down today with upper level trough to the east,
surface high pressure over the area and split flow aloft
developing off the coast. Little change in the pattern tonight
and Sunday. Flow aloft consolidating off the coast Sunday night
but next system not reaching the area until Tuesday. Much
weaker system most likely will fall apart before it gets to
Western Washington Thursday. Upper level ridge building Friday
with thermally induced surface trough developing along the
Oregon coast.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
No major updates have been made this morning. See below for an
updated aviation section.

Dry weekend in store for Western Washington. Upper level trough
east of the area early this morning. Surface high pressure
building today. Split flow aloft developing off the coast today
as well. Little change in the pattern tonight and Sunday.
Patchy fog developing this morning will dissipate before late
morning. A little more fog coverage Sunday morning as the air
mass continues to calm down. Highs today and Sunday even with
some sunshine a little below normal, lower to mid 60s. Lows
tonight in the 40s and lower 50s.

Pattern changes beginning Sunday night with the flow aloft
becoming consolidated off the coast. Next system well to the
northwest, near Haida Gwaii. Mostly clear skies allowing
temperatures to drop into the upper 30s and 40s. The forecast
low of 46 at Seattle-Tacoma airport would be the coldest low
since 45 degrees on May 30th.

Increasing middle and high level clouds Monday as the next
weather system continues to move southeast down the British
Columbia coast. Chance of rain along the north coast by late in
the afternoon. Highs again in the lower to mid 60s. Felton

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Models in good agreement with rain out ahead of the system over
the northern portion of the area Monday night. Slow moving front
dragging through Western Washington Tuesday into Tuesday night.
Not much cool air behind the front with minimal post frontal
shower activity Wednesday.

Inconsistency in the solutions increasing Wednesday night
through Thursday night. Operational runs are dry but enough
ensemble solutions indicating light precipitation to keep
slight chance pops in the forecast. Confidence in this scenario
not very high. Will not be surprised if the pops fall out of the
forecast in the next few runs.

ECMWF has strong upper level ridge building Friday with
thermally induced surface trough developing along the Oregon
coast. GFS has this scenario as well but is 24 hours behind the
ECMWF. For now the general idea is dry and warmer heading into
next weekend. Felton

&&

.AVIATION...
Northwesterly flow aloft this morning and this
afternoon as an upper level ridge builds over the coastal
waters. This will turn more zonal this evening as split flow
develops between this low and a developing trough off the OR
waters. Surface winds south to southwesterly this morning before
turning more north to northeasterly this afternoon. Speeds
generally 4-8 kts this morning before increasing to 8-12 kts
this afternoon. Wind speeds expected to ease tonight back into
that initial 4-8 kts range.

Most locations still seeing VFR conditions this early morning
although some isolated MVFR to IFR conditions are present. As winds
continue to ease this morning, cigs expected to lower due to
abundant low-level moisture with widespread MVFR/IFR conditions
expected by 12Z this morning. Cigs expected to lift and return to
VFR in the usual 18-20Z time frame and persist for the remainder of
the TAF period.

KSEA...VFR conditions in place with FEW-SCT clouds around 2000 ft.
VFR still expected around 18Z with skies clearing throughout
the day thanks to building upper level ridge. Southerly surface
winds turning northerly after 18Z with speeds increasing to 8-12
kts.

33/18

&&

.MARINE...
Weak high pressure and winds turning light offshore
today. On Sunday, an approaching frontal system will dissipate
over the offshore waters. A stronger frontal system will reach
WA Monday night and Tuesday with increasing south winds.
Additional headlines may be needed for this time frame should
forecast remain consistent.

Seas generally 5-7 feet and will continue to ease this morning until
reaching 3-5 ft by noon today. Wave heights rebound this evening
slightly this evening to 4-6 ft before reaching 7-9 ft Sunday and
into Monday. With frontal passage expected Tuesday, seas may rise to
9-11 ft and may need headlines.

33/18

&&

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

&&

$$