766
FXUS66 KSEW 010334
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
834 PM PDT Wed Sep 30 2026

.SYNOPSIS...
High pressure will rebuild over the region in wake of a front
that moved through western Washington yesterday. A few areas of
fog will be likely next couple mornings as conditions dry out
from recent rains. A weaker front will bring a slight chance of
showers to the far north interior and Olympic coast Thursday
and Friday. This upcoming weekend and early next week remain
dry, as the ridge axis shifts through with warmer temperatures.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
The pattern overhead remains fairly zonal with the jet stream
over southern Canada. A broad ridge will continue to pass
overhead tonight, with high pressure down at the surface
centered over southeast British Columbia. Mid and high level
clouds will continue to fill in tonight into Thursday morning
ahead of a weak warm front that will pass through next couple of
days. The cloud coverage will likely limit the fog development
to the valley areas next couple of mornings, with overnight
temperatures ranging from the low to upper 40s. There is a
30-40% chance of showers in the north interior and northwest
Olympic coast Thursday and early Friday. Remaining areas will
stay dry. Temperatures will slowly warm up Thursday and Friday,
with highs approaching 70 in the Puget Sound/south interior, and
lows increasing into the upper 40s/low 50s.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Ensemble guidance remains locked on an amplifying upper level
ridge passing over the region over the weekend. This will likely
result in surface high pressure continuing to build over the
weekend with an offshore pattern, and temperatures warming up
into the mid 70s (approaching 80 in a couple valley areas in the
Cascades). With low temperatures around 50 during the weekend,
the HeatRisk will remain yellow (minor) with this pattern. As
the ridge moves east of the region early next week, temperatures
will decrease back into the mid 60s with lows remaining around
50. Conditions will remain dry through the long term forecast
period.

HPR

&&

.AVIATION...
Widespread VFR conditions with some high level clouds spreading
into the area from the west-northwest. VFR conditions are
expected overnight, with a similar - albeit less widespread
scenario of MVFR to IFR conditions with fog and areas of low
stratus Thursday morning. High resolution ensemble guidance
(LAMP) indicating the best odds in the most sheltered locations
particularly south of Puget Sound (KOLM). Northwesterly winds
7-9 kts will east late evening becoming northeast at many
locations.

KSEA...VFR conditions will persist overnight with some scattered to
broken ceilings above 15 kft moving into the area overnight.
Uncalibrated probabilities from LAMP for MVFR or lower conditions
remains around 3% Thursday morning. Northwest winds 8 or 9 kts will
east and veer to the northeast at 5 kts or less overnight.

&&

.MARINE...
High pressure will rebuild over the waters through the end of
the week, with a weak front moving through Thursday and Friday.
A thermal trough will build along the coast this weekend with a
brief period of offshore flow over the waters. Once the ridge
shifts eastward early next week, onshore flow return. The only
potential for hazardous winds (with gusts greater than 20 kt) is
the Strait of Juan de Fuca on Monday into Tuesday with the
initial push of onshore flow. This remains a 50-60% likelihood
this far out.

Seas will remain at 3-6 ft through the forecast period.

HPR

&&

.FIRE WEATHER...
Conditions will remain mostly dry going through the end of the
week into next week (except for a slight chance of showers in
the north interior/Cascades and northwest Olympics). An upper
level ridge and thermal trough pattern will build going into the
weekend across the region. This will turn the flow pattern to
light offshore. While critical fire weather conditions are not
expected, a few Cascade Valley areas may see relative humidity
values dip to as low as 30% as temperatures warm into the upper
70s to near 80 this weekend. Onshore flow will return early next
week as the ridge shifts eastward.

HPR

&&

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

&&

$$