315
FXUS66 KSEW 200939
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
239 AM PDT Wed Aug 20 2025

.SYNOPSIS...Cooler conditions will continue today with weak
troughing over the region. High pressure will build over the
Pacific Northwest late this week and remain situated across the
region through the weekend for warmer and drier conditions.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...An upper level low will shift
eastward through northern B.C./Alberta today with weak troughing
over western WA. Overall, the trough is dry with showers remaining
to our north. Temperatures will track slightly cooler than average
with highs in the lower to mid 70s (interior) and 60s along the
coast.

High pressure will build inland on Thursday for the start of a
warming trend. We`ll see an uptick in temperatures, especially
across the SW Interior, where highs in the 80s will return. We`ll
see further warming on Friday with widespread 80s expected across
the interior. Areas in the Cascade valleys will reach the 90s.
Moderate Heat Risk is expected across most lowland areas (away
from the sound). Fire weather danger is also elevated due to the
warming and drying with min humidities in the 20s and teens
(Cascades and south sound). 33

.LONG TERM /SATURDAY THROUGH TUESDAY/...Warm and dry conditions
will continue through the weekend and into early next week with
high pressure stalling over the West. Temperatures will peak on
Saturday with more 80s and 90s across western WA. Areas in the
Cowlitz valley are approaching the triple digits. Moderate Heat
Risk and elevated fire danger remain the big concerns. A weak
onshore push knocks temperatures down just a few degrees on
Sunday but we`re still warm and in the 80s to lower 90s. The
coast will be cooler and in the 60s and 70s. We don`t see a really
strong push Monday or Tuesday either, thus keeping interior temps
above average moving forward through the period. 33

&&

.FIRE WEATHER...An upper level ridge building over the area late
this week and into this weekend will bring warm and dry conditions
to western Washington. Periods of offshore flow will be possible
on Friday and Saturday, helping to dry out fuels from recent rains.
Elevated fire weather conditions are expected across portions of
the Cascades and for areas south of the Sound through the weekend
with high temperatures in the upper 80s to low 90s and minimum
RHs dipping into the 20-30 percent range during the day.

14

&&

.AVIATION...Westerly flow aloft is expected across Western
Washington today as an upper level ridge begins to rebuild across
the area. The low level flow is light onshore. Areas of MVFR stratus
this morning will dissipate by midday with VFR expected for the
afternoon and evening hours.

KSEA...Ceilings are gradually solidifying in the vicinity of the
terminal this morning. Expect a stratus deck around 020-030 to
hang around for a few hours this morning before scattering out to
VFR by around 18Z. Surface winds N/NE around 6 knots will become
N/NW 7 to 10 knots this afternoon.  27

&&

.MARINE...A surface ridge building into the coastal and offshore
waters today will remain in place into late this week, but will
weaken as thermally induced low pressure expands northward along the
coast Thursday into the beginning of the weekend. The thermal trough
will shift inland by Sunday. The gradient between the surface ridge
offshore and coastal thermal trough will lead to some breezy north
to northwest winds over portions of the coastal waters over the next
few afternoons and evenings, but winds should remain mostly below
small craft advisory thresholds. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT early this morning for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

&&

$$