Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
703
FXUS66 KSEW 271620
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
920 AM PDT Thu Aug 27 2026
.UPDATE...
An upper-low offshore is tracking inland and steering rain
showers into parts of western Washington this morning. Latest
KATX/KLGX scans show the activity primarily along the coast and
Olympics, spreading inland towards the Cascades later today. The
NBM has A 15-25% chance of thunderstorms for the North Cascades
this afternoon. High temperatures are forecast to top out in
the mid 60s to mid 70s with the coldest temps expected along the
coast. The previous discussion remains below along with an
updated aviation section:
&&
.SYNOPSIS...
Western Washington remaining in the upper level trough position
through Saturday. A pair of weak systems embedded in the trough
moving through today and tomorrow. Upper level low developing
in the trough moving over the northern portion of the area
Friday night into Saturday. Upper level low dissipating Saturday
night with the trough moving east. Temporary upper level ridge
Sunday. Dissipating front reaching the coast late Monday with a
weak warm front brushing the area Tuesday. A much stronger
front arriving Wednesday. This could be the strongest system to
impact the area since spring.
&&
.SHORT TERM /TODAY THROUGH SATURDAY/...
Satellite imagery shows upper level trough approaching Western
Washington with the trough axis just offshore this morning.
Middle level clouds out ahead of the trough over the area with
low stratus along the coast into the Lower Chehalis Valley.
Temperatures at 2 am/09z were in the mid 50s to mid 60s.
Upper level trough moving into Western Washington today with a
chance of showers west of Puget Sound and in the Northern and
Central Cascades. Slight chance of thunderstorms in the same
areas beginning late morning and continuing through the
afternoon. Some breaks in the cloud cover this afternoon. Highs
below normal, in the mid 60s to mid 70s.
Upper level trough remaining over Western Washington tonight
into Saturday. Weak disturbance embedded in the trough moving
through Friday morning for another chance of showers in the
northern portion of the area. Small upper level low developing
in the trough moving over Western Washington Friday night into
Saturday. Showers likely north and a chance of showers south
part by late Saturday morning. Small pool of cool air aloft
associated with the low destabilizing the air mass enough
creating a slight chance of thunderstorms from about Seattle
northward late Saturday morning into Saturday afternoon. Highs
Friday in the mid 60s to mid 70s, Saturday in the 60s and lower
70s. Lows in the 50s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Trough moving east Saturday night. Convergence zone over the
Central Puget Sound extending into the Cascades will keep a
chance of showers in the forecast. Temporary weak upper level
ridge moving through Sunday providing a dry, but not very warm,
day. Models in good agreement with a dissipating front reaching
the coast later Monday. Weak warm front brushing the area
Tuesday followed by the trailing cold front Wednesday. While
there is agreement on this general pattern the ECMWF is much
stronger with the cold front putting a 1000 mb surface low off
the coast. If the ECMWF verifies break out the Pumpkin Spice.
That has the look of a season ender. Not to say there will not
be any warm days in September if the ECMWF verifies. In the last
20 years there has only been one September in Seattle, 2016,
without at least one 80 degree plus day. Normal high
temperatures cool off quickly in September. By this time next
month the normal high in Seattle will only be 68 degrees. Felton
&&
.AVIATION...
South to southwesterly flow aloft as an upper level trough with
a weak front moves through the area today. This weak front will
bring in periods of MVFR ceilings for most terminals this morning,
along with some chance for some shower activity throughout the
afternoon. Terminals along the coast will likely see lower ceilings
for most of the day (KHQM). Mid level clouds will develop in the
afternoon, allowing for VFR to return to most area terminals by 18z
and continue through the evening. Shower activity will be sparse
across the area and be located largely in the Olympics, although
there is a 10-15% chance of thunderstorms in the afternoon mainly
over the North Cascades. However, confidence is fairly low, so will
not include it in TAFs at this time. S/SW winds this morning 5 to 10
knots, and will increase this afternoon with periodic gusts up to 20
kts across the interior.
KSEA...MVFR ceilings over the terminal expected to erode around 16z-
18z, with VFR returning by the afternoon. Winds will remain
southwesterly and will increase this afternoon, 8 to 12 knots, with
gusts up to 15 to 20 kts at times. Winds will start to decrease in
strength into the evening.
Mazurkiewicz/15
&&
.MARINE...
A weak frontal system will continue to move over the coastal
waters today. South to southwesterly winds will increase over
the area waters this afternoon, though winds are expected to
stay just below Small Craft Strength this afternoon. The
exception being Puget Sound and Hood Canal interior water zone,
as latest guidance suggests a (15-20%) chance of brief gusts up
to 21 kt this afternoon.
Weak systems will continue to move over the coastal waters
through the end of the week, which will continue onshore flow
and pushes down the Strait of Juan De Fuca. The push on Friday
may be leaning towards Small Craft Advisory at this time.
Otherwise, all other marine waters look benign.
Coastal seas remaining 4 to 6 feet through the weekend.
Mazurkiewicz
&&
.FIRE WEATHER...
For the most part low level onshore flow, cooler temperatures
and precipitation chances through most of the next week will
help ease fire weather concerns over the area. The only
worrisome feature is the slight chance ( 10-15 percent ) of
thunderstorms mainly in the North Cascades this afternoon and
again Saturday afternoon. If there is a thunderstorm it will
not be accompanied by much rain and it could produce erratic and
gusty outflow winds impacting existing fires. New lightning
strikes will pose a hazard and could lead to new fire starts.
Thunderstorm threat ending Saturday evening. Cooler weather
pattern continues into next week. Possible system next Wednesday
could bring wetting rains to the area. Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion