Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
934
FXUS66 KSEW 130318
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
818 PM PDT Sat Sep 12 2026
.SYNOPSIS...
A low pressure system will traverse western Washington tonight
into Sunday, bringing rain and chances for isolated
thunderstorms this afternoon. Drier conditions return Monday
with temperatures gradually warming back up throughout the course of
the week.
&&
.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
Widespread rain continues to pivot across the region as
expected, with a few isolated thunderstorms developing near the
Olympics.
The main bulk of the rain will move across the area overnight
into Sunday morning. Areas north of the Strait of Juan de Fuca
will likely remain mostly dry. The areas expected to see the
most rainfall will be across the south Cascades where localized
amounts of up to 1.5-2.0" of rain will be possible. There is
around a 40-60% chance of seeing 2" of rain over the Cascades of
King County and southward. Even portions of the lowlands may see
significant rain, with a 40-80% chance of seeing 1" of rain
from Seattle southward and east of I-5.
Rain will slowly taper off from west to east, first along the
coast in the morning then through the lowlands by the
afternoon. Winds will also increase Sunday as the system
departs, but remain mostly benign with peak gusts in the 20-25
mph range.
High pressure will begin to build in the wake of the system on
Monday, with the supporting upper level trough well to the east
and northwesterly flow aloft.
Temperatures through Monday will remain below normal, with highs
in the mid to upper 60s and lows in upper 40s to mid 50s.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
A shortwave trough will move through the flow Monday night into
Tuesday, bringing a reinforcing push of clouds, through little
to no precipitation is expected with this system. Following this
system, the upper level ridge building over the northeast
Pacific will move over the Pacific Northwest through the end of
the week, bringing a drier, sunnier, and warmer pattern. A
surface thermal trough will develop, allowing winds to turn
lightly offshore. Highs look to rise by Thursday into the upper
70s to low 80s.
62
&&
.AVIATION...
An upper level low will shift inland tonight allowing showers and
isolated thunderstorms to persist this evening and retaining at
least some shower activity overnight and into Sunday. Most terminals
reporting VFR conditions however isolated MVFR to IFR conditions
will still be possible under showers. Widespread low-level moisture
will allow for cigs to decrease tonight with abundant MVFR to IFR
conditions expected overnight and into Sunday. While cigs will
gradually lift throughout the day, any significant breakout does not
seem to be in the cards at this time. Latest guidance suggests that
conditions may only improve to high-end MVFR at best while those
terminals more prone to lower cigs only seeing recovery into low-end
to mid MVFR. Southwesterly winds generally ranging 5-10 kts will
persist throughout the TAF period.
KSEA...Above discussion applies as general trends will apply to SEA.
Any potential thunder threat seems to be over at this point in the
evening and MVFR cigs still on tap for around 09Z tonight. While
cigs will lift during the day Sunday, terminal will remain within
MVFR conditions for the remainder of the TAF period once they set in
tonight. Current NW winds expected to shift SWerly tonight and
remain there. Winds may be slightly stronger than discussed above
generally ranging closer to 8-12 kts.
18
&&
.MARINE...
Surface low pressure will shift into OR tonight with highest
winds in western Washington through the Strait of Juan de Fuca -
a Small Craft Advisory remains in effect. Onshore flow will
increase on Sunday as the low moves farther inland. SCA winds
are possible over Puget Sound/Hood Canal and the Northern Inland
Waters (as well as the strait). Will allow next shift to
consider prospects once latest model data arrives. Onshore flow
will ease moving into Monday. The flow will turn offshore
Tuesday and Wednesday as a thermal trough forms along the coast.
Seas generally 4 to 6 feet although may lift to 5 to 8 ft in the
outer coastal waters Sunday afternoon and evening.
33/18
&&
.FIRE WEATHER...
Fire weather concerns remain minimal through the next week.
Showers and a chance for isolated thunderstorms this evening will
be followed by wetting rains across most of the southern half
of the region overnight into Sunday. The pattern turns drier and
warmer mid to late week, with the surface winds going light
onshore. Daytime minimum relative humidity look to drop below
30% which will allow more reactive fuels to start to dry out.
62
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 6 AM PDT Sunday for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
&&
$$
NWS SEW Office Area Forecast Discussion