Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
975
FXUS66 KSEW 200956
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
256 AM PDT Mon Apr 20 2026
.SYNOPSIS...
Mostly warm and dry conditions will continue today ahead of a
pattern change through mid-week that will bring cooler
temperatures and increased chances for rain. Conditions are
favored to dry out and warm up by the end of the week and into
the weekend.
&&
.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Today will bring the last of unseasonably warm and dry
conditions over the next several days. As a deep upper level low
continues to meander southward along the Pacific coast, split
flow will develop aloft today for very similar conditions to
yesterday. Temperatures will peak in the low to mid 70s across
the inland lowlands, with highs in the 60s along the coast.
The cutoff low will begin to shift inland over Oregon later
tonight into Tuesday, advecting moisture northward into western
Washington. Higher terrain south of the Puget Sound and areas
along the Pacific coast may see light shower activity develop
as a result later today, with light accumulations possible.
After midnight, a stronger surge of moisture will lift
northward, bringing widespread showers across western Washington
through much of the day. Instability from the low to the south
may also produce a few lightning strikes over the western
Cascades Tuesday afternoon. Conditions will briefly dry out
Tuesday evening ahead of another round of widespread
precipitation as the low slowly progresses eastward towards the
Intermountain West. Snow levels will remain above 5000-6000 feet
as this system passes through, with minimal accumulating snow
over the higher peaks. Through Wednesday, the region will see
roughly a half an inch of rainfall or less, with the highest
amounts concentrated over the Cascades. Temperatures will also
cool considerably as this system passes over the Pacific
Northwest, with highs peaking in the mid 50s on Wednesday.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Light shower activity will taper off over the Cascades Wednesday
night, with conditions drying out and warming up heading into
the weekend. Models continue to show good agreement over a sharp
ridge of high pressure building offshore through Sunday,
bringing dry conditions and near normal temperatures through the
weekend. However, models continue to show disagreement over the
strength of the ridge and how long conditions will remain dry
before another pattern change.
15
&&
.AVIATION...
W WA still finds itself situation between an upper level ridge to
the east and an upper level low out over the Pacific centered off
the coasts of CA and OR. This will keep flow aloft mostly southerly
with occasional shifts to southeasterly from time to time. Surface
winds this early morning and into the late morning/early afternoon
will remain light and variable for some terminals, northerly 4-8 kts
for others. Terminals along the Sound will join in the northerly
winds by late morning. All terminals will see a shift to south to
southwesterly winds late this afternoon or early this evening with
speeds generally remaining in that 4-8 kt range. HQM, OLM and SEA
may see winds pick up this evening and early tonight, ranging 8-12
kts.
The aforementioned upper low will continue to churn moisture into
the area, but nothing in the way of precip is expected during the
TAF period...only high to mid clouds. As such, current VFR
conditions are expected to persist.
KSEA...VFR through the period. Northerly winds with occasional
shifting to the NE during the early morning then favoring NW late
morning and afternoon. Speeds generally 4-8 kts. Wind shifting to
the SW after 00Z and speeds increasing to 8-12 kts around 06Z.
Models have these winds easing early Tuesday morning.
18
&&
.MARINE...
Low pressure will spin offshore, off OR/CA, with light offshore
over western WA today. The low will shift inland and weaken
Tuesday resulting in increased onshore flow. Highest winds will
be through the Strait of Juan de Fuca, but should remain just
under SCA criteria. Onshore flow will continue through Thursday
with high pressure over the NE Pacific. Offshore flow may
develop toward the end of the week as a thermal trough forms
along the coast.
18/33
&&
.HYDROLOGY...
No river flooding is expected over the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion