Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
529
FXUS66 KSEW 222107
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
207 PM PDT Mon Jun 22 2026
.SYNOPSIS...
Upper level ridge offshore moving over the area tonight into
Tuesday. The ridge will shift east Wednesday. Thermally induced
surface trough developing along the coast today moving inland
Tuesday night and east of the Cascades Wednesday morning. Very
warm temperatures over the interior the next three days. Much
cooler Thursday with low level onshore flow. First weather
system in two weeks moving through Friday. Upper level low
moving over Western Washington Saturday will move east Sunday.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Water vapor imagery shows upper level ridging along the coast
with a layer of high cirrus streaking across southern Washington.
Marine stratus will stay along the coast for the remainder of
the day due to offshore flow. The main story for the short term
will be on the warm temperatures.
Upper level ridging will move inland today and slowly exiting
the region by the end of tomorrow. A thermally induced surface
trough has started to form along the coast. This combination of
upper ridging and a thermal trough will raise temperatures up
to the 80s to low 90s today through Wednesday. Tuesday will be
the warmest day during this warm stretch. Expect Moderate
HeatRisk for most of the lowland areas with 25% chances for
Major HeatRisk for Seattle and Tacoma areas on Tuesday.
Therefore, a Heat Advisory is in effect most of the lowlands
locations except the coastal beaches through Tuesday night. The
Heat Advisory will end for all locations by Wednesday night as
the upper level ridge moves east. Temperatures will start to
moderate with the return of onshore flow by Wednesday night to
Thursday morning.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Ensemble models are consistently showing a weather system that
will start impacting the coastal areas by Thursday. This weather
system will bring cooler temperatures and chances for rain
showers. Chances for rain showers will expand on Friday for most
of western Washington. There is potential for the convergence
zone forming north of Seattle because of the onshore flow,
leading to Seattle seeing little to no rain fall on Friday. By
Saturday, the low pressure center will be over the state before
descending into the Great Basin. Temperatures will be cooler
with the onshore flow and the rain showers. Chances for
precipitation will linger in the Cascades on Saturday and a
little on Sunday.
By Sunday, ensembles show a minor ridging forming over the coast
with another weather system upstream. There is model
disagreement on the ridge placement due to the low pressure
center over Rocky Mountains. Current model run leans the
placement of the ridge near the coast, bringing a slight
warming trend and drier conditions for the coastal areas.
&&
.AVIATION...
VFR regionwide this afternoon as a few high clouds pass over the
terminals this afternoon and evening and cumulus clouds over the
Cascades. Winds this afternoon will be 10-15 kt with gusts up to
to 18-20 kts. Winds will shift to northeast at 5 kt or less
overnight. Marine stratus layer will stay along the coast and
infiltrating to the coastal terminals tonight. The probabilities
for MVFR ceilings are 25-40% and for IFR ceilings a 20-30%
chance tonight to early Tuesday morning. Otherwise, expect VFR
with high cirrus clouds elsewhere into tomorrow with winds
switching back to the north/northwest 5-10 kt in the afternoon.
KSEA...VFR expected through the TAF period. Winds this
afternoon will continue out of the northwest at 10-15 kt with gusts
to 18 kt. Overnight winds will switch to northeast at around 5
kt. Tuesday afternoon winds will return to northwest at 5-10
kts.
&&
.MARINE...
Offshore flow prevails across western WA with a
thermal trough along the coast. The thermal trough will shift
inland on Tuesday then east of the Cascades on Wednesday with a
push of westerly winds. Winds down the Strait of Juan de Fuca
will be strong with gales possible. Seas will also build to
10-11 ft over the outer Coastal Waters on Wednesday. The flow
remains onshore through the end of the week with highest
winds/waves in the strait and outer Coastal Waters. 33
&&
.FIRE WEATHER...
High pressure aloft combined with a thermally
induced surface trough over the area will create elevated fire
conditions through Tuesday. In addition to the warm, dry, and
conditionally unstable air mass, low level offshore flow will
drop minimum relative humidity values into the twenties, and
even the teens today and Tuesday afternoon. The upper level
ridge and thermally induced trough moving east Wednesday but
elevated fire weather concerns could linger. Fuels are
approaching critical levels, but the main concern remains dry
grasses or shrubs, or dead piles of fuels where brush fires may
be able to start (as seen the last few days). Onshore flow will
return with improved low level moisture Wednesday night and
Thursday. Weather system moving into the area will bring a
chance of wetting rains for the first time in a couple of weeks
Thursday night and Friday. Cool weather will continue through
the weekend.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 11 PM PDT Tuesday for Eastern Strait of
Juan de Fuca-Foothills and Valleys of Thurston and Lewis
Counties-Foothills and Valleys of the North Cascades-
Foothills of the Western and Southern Olympic Peninsula-
Island County-Lower Chehalis River Valley-Lowlands of
Lewis and Southern Thurston Counties-Lowlands of Western
Skagit and Northwestern Snohomish Counties-Lowlands of
Western Whatcom County-Middle Chehalis River Valley-
Northern Hood Canal-Olympia and Southern Puget Sound-Port
Townsend Area-San Juan County-Southern Hood Canal-Willapa
and Black Hills.
Heat Advisory until 11 PM PDT Wednesday for City of Seattle-
Downtown Everett / Marysville Area-Eastern Kitsap County-
Eastside-Foothills and Valleys of Central King County-
Foothills and Valleys of Pierce and Southern King
Counties-Foothills and Valleys of Snohomish and Northern
King Counties-Lowlands of Pierce and Southern King
Counties-Shoreline / Lynnwood / South Everett Area.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion