Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
400
FXUS66 KSEW 022028 CCA
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
123 PM PDT Sun Aug 2 2026
.SYNOPSIS...
An upper level trough will move east of the area tonight. An
upper level ridge will build offshore tonight and Monday then
move inland Tuesday and Wednesday. The ridge will shift eastward
Thursday and Friday with increasing low level onshore flow at
the end of the week.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
Isolated showers continue to linger around the area early this
afternoon, but will diminish with skies clearing this evening
as an upper trough axis shifts east of the Cascades. An upper
ridge offshore will gradually build into the region Monday into
Tuesday. Thermally induced low pressure near the surface will
expand into the area Monday night and Tuesday. This will lead to
a pretty good jump in high temperatures areawide on
Tuesday...with upper 80s to lower 90s from Seattle metro
southward. This will begin to put a large portion of the
interior from Seattle southward into likely Moderate HeatRisk.
During this same period, north to northeasterly flow aloft,
especially around 600 millibars and below, will begin to import
regional wildfire smoke into the region. It will initially begin
aloft on Monday, but smoke models are showing near surface smoke
increasing by Tuesday. Moderate HeatRisk expands to most of the
lowland forecast area on Wednesday with temperatures slated to warm
a few degrees further as a 588-ish decameter ridge axis slides
overhead and the surface thermal trough remains oriented just inland
from the coast. However, with that said, the smoke factor is a
wildcard and may knock 2 to 4 degrees off of high temperatures -
models rarely handle this scenario well.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Low level onshore flow is expected to increase by later in the
day on Thursday as thermal low pressure makes the jump toward
the Cascades, but not before much of the interior sees another
very warm day with Moderate HeatRisk continuing away from the
immediate coast. Onshore flow increases further on Friday and
the flow aloft turns more zonal. This is expected to lead to
modest cooling, but temperatures, especially across interior
areas, are expected to remain a little above average. Ensembles
maintain the idea of some weak upper troughing arriving by next
weekend. But the negative height anomalies are small which, as
previous shifts have alluded to, simply point to a return to
"normal" temperatures for early August along with Minor
HeatRisk and dry conditions
27
&&
.AVIATION...
Westerly flow aloft will become north to northwesterly tonight
as an upper trough axis shifts east of the Cascades. The low
level flow will turn more northerly tonight into Monday.
Remaining shower activity will dissipate with VFR conditions
prevailing from mid-afternoon through the evening as skies
gradually clear out. A shallow IFR/LIFR stratus layer is
expected to form along the immediate coast early Monday morning,
but is not expected to impact interior terminals.
KSEA...VFR ceilings at or above 4000 feet are expected for much
of the afternoon before scattering out toward sunset. Surface
winds W/NW turning solidly N/NW and increasing to 10-13 knots
with a few higher gusts toward 00Z. Winds will ease to
northeasterly 4 to 7 knots overnight then rise to northerly 9
to 12 knots Monday afternoon.
27
&&
.MARINE...A strong surface ridge will remain centered well
offshore into midweek as thermally induced low pressure expands
northward across the interior of Western Washington. The
thermal trough will shift eastward toward the second half of the
week for increasing onshore flow. Winds will generally remain
under small craft advisory levels into Wednesday. However, the
presence of the thermal trough over Western Washington will
allow winds over the outer coastal waters to approach low end
advisory levels each afternoon/evening Monday and Tuesday.
Increasing onshore flow late in the week may necessitate
headlines for westerlies in the central/east strait.
27
&&
.FIRE WEATHER...
A strong warming trend will start on Monday and extend into at least
mid-week with Wednesday expected to be the hottest day of the
stretch. While this will result in low daytime RH values throughout
the CWA, the Cascades, the Cascade valleys, the adjacent lowlands of
the Chehalis river valley and the south Puget Sound area will be of
particular concern. Min RH values each of those days are expected to
slip into the teens. Wednesday will be of particular concern as Min
RH values could get as low as the low teens to upper single digits.
No significant winds or instability is expected during this time
frame, so Red Flag concerns are minimal. However, with RHs this low,
any wind will contribute to fire spread and as such, maximum caution
is emphasized at least into mid-week. Thursday sees some slight
cooling and thus a slight nudge upward in RHs, but not enough to end
concerns. Friday and beyond will see a much more significant rebound
to daytime RH values as onshore flow returns.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 4 PM this afternoon to 2 AM PDT
Monday for Central U.S. Waters Strait Of Juan De Fuca-
East Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 4 PM this afternoon to 3 AM PDT
Monday for Coastal Waters From Cape Flattery To James
Island 10 To 60 Nm-Coastal Waters From Cape Flattery To
James Island Out 10 Nm-Coastal Waters From James Island
To Point Grenville 10 To 60 Nm-Coastal Waters From James
Island To Point Grenville Out 10 Nm-Coastal Waters From
Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal
Waters From Point Grenville To Cape Shoalwater Out 10 Nm.
&&
$$
NWS SEW Office Area Forecast Discussion