Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
185
FXUS66 KSEW 030346
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
843 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/...
Latest radar imagery shows scattered showers from this afternoon
have largely fizzled out, although a stray shower over the Cascades
remains a possibility this evening. Switching to satellite, starting
to see some high level smoke already work into the area, mostly from
Canadian wildfires. This will remain aloft and as such have little
to no impact on air quality at this time and will mainly manifest as
some haziness. Inherited forecast remains on track with no evening
update needed. For additional forecast details, please refer to the
Previous Discussion section below. 18
From Previous Discussion...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...
Northwesterly flow aloft into the region tonight as an upper trough
continues eastward. Low level flow becomes northerly, brining some
elevated smoke from regional fires. A shallow IFR/LIFR stratus layer
is may from along the immediate coast early Monday morning, but is
not expected to impact interior terminals. Northerly surface winds
increase again during the day Monday.
KSEA...VFR conditions under generally cloud-free skies this evening.
Some elevated smoke from regional fires remains nearby during the
period. Otherwise, surface winds easing overnight, increasing again
tomorrow from the north at 9 to 12 kt by afternoon.
&&
.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 until 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 until 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