605
FXUS66 KSEW 291554
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
854 AM PDT Sun Jun 29 2025

.UPDATE...No changes to the overall forecast. Please see the
aviation and marine sections below for updates to those
forecasts.

&&

.SYNOPSIS...High pressure continues to build over the Pacific
Northwest, maintaining warm temperatures and abundant sunshine
across the region for the start of this week. Temperatures
remain well above normal Monday and Tuesday, but a return to
more typical temperatures is expected toward midweek as the next
disturbance pushes toward the region and brings a more zonal
flow pattern.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...High pressure continues
to build over the region, with a sunny and mild day in store
across Western Washington. Expect temperatures to generally
trend 5-10 degrees warmer today than yesterday across the area
with afternoon high temperatures topping out around 80. This
will be another day of Minor (Yellow) HeatRisk for most of the
region. Monday is shaping up to the warmest day of the stretch
for many, as the ridge axis remains overhead and the flow turns
lightly offshore. This will bring temperatures into the mid to
upper 80s with a few spots expected to reach the 90 degree mark.
This will result in a corridor of Moderate (Orange) HeatRisk
from northern King County southward through the Sound Sound and
across Hood Canal and the upper reaches of the Chehalis Valley.
Moderate HeatRisk is also expected in the foothills and Cascade
valleys. In addition to the heat concerns, expect that daytime
RH values will dip into the 25-35% range. Despite some recent
rain, some of the grasses other fine fuels likely will dry out
in this stretch and could elevate fire weather concerns early
this week.

Some onshore flow likely resumes into Tuesday for a cooldown for
areas west of Puget Sound, but the deeper onshore push may not
reach the interior until closer to Wednesday. Another warm day
in the Seattle to Tacoma urban corridor as well as in the
Cascades where the deeper marine air will be slower to arrive.
This will yield a second Moderate HeatRisk day for these areas
on Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...Closer to midweek
expect the flow aloft to become increasingly zonal, though it`s
worth noting that around 30% of global ensemble members would
favor an extended ridge-like pattern into Wednesday or even
Thursday. However, the forecast continues to favor the more
likely scenario of a deeper onshore flow bringing a return to
morning clouds and temperatures closer to seasonal normals
Wednesday and Thursday. While the forecast is mostly dry,
chances of a few showers do begin to increase for Thursday in a
nod to that cluster of solutions that open the door to the next
shortwave trough sliding through the region. Confidence remains
lower for the late stages of the week, including the
Independence Day holiday, with ensemble guidance still depicting
a wider range of potential outcomes. 12

&&

.AVIATION...An upper ridge axis will build into Western
Washington today with light west to northwest flow aloft. The low
level flow remains northerly. With the exception of some patchy
stratus near the immediate coast this morning, VFR conditions will
prevail areawide.

KSEA...Clear skies. Surface wind northeasterly less than 10 knots
this morning becoming northerly this afternoon and rising to 10 to
14 knots. 27

&&

.MARINE...High pressure will remain in place across the coastal and
offshore waters early this week. Thermally induced low pressure
expanding northward over the interior into Monday will lead to
increasing northwesterly winds over the coastal waters along with
choppy short period seas. Westerlies will increase in the central
and east strait later Monday and Tuesday as the thermal trough
shifts eastward with small craft advisory strength winds likely
Monday afternoon and evening and potential gales in the cards for
Tuesday. A dissipating front will approach the waters on Wednesday.

27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 5 AM PDT
     Monday for Coastal Waters From Cape Flattery To James
     Island 10 To 60 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.

&&

$$