568
FXUS66 KSEW 111006
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
306 AM PDT Fri Jul 11 2025

.SYNOPSIS...High pressure building offshore will result in an
extended period of warm and dry conditions across western
Washington that will persist well into next week. Temperatures are
expected to peak on Tuesday and Wednesday, potentially reaching
the low to mid 90s for many lowland areas.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...A high pressure ridge
building offshore will amplify towards the Pacific Northwest
through the short term, bringing warmer temperatures alongside dry
conditions. Onshore flow has weakened this morning, though areas
along the Pacific coast will see another day of cloudy skies from
marine stratus with mostly clear conditions elsewhere. The
incoming warmer air mass will bring high temperatures back into
the low to mid 80s across much of the lowlands, with the marine
layer limiting temperatures along the coast to the upper 60s to
low 70s.

Conditions Saturday and Sunday will bring more of the same as
zonal flow develops aloft, with marine stratus along the coast
and mostly clear conditions further inland each day. Conditions
will be dry region-wide with high temperatures peaking in the low
to mid 80s on Saturday, and a few degrees higher on Sunday as high
pressure starts to amplify. By Sunday, a majority of the interior
lowlands will see Moderate (orange) HeatRisk.

.LONG TERM /MONDAY THROUGH THURSDAY/...While a warming and drying
trend will continue into next week, forecast models have come in
to better agreement over a positively tilted trough passing
southward over the Pacific Northwest. This will do little more
than lower temperatures a few degrees across western Washington
alongside cloudy skies, with the potential for a few isolated
showers along the Canada border Monday afternoon.

Ensembles continue to show high pressure rebounding on Tuesday and
Wednesday, allowing for further warming across western Washington.
However, models have trended temperatures a degree or two cooler
as a cutoff low is now favored to meander southward across British
Columbia, impacting the strength of the high pressure ridge
offshore. Ensembles continue to show a high (60% to 80%) chance
of temperatures reaching 90 degrees or higher on Tuesday and Wednesday
across the lowlands south and east of the Puget Sound, with
temperatures peaking area-wide on Wednesday. Elevated overnight
temperatures in the upper 50s to low 60s will also provide little
relief to the heat during the day. This will result in widespread
Moderate (orange) HeatRisk across western Washington.

While cooling is on track for the end of next week, forecast
models show disagreements over the progression of the low pressure
system moving south over British Columbia. The degree of cooling
is uncertain for now, with an ensemble mean showing temperatures
staying in the mid 80s on Thursday with further cooling into next
Friday.

15

&&

.AVIATION...A brief transient ridge will pass overhead today (with
flow being northwest aloft). VFR conditions continue early this
morning in the interior terminals. Low fog & stratus just off the
the coast is not expected to go east of the Olympics this morning
(but it will drop areas along the coast down to LIFR through at
least this morning). Additionally, a push down the Strait of Juan de
Fuca may make it into KPAE (visibilities down to 1/2 SM at KNOW
confirm that it`s working its way down the strait, though may hold
just west of KPAE with less than a 20% chance of MVFR and lower).
Remaining areas not affected by stratus/fog will remain VFR today
(though a stronger push Saturday morning will bring at least MVFR
stratus into Puget Sound areas). Coastal fog/stratus will retract
back to over waters this afternoon before advancing back over
coastal terminals. Winds will remain northwest between 5-10 kt
(lighter overnight). Gusty winds are expected in the Strait of Juan
de Fuca areas this afternoon/tonight up to 25 kt.

KSEA...VFR continues this morning - chance of MVFR getting in
remains at 20% between 12-16Z but the expectation is that the
stratus will remain west of the terminal today. Skies will be clear
today, 50% chance MVFR stratus makes it back into the terminal
Saturday morning (10% chance of IFR). North winds at 5-10 kt.

HPR

&&

.MARINE...High pressure has begun to build back offshore. Flow
remains northwesterly offshore over the seas. Satellite/observations
along the coast confirm fog has developed with visibilities dipping
to below a mile at times - have issued a dense fog advisory for the
inner coastal waters/Grays Harbor/West Strait of Juan de Fuca
through 18Z (11 AM PDT). The fog may push down the remaining Strait
of Juan de Fuca waters, and may need to expand the advisory to the
central/east strait if observations on the coasts show lower
visibilities.

A push through the Strait of Juan de Fuca this afternoon tonight is
expected to bring higher end 20-30 kt winds (for a small craft
advisory), with low potential for a gale gust to 35 kt. Expect the
pushes to continue throughout the weekend into next week.

The coastal waters will see light winds today into Saturday (may get
a touch breezy this afternoon from Grays Harbor to Cape Elizabeth
but believe winds will largely remain below small craft advisory
criteria, though a brief gust exceeding 20 kt is possible). Winds
will pick up late this weekend into next week (exceeding 20 kt in
the outer coastal waters). Seas will also increase from 3-5 feet
today to 5 to 7 feet this weekend, continuing up to 6 to 10 feet
Monday into the work week (with steep sees due to shorter periods).

HPR

&&

.FIRE WEATHER...Mostly clear skies early this morning as high
pressure begins to build over the region, signaling the beginning
of a prolonged warming and drying trend starting today and
continuing through the middle of next week. Today will be notably
dry, with RH values dropping back into the 25% to 35% range over
the mountains as well as the interior lowlands south of the Puget
Sound. More robust onshore flow this weekend will help usher in
more moist air with min RHs back into the 30% to 40% range,
despite high temperatures remaining in the 80s.

While there is still some model discrepancy over how warm and dry
we will get next week, there is consensus that warm and dry
conditions will continue into the middle of next week, with the
flow switching to offshore by Tuesday as a thermal trough begins
to build along the coast. Fire weather concerns will be elevated
beginning Tuesday as minimum RH values look to drop into the 20%
to 30% range across much of the Cascades and the interior
lowlands south of Seattle. There may also be some locally breezy
east winds through the Cascade gaps. This pattern will continue
to be closely monitored.

62/15

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 6 AM PDT
     Saturday for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT
     Saturday for Admiralty Inlet.

&&

$$