748
FXUS66 KSEW 111605
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
905 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/...The forecast remains on
track, with no significant updates needed to the short and long
term or fire weather this morning. The previous discussion
follows below, with updates made to the aviation and marine
sections. 14

A high pressure ridge building offshore will influence 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 along the the
coast. 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 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/McMillian

&&

.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/Strait of Juan de Fuca through 18Z
(11 AM PDT).

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/McMillian

&&

.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...Dense Fog Advisory until 11 AM PDT this morning for Central U.S.
     Waters Strait Of Juan De Fuca-Coastal Waters From Cape
     Flattery To James Island Out 10 Nm-Coastal Waters From
     James Island To Point Grenville Out 10 Nm-Coastal Waters
     From Point Grenville To Cape Shoalwater Out 10 Nm-East
     Entrance U.S. Waters Strait Of Juan De Fuca-Grays Harbor
     Bar-West Entrance U.S. Waters Strait Of Juan De Fuca.

     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.

&&

$$