Des Moines, Washington Weather Forecast Discussion

718
FXUS66 KSEW 191619
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
919 AM PDT Fri Sep 19 2025
.SYNOPSIS...Dry and mild conditions will continue today ahead of
widespread rain, breezy winds, and cooler temperatures over the
weekend. Conditions will dry out early next week as high pressure
builds into the region, with chances for more precipitation mid
week.
&&
.SHORT TERM /TODAY THROUGH SUNDAY/...Weak high pressure over the
region today for generally mild weather. Smoke from the Bear Gulch
fire continues to drift south and over southern Mason County where
there are pockets of degraded air quality. Smoke will drift east
tonight and over the Seattle metro but we will see conditions
improving through Saturday with the incoming frontal system. 33
Previous discussion...High pressure will build inland today as a
weak trough shifts east of the Cascades. Temperatures will warm
up a few degrees with highs in the 70s across the lowlands and in
the 60s along the water. Skies will remain clear through the
afternoon, with marine stratus creeping inland along the coast by
the evening as onshore flow increases. However, smoke from area
wildfires will continue to cause hazy conditions across western
Washington.
The next weather system will enter the region later on Saturday,
swinging a cold front inland. Rain will fill in along the coast by
the afternoon and cross the region in the evening into Sunday
morning. Most areas will dry out by Sunday afternoon, with
forecast models suggesting the formation of post-frontal
convergence zone showers over the central Puget Sound. Rainfall
totals over the weekend are on track to range from 0.25 to 0.50
inches over the lowlands, and generally 0.50 to 1.50 inches over
the mountains. Alongside rain, the incoming cold front will bring
locally breezy winds around 20 to 30 mph, as well as cooler
temperatures on Sunday that will peak in the 60s for most areas.
15
.LONG TERM /MONDAY THROUGH THURSDAY/...High pressure will build
inland in the beginning of next week, bringing warmer and drier
conditions to the region. Chances for rain increase towards the
middle of next week, with potential for cooler conditions and more
widespread precipitation.
15
&&
.AVIATION...Northerly flow aloft becoming more zonal later this
morning. Clear skies this morning over Western Washington. Most
terminals are VFR. Visibility has improved at the terminals that
received fog this morning, with the exception of HQM. Conditions are
slowly improving at HQM and expecting the fog to burn off after
after 17z-18z. Clear skies will prevail through the day today.
Models are more confident on marine stratus forming along the coast
Saturday morning. Mostly calm winds this morning, becoming northerly
at 5-10 kt.
KSEA...VFR conditions with clear skies through the TAF period. Winds
NNE at 5 kt or less becoming NW after 18z at 7-10 kt.
62/29
&&
.MARINE...High pressure will remain over the coastal waters today.
It will begin to weaken tonight as a frontal system moves through
the waters Saturday night into Sunday. Southwesterly winds will
increase ahead of the front on Saturday, with the strongest winds
associated with the frontal passage Saturday night into Sunday
morning. The areas with the best chance of seeing Small Craft
Advisory winds will be through the central Strait of Juan de Fuca,
though winds my briefly reach criteria throughout the interior
waters as the front moves through. A push of westerly winds will
follow behind the front for Sunday, with more SCA winds through the
central Strait of Juan de Fuca. High pressure rebuilds on Monday
before another weakening front approaches the coastal waters on
Tuesday.
Seas around 4 to 6 ft today will increase back to 7 to 9 ft through
the weekend. Seas will hover around 6 to 8 ft through early next
week.
62
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$

NWS SEW Office Area Forecast Discussion