Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
711
FXUS66 KSEW 132215
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
315 PM PDT Fri Mar 13 2026
.SYNOPSIS...
A stationary front over the Columbia River will begin to move
out of the region this weekend. Widespread precipitation will
decrease in coverage into Saturday, with a convergence zone
continuing to affect portions of the Cascades and adjacent
foothills. Warmer temperatures are on the way next week,
although the pattern will continue to remain unsettled with
additional systems passing through with more widespread rain.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
The synoptic pattern remains relatively intact, with a
stationary front along the Columbia River, and a strong zonal upper
level jet over the state expanding over the northern CONUS. A
shallow shortwave trough will pass through Saturday afternoon,
with a ridge beginning to build over the Pacific late this
weekend.
Precipitation: Widespread stratiform showers continue on radar
this afternoon. The precipitation has transitioned from snow to
rain in spots as temperatures struggle to climb into the upper
30s this afternoon (many spots will likely remain in the mid
30s). The ensembles have the stratiform precipitation
diminishing from north to south this evening. A convergence zone
is expected to setup across the foothills/west slopes of the
Cascades tonight into the first part of Saturday. The overall
moisture output from this convergence zone will be significantly
less than the precipitation past 24 hours. The temperatures
tonight however will be a couple degrees cooler in spots, with
lows right around freezing (areas closest to water will see lows
in the mid 30s, and mountain areas with fresh snow will see lows
in the teens).
For impacts: the heavy snow threat has ended for the Olympics
this afternoon, and the winter storm warning was subsequently
cancelled. Snow showers will continue, but are not expected to
produce any significant impacts. For the Cascades, heavy snow is
expected to continue on the west slopes through tonight. Travel
continues to remain dangerous in the passes with several
roadways experiencing closures at times today. The winter storm
warning will continue into Saturday morning, with travelers
encouraged to check road conditions on WSDOT before traveling.
Hi-res ensemble guidance was keeping a medium to high chance of
central Cascade foothill and valley locations receiving an
additional 1-2 inches of snow through Saturday morning with the
convergence zone. Given the lower snow levels in this area, and
the impacts from this morning`s snow, the winter weather
advisory was extended through 11 AM for the King/Pierce County
areas, and expanded to include a portion of the foothills
extending into southern Snohomish County. Snow in these areas
will be dependent on the location that the convergence zone sets
up. Remaining lowland areas have a low probability of seeing any
accumulating snow (let alone a trace), but may still see
snowflakes come down tonight for any shower that moves through.
The precipitation will wrap up Saturday evening, with a break in
any moisture for the majority of the day until Sunday evening
(a 30% chance of snow showers will continue in the mountains).
Temperatures will warm considerably from Friday into Saturday
and Sunday, with highs returning into the mid 40s. Lows will
still remain around freezing for most through the weekend. Winds
will vary at times between the south and north, but generally
remain around 5 to 10 mph.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
There are strong signals that the following week will continue
to remain active, as ensembles continue to point to a warmer and
wet pattern continuing into next week. Weak atmospheric river
conditions are expected to continue as the jet stream remains on
the west coast, but shifts north into northern WA/southern B.C.
next week. The main concern will be potential hydro impacts from
higher snow levels from the warm air moving in, and some snow
melt from recent snows. See the hydrology section below for
additional details on river flooding. The precipitation is
primarily focused in the mountains, and the coast. Temperatures
will climb through the week, with highs approaching upper 50s to
60 towards Wednesday through Friday.
HPR
&&
.AVIATION...
Stalled frontal band still giving a narrow ribbon
of light snow across western WA, primarily over southern King
and into Pierce counties. The trend is to still transition to a
rain/snow mix then all rain moving through the rest of the
afternoon and evening as the band shifts south and exits.
Showers will then reform over the central sound overnight with a
weak convergence zone. Light rain or a rain/snow mix possible
near the sound with snow heading east toward the Cascades.
Showers will taper off by 14-18Z as high pressure moves in. LIFR
to IFR in the central sound with the snow and convergence zone,
with primarily MVFR otherwise.
KSEA...Snow changing to a mix or light rain by 00Z. Models favor
light rain with convergence zone overnight with higher snow
levels. Surface temps remaining above freezing. Winds light and
variable, switching to S to 10 kt by 09-12z. IFR improving to
MVFR 15z and VFR after 18z. 33
&&
.MARINE...
A stalled front near the Oregon border this afternoon will shift
southeastward tonight and Saturday as a surface ridge builds into
the coastal and offshore waters. This will lead to increasing
onshore flow over the coastal waters and in the Strait of Juan de
Fuca tonight into Saturday. The ridge will shift onshore Saturday
night and Sunday as a strong warm front approaches the offshore
waters. The warm front will lift northward across area waters
Monday into Tuesday for increasing winds and seas.
27
&&
.HYDROLOGY...
Flood Watches remain in effect for SW Washington
including Grays Harbor, Thurston and Lewis counties due to
potential flooding. Both the Newaukum River near Chehalis and
the Skookumchuck River near Bucoda have reached flood stage,
with the Chehalis at Grand Mound following early Saturday.
Rivers will crest this weekend.
An atmospheric river is expected to move inland to the north
early next week. This could bring additional flooding concerns
to portions of the area as several rivers are forecast to reach
Action Stage. For now, the only river forecast to reach flood
stage is the Skokomish River.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning until 5 AM PDT Saturday for Cascades of
Pierce and Lewis Counties-Cascades of Snohomish and
Northern King Counties-Cascades of Southern King County-
Cascades of Whatcom and Skagit Counties.
Flood Watch through Sunday afternoon for Cascades of Pierce
and Lewis Counties-Foothills and Valleys of Thurston and
Lewis Counties-Foothills of the Western and Southern
Olympic Peninsula-Grays Harbor County Coast-Lower
Chehalis River Valley-Lowlands of Lewis and Southern
Thurston Counties-Middle Chehalis River Valley-Olympia
and Southern Puget Sound-Olympics-Willapa and Black Hills.
Winter Weather Advisory until 11 AM PDT Saturday for Foothills
and Valleys of Snohomish and Northern King Counties.
Winter Weather Advisory until 11 AM PDT Saturday for Foothills
and Valleys of Central King County-Foothills and Valleys
of Pierce and Southern King Counties.
PZ...Small Craft Advisory from 11 PM this evening to 11 PM PDT
Saturday for Central U.S. Waters Strait Of Juan De Fuca-
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-West
Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 11 PM this evening to 3 PM PDT
Saturday for East Entrance U.S. Waters Strait Of Juan De
Fuca.
&&
$$
NWS SEW Office Area Forecast Discussion