Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
431
FXUS66 KSEW 190957
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
257 AM PDT Thu Mar 19 2026
.SYNOPSIS...
Atmospheric river will remain aimed at Western Washington
through Friday with a cold front stalled over Vancouver Island.
The river will come to an end as the cold front moves through
the area Friday evening. Zonal flow aloft over the weekend with
a weak system moving by to the north. Temporary break early Monday
before additional systems arrive Tuesday and Wednesday.
&&
.SHORT TERM /TODAY THROUGH SATURDAY/...
Satellite imagery shows long fetch of moisture extending from
east of the Hawaiian Islands into Western Washington. Doppler
radar indicating rain over most of the area with the rain shadow
over the Central Puget Sound trying to get reestablished.
Temperatures remaining mild with the clouds and rain, a couple
of degrees either side of 50 at 2 am/09z.
No changes to the short term forecast this morning. Atmospheric
river remaining over Western Washington with a cold front
stalled over Vancouver Island through Friday. IVT values steady
through the period, 500-700 kg/m/s. Little change in the snow
levels as well in the 7500-9500 foot range. Breezy conditions at
times with the front in the vicinity. Mild temperatures with
the moisture tap all the way down to near Hawaii, mostly in the
50s through Friday.
Cold front moving through Friday evening ending the atmospheric
river over the area. Steady rain turning to showers behind the
front. Windy along the Strait of Juan de Fuca into Whidbey
Island with a post frontal westerly push. Could see a brief
convergence zone over Snohomish County early Saturday morning.
Snow levels dropping quickly behind the front down to 3000-3500
feet with snow showers over all the passes but Snoqualmie. Lows
in the mid 30s to lower 40s.
Snow levels continuing to fall Saturday to around 2000 feet.
Moisture will be limited with just a chance of showers. For the
lowlands post frontal onshore flow keeping skies mostly
cloudy/partly sunny. High temperatures near the morning lows of
the last few days, near 50. Felton
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Weak system riding by to the north keeping chance or slight
chance pops in the forecast Saturday night and Sunday. A little
break in the weather Sunday night into Monday with a weak upper
level ridge moving through ahead of the next weather system.
Timing of the next system speeding up a little on the latest
run by a few hours with rain starting Monday night. Frontal
passage Tuesday with another system right on its heels for
Wednesday. The Monday night and Tuesday system will push snow
levels above the passes. Snow levels dropping down below pass
levels Tuesday night into Wednesday. Highs in the lower to mid
50s cooling to near 50 Wednesday. Lows mid 30s to lower 40s
except lower to mid 40s Tuesday morning.
&&
.AVIATION...
Westerly flow aloft will continue into Friday with a stalled frontal
boundary over Vancouver Island eventually pushing southeastward
across the area on Friday. Ceilings across the region remain a mixed
bag this morning with primarily MVFR conditions in light to moderate
rain expected to persist through the day.
KSEA...Expecting an overall low confidence forecast for the TAF
period as ceilings have been highly variable. Primarily MVFR
ceilings continuing into tonight in light rain at times. Surface
winds southerly 8 to 12 knots.
27
&&
.MARINE...
Periods of Small Craft southerlies will continue across the waters
late into the week as a frontal system remains stalled over
Vancouver Island. The frontal system will move over area waters on
Friday, with a westerly push through the Strait of Juan de Fuca
expected to reach potential gale force strength. Winds will ease
into the weekend as a building surface ridge offshore moves inland.
Another potent front will arrive Monday night into Tuesday.
27
&&
.HYDROLOGY...
Even with the atmospheric river aimed at Western Washington
rainfall amounts have not been that excessive. In the last 6
hours ending at 2 am/09z rainfall totals in the 0.30 to 0.60
inch range over the Olympics and Northern and Central Cascades.
Southern Cascades and lowlands less than 0.30 inches. Wettest
location has been along the coast with 0.60 to 1 inch of rain.
Rainfall totals for the last 24 hours more impressive with 1.5
to 3 inches over the Northern Cascades and Olympics, one to two
inches along the coast. The off and on rain shadow over the
Central Puget Sound has kept rain totals down to 0.10 to 0.50
inches.
Little change in the pattern through Friday with another 2 to 4
inches of rain in the North and Central Cascades and over the
Olympics. Snow levels remaining elevated, 7500 feet to 9500
feet. Steady rain will give way to showers and much lower snow
levels when the cold front moves through Friday evening.
Flood warning already up for the Snoqualmie, Snohomish,
Skykomish and Tolt rivers. These rivers have either crested or
will crest later today as a result of the lower rainfall rates
in the Central Cascades overnight. The Tolt, Skykomish and
upper reaches of the Snoqualmie have already receded below flood
stage. The lower reaches of the Snoqualmie as well as the
Snohomish will begin receding later today. Rainfall rates in the
mountains increasing this afternoon with the higher rates
continuing into Friday. This will create a double crest scenario
Friday afternoon or Friday evening pushing the rivers back
above flood stage.
In addition to the rivers in King and Snohomish county, a flood
watch will also remain in effect for Skagit and Whatcom county.
The reduced rainfall rates overnight have lowered the chances of
the Skagit at Concrete reaching flood stage this afternoon but
with the increasing rainfall later today there is still a good
chance the river reaches flood stage Friday. Same is true
downstream for the Skagit at Mount Vernon. Farther north the
Nooksack at Ferndale is forecast to crest a few inches below
flood stage Friday.
Last but not least, the Skokomish river in Mason county has been
underperforming so far but with another round of warm rain
coming up it is certainly possible the river gets to flood stage
later today or Friday. The watch for Mason county will also
remain in effect. Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through Friday afternoon for Cascades of Snohomish
and Northern King Counties-Cascades of Southern King
County-Cascades of Whatcom and Skagit Counties-City of
Seattle-Downtown Everett / Marysville Area-Eastside-
Foothills and Valleys of Central King County-Foothills
and Valleys of Pierce and Southern King Counties-
Foothills and Valleys of Snohomish and Northern King
Counties-Foothills and Valleys of the North Cascades-
Foothills of the Western and Southern Olympic Peninsula-
Lowlands of Pierce and Southern King Counties-Lowlands of
Western Skagit and Northwestern Snohomish Counties-
Lowlands of Western Whatcom County-Middle Chehalis River
Valley-Olympia and Southern Puget Sound-Olympics-
Shoreline / Lynnwood / South Everett Area-Southern Hood
Canal-Willapa and Black Hills.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for West
Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory until 5 AM PDT Friday for Admiralty Inlet-
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.
&&
$$
NWS SEW Office Area Forecast Discussion