Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
375
FXUS66 KSEW 290311
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
811 PM PDT Mon Sep 28 2026
.SYNOPSIS...A frontal system will move across Western Washington
tonight through Tuesday with increasing rain and breezy winds.
Upper ridging begins to build over the Pacific Northwest
Thursday and Friday with just a slight chance of precipitation.
The upper ridge further builds next weekend for drier, warmer
conditions.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...No significant
changes made to the forecast this evening. The previous
discussion can be found below along with updates to the aviation
and marine sections:
Mid and high clouds continue to increase this afternoon across
the area ahead of an approaching frontal system. Rain will begin
to spread along the northern coast this evening, with rain
becoming more widespread for areas north of Snohomish County
tonight. The front drifts southwards on Tuesday, with rain
moving from north to south by the afternoon. Rainfall amounts
will be heaviest across the western slopes of the Olympic
Peninsula, Skagit and Whatcom Counties, as well as the Cascades
from King County northwards. Generally 1 to 3 inches of rain is
expected for the mountains, with 0.50-1.25 inches in the
lowlands of Skagit and Whatcom Counties. Significantly lighter
QPF from Seattle southwards as the front weakens.
The more impactful aspect to this system will be the increasing
southerly winds tonight through Tuesday. South winds are
expected to be strongest over western Whatcom County, with gusts
of 35 to 45 MPH. Gusty south winds are also expected for the San
Juan Islands, western Strait of Juan de Fuca, and a region from
Hood Canal to Everett, where gusts of 30 to 40 MPH are
anticipated. Elsewhere, winds will be breezy, ranging 25 to 35
MPH. Due to the continued foliage on trees, gusty winds may
cause localized power outages and tree limb damage. Winds will
slowly subside later Tuesday into Tuesday night for most areas,
the exception being a westerly push through the Strait of Juan
de Fuca late Tuesday.
An upper ridge slowly begins to build over the Pacific Northwest
on Wednesday, resulting in drier conditions. Areas of stratus
and morning fog may occur Wednesday AM due to residual moisture
at the surface. Temperatures will be cooler Tuesday and
Wednesday in the low to mid 60s.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...Zonal flow aloft
continues Thursday into Friday. A system will weaken as it
approaches Western Washington during this period, resulting in
just a slight chance of precipitation at this time, mainly for
northern areas. Ensembles are in general agreement in the ridge
becoming more pronounced across the Western US this weekend,
resulting in drier and warmer conditions. Some uncertainty in
the ensembles in regards to the return of more onshore flow
early next week, but overall, warmer and drier conditions are
expected during this period. JD
&&
.AVIATION...
Westerly flow aloft will increase overnight as a frontal system
offshore moves into the region during the day on Tuesday.
Ceilings will deteriorate overnight with rain along the coast
spreading into the North Interior late this evening then
southward on Tuesday morning. Widespread IFR or low MVFR ceilings in
rain are expected to develop 09Z-12Z and persist through much of
Tuesday. Gusty southerly surface winds will develop tonight and
continue into early Tuesday afternoon. Gusts of 30 to 40 knots are
expected from KPAE northward with 20 to 30 knots at times across the
remainder of the area.
KSEA...MVFR ceilings expected to develop around 10-12z as rain
spreads into the area. Ceilings are expected to become IFR at times
toward late morning. Ceilings will marginally improve Tuesday
evening as a front gradually shifts east of the area. Southerly
surface winds 10 knots will rise to 15 to 20 knots overnight with
occasional gusts of 25 to 30 knots between 09Z and 18Z. Winds ease
mid to late afternoon Tuesday.
27
&&
.MARINE...
A front approaching the coastal waters will shift inland during
the day on Tuesday. Headlines remain in effect for all waters with
low end gale conditions expected across the Northern Inland
waters later tonight into Tuesday morning. A brief increase
in onshore flow will follow the front Tuesday evening before quickly
diminishing by early Wednesday. Surface high pressure building over
the interior of British Columbia and weak troughing just offshore
will lead to some weak east/southeast flow on Thursday. Thermally
induced surface low pressure begins to expand northward along the
coast toward the weekend for northerly or weak offshore flow across
area waters.
27
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 2 AM to 2 PM PDT Tuesday for Lowlands of
Western Whatcom County-San Juan County.
PZ...Small Craft Advisory until 5 PM PDT Tuesday 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-
Puget Sound and Hood Canal-West Entrance U.S. Waters
Strait Of Juan De Fuca.
Small Craft Advisory until 5 AM PDT Wednesday for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
Gale Warning from 11 PM this evening to 5 PM PDT Tuesday for
Northern Inland Waters Including The San Juan Islands.
&&
$$
NWS SEW Office Area Forecast Discussion