Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS66 KSEW 090516 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 916 PM PST Fri Dec 8 2017 .SYNOPSIS...
-- Changed Discussion --
A strong upper ridge will maintain dry and stagnant conditions across Western Washington through next week. High clouds could increase this weekend as a frontal system passes by well to the north. Air quality will likely worsen over the next couple days.
-- End Changed Discussion --
&& .SHORT TERM...
-- Changed Discussion --
An upper ridge will remain over the Pacific Northwest through Monday for dry weather. The flow aloft will be southwest with the ridge axis centered over Eastern Washington. This will open the door for high clouds at times. An offshore frontal system will approach the coast Saturday and then skirt the area to the west and north Sunday but it will have little affect on the local weather. Winds are generally light with low level easterly flow. This means fog should be more prevalent tonight for the interior lowlands, especially the central and south interior closer to Puget Sound. Fog should also be slower to burn off Saturday and some areas could be foggy all day. Areas that don`t get fog tonight will be frosty again. More of the same is likely Sunday and Monday although high clouds might lessen fog coverage a bit. Stagnant conditions will also lead to slowly worsening air quality over the weekend. An air stagnation advisory is in effect through Monday for most of the interior lowlands. Schneider .LONG TERM...Previous discussion...Dry weather will continue through at least Thursday as the ridge begins to weaken. By Friday, showers return as the flow aloft turns more zonal. Showers will continue into the weekend with moist west to northwest flow over the area. Temperatures are trending close to normal over this period. 33
-- End Changed Discussion --
&& .AVIATION...
-- Changed Discussion --
A strong upper ridge axis will continue over Central and Eastern Washington through Saturday night, with light to moderate southwest flow aloft over Western Washington. The air mass will be dry and very stable. Shallow dense fog over the Puget Sound lowlands will be the main concern. Occasional high clouds and cirrus will further complicate the fog forecast due to its temporary retardation of surface cooling and the inability that it creates to monitor nighttime fog with satellite imagery. In general, changes in fog coverage will be slow to occur. KSEA...The terminal`s hilltop location means that shallow dense fog in the vicinity of the terminal will occasionally cross the airfield and reduce visibility, then drift on with breaks. In terms of fog, it is a bit like being on a low island, sometimes a sandbar. So fog at SEA through Saturday morning will be a cat- and-mouse game, with little skill in determining exactly when the fog will ebb and flow. Nearby BFI and RNT should stay constantly socked in with fog through Sat morning. More substantial improvement should occur around noon or 1 pm (20z or 21z) on Saturday.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Easterly gradients will continue through this weekend due to a strong 1040 mb surface high over Eastern Washington and lower pressure offshore. East wind in excess of 20 knots will occur at times at the West Entrance and parts of the coastal waters. The offshore flow will weaken and become southerly on Monday.
-- End Changed Discussion --
&& .HYDROLOGY...River flooding is not expected during the next week. && .SEW WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
WA...Air Stagnation Advisory until noon PST Monday for Admiralty Inlet Area-Bellevue and Vicinity-Bremerton and Vicinity- East Puget Sound Lowlands-Eastern Strait of Juan de Fuca- Everett and Vicinity-Hood Canal Area-Seattle and Vicinity- Southwest Interior-Tacoma Area-Western Skagit County- Western Whatcom County. PZ...Small Craft Advisory until 3 AM PST Sunday for 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 Point Grenville To Cape Shoalwater 10 To 60 Nm. Small Craft Advisory from 3 AM to 3 PM PST Saturday for Coastal Waters From James Island To Point Grenville Out 10 Nm- Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Small Craft Advisory until 5 PM PST Saturday for West Entrance U.S. Waters Strait Of Juan De Fuca.
-- End Changed Discussion --
&& $$ www.weather.gov/seattle

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.