textproduct: Seattle/Tacoma

SYNOPSIS

An upper level ridge will lead to dry and mild conditions into early next week along with varying amounts of night and morning fog across the lowlands.

SHORT TERM /TODAY THROUGH THURSDAY/

Apart from a few lingering showers across the far north and coastal areas, precipitation has all but ended as upper level ridging begins to strengthen over the region. The air mass remains quite mild and high temperatures could approach daily records in a few spots today. The ridge will temporarily flatten on Wednesday as a weak system passes to our north, but it will have little perceptible affect on our weather. Surface gradients will remain relatively light through much of the short term forecast period which will likely allow low clouds and fog to become more widespread over the next few nights and mornings across much of the lowlands.

A strong upper ridge axis will take up residence just offshore on Thursday. Near the surface, high pressure will strengthen over the interior of British Columbia while thermally induced low pressure creeps northward along the Oregon coast. This will lead to increasing northerly or offshore flow across Western Washington Thursday afternoon and evening. This should help some areas stand a better chance of some sunshine, but the low clouds could stubbornly hang on most of Thursday for places like the Southwest Interior and south Puget Sound. High temperature forecasts for Thursday across the lowlands will be a little tricky based on how much low cloud clearing does or doesn't occur.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

The upper ridge axis remains firmly in place Friday into Saturday with varying degrees of low level offshore flow. Day to day fog coverage will be the primary forecast challenge, but coastal and mountain areas will likely see wall to wall sunshine and very mild daytime temperatures. Models shift the ridge axis onshore and weaken it somewhat early next week. Dry conditions will continue, but the return of weak surface gradients should result in expanded night and morning fog coverage for the lowlands areas.

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AVIATION

Westerly flow aloft continues through this afternoon as an upper ridge builds into Western Washington. Widespread MVFR/IFR cigs early this morning with abundant moisture at the lower levels. MVFR/IFR cigs will continue into the morning, with LIFR cigs at times along the coast. Areas of fog may also develop into the morning hours, mainly along the Olympic Peninsula and in the vicinity of PWT/OLM. Some improvements in cigs may occur early this afternoon , mainly from PAE southwards and towards the Cascade Foothills. Otherwise, MVFR/IFR cigs will likely continue at times through the afternoon elsewhere. LIFR/IFR cigs and vsbys will become more widespread by late evening with light flow at the surface, and expected fog development. Dense fog will then be likely Tuesday night into Wednesday. Light surface winds through today.

KSEA...MVFR cigs will continue into Tuesday morning. There also remains approximately a 20 to 25% chance of IFR cigs into the morning as well. Some improvements to VFR will be possible by late morning into the early afternoon. However, widespread LIFR conditions are then anticipated to return by tonight. There is high confidence in fog development tonight into Wednesday morning, with LIFR conditions potentially as early as 01-03z, with greater confidence after 05-06z. Light S/SE surface winds will become light northerly this afternoon. JD

MARINE

Surface high pressure will expand northward across area waters today. A weak frontal boundary will dissipate well offshore Wednesday afternoon followed by strong surface high pressure over the offshore waters shifting into the interior of British Columbia on Thursday and a period of offshore flow toward the end of the week. Apart from easterlies near gaps in coastal terrain, this should be a relatively quiet period in terms of wind across area waters.

Coastal seas will remain near 10 feet this morning, subsiding during the afternoon and evening. Another decaying swell train continues to be forecast to push seas back above 10 feet Wednesday before subsiding again Thursday into the weekend. 27

HYDROLOGY

The Skokomish River continues to slowly recede early this morning, but will remain in minor flood stage into Wednesday. A Flood Watch remains in effect for Whatcom and Skagit Counties. The Skagit River looks to crest below flood stage into this morning. The Nooksack River at Ferndale continues to slowly rise, but may crest just below flood stage as well today.

Drier weather is then expected through next weekend, with no additional flooding expected. JD

SEW WATCHES/WARNINGS/ADVISORIES

WA...Flood Watch until 10 AM PST this morning for Cascades of Whatcom and Skagit Counties-Foothills and Valleys of the North Cascades-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County.

PZ...Small Craft Advisory until 10 AM PST this morning 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 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-Grays Harbor Bar.