textproduct: Seattle/Tacoma

SYNOPSIS

Weak ridging builds into Western Washington early Sunday. An upper trough digs southwards along the coast late Sunday into Monday. Ridging builds back into the northern Pacific Northwest Tuesday and Wednesday. Troughing returns late week.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/

A post-frontal airmass continues this afternoon with predominantly mostly sunny conditions. The exception being an area of weak convergence that continues over portions of central Puget Sound. Drier conditions will continue to develop into tonight as clouds taper off this evening. Mostly clear skies and lighter winds early Sunday AM will promote fog development, particularly in the usual areas and river valleys.

A weather system approaches the west coast late Sunday and Monday with the bulk of the energy digging southwards towards California early next week. Dry conditions continue on Monday due to the system being well offshore. Clouds will spread across Western Washington during this period. Otherwise, highs will be in the mid 50s to low 60s Sunday and Monday.

LONG TERM /TUESDAY THROUGH SATURDAY/

Upper ridging develops over British Columbia Tuesday and Wednesday with an upper low positioned well south of Western Washington, mainly offshore of central California. Dry conditions are expected Tuesday and Wednesday. AM fog will develop again both Tuesday and Wednesday morning with relatively light winds and clearer skies. In addition, areas of frost are expected each morning, mainly away from the water. Ensembles are consistent in the return of weak troughing Thursday into late week, bringing precipitation chances to the area, although rainfall amounts are not heavy due to the weakening nature of any frontal system. Temperatures look to remain near normal during this period, with highs peaking midweek. JD

AVIATION

West to northwest flow aloft will continue into Sunday morning before backing southwesterly in response to an upper trough diving southward over the offshore waters. Low level onshore flow will gradually weaken this afternoon into tonight then become northerly or weakly offshore on Sunday. Ceilings within what is left of the convergence zone are mostly VFR this afternoon and will continue to lift and scatter out this afternoon and evening. Light surface winds and low level moisture will lead to the formation of IFR/LIFR fog and low clouds on Sunday morning...especially across the Southwest Interior and south portions of Puget Sound. Low clouds will lift for another VFR afternoon on Sunday under varying amounts of high level cloud cover.

KSEA...VFR ceilings remain this afternoon under the remnants of a convergence zone. Expect this to lift and scatter out late this afternoon and evening. Confidence remains fairly high that some LIFR fog and low clouds will be around the terminal on Sunday morning before scattering out by afternoon. Surface winds generally N/NE 5 to 8 knots.

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MARINE

Surface high pressure will build across the waters tonight into Sunday in the wake of a frontal system that moved across the waters earlier today. A low pressure system passing southward well offshore will turn winds northerly or weakly offshore Sunday into Monday. Weak high pressure will remain across the waters into the middle of the coming week for rather quiet conditions. A larger swell train near 10 feet generated by active weather well offshore is expected to reach the coastal waters around Thursday.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 6 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 8 PM PDT this evening for Coastal Waters From Cape Flattery To James Island 10 To 60 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.