textproduct: Seattle/Tacoma

SYNOPSIS

A weak upper ridge will provide a brief period of drier weather before the next system arrives late Saturday. Moderate to heavy rain is expected at times Saturday night into Monday night along with snow levels rising above pass level. Area rivers are expected to rise with flooding expected on the Skokomish. Drier conditions are favored to return by the middle of next week as high pressure aloft rebuilds into the region.

SHORT TERM /TODAY THROUGH SUNDAY/

A weak upper ridge will slide onshore today for a brief trend toward drier conditions. The ridge axis will move east of the Cascades tonight and another frontal system will approach the coast Saturday morning. Rain will spread inland Saturday evening as a warm front lifts northward toward the area. Snow levels will rise above all of the passes on Sunday as the warm front lifts northward and an atmospheric river takes aim at British Columbia and Western Washington. Heaviest precipitation, initially, will be along the coast, in the Olympics, and across the North Cascades.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Periods of moderate to locally heavy rainfall will continue into Monday as the axis of heaviest precip is projected to shift southward slightly. In addition to the precipitation, a period of breezy to locally windy conditions is expected Sunday night into Monday. With the heavier precip, there will also be an elevated landslide risk. Ensembles are in good agreement with a shift toward drier and rather mild conditions taking hold around the middle of next week as high amplitude upper ridging takes up residence along the west coast of the lower 48.

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AVIATION

Upper level ridge centered offshore moving through the area today into tonight. Ridge axis east of the Cascades by 06z Saturday. Front moving into the area later Saturday. Northwesterly flow aloft switching to southwesterly tonight. In the lower levels, light onshore flow becoming light offshore flow this evening.

MVFR ceilings this morning with patchy LIFR mainly Kitsap peninsula. Conditions improving this afternoon. VFR conditions tonight with just some high clouds. Areas of fog forming after 06z Southwest Interior and south Puget Sound with visibility below a mile until around 18z Saturday.

KSEA...MVFR ceilings through the morning hours. Stratus layer scattering out mid afternoon leaving just some high clouds. Fog in the vicinity of the terminal 12z-18z Saturday. Southerly wind 6 to 10 knots becoming southeast 4 to 8 knots 03z-06z. Felton

MARINE

High pressure over the waters today and tonight will weaken Saturday as a front moves through the area. Additional systems will move through the northern portion of the waters Sunday and Monday. High pressure will rebuild Tuesday.

Small craft advisories for the coastal waters and West Entrance to the Strait of Juan de Fuca for seas 10 to 12 feet today and for a combination of southeasterly winds 20 to 25 kt and seas building to 12 to 17 feet tonight through Saturday into Saturday night. Small craft advisory winds continuing through Sunday night before subsiding Monday. Seas slowly subsiding Sunday through Monday but not dropping to near 10 feet until Tuesday. Felton

HYDROLOGY

No river flooding is expected through Saturday. Ensemble precipitation guidance continues to trend up leading to an increased concern for potential river flooding. The main risk of river flooding is along the Skokomish River in Mason County, where the forecast crest is just below moderate flood stage Monday. Elsewhere, rivers will rise but confidence in rivers reaching flood levels is less than 30%. The relative risk appears to be highest for rivers originating from the central and northern Cascades, where snow levels will rise from around 4000 feet to 7500-8000 feet during the event, bringing rain on snow into the picture.

This event is likely to be followed by a relatively dry period, allowing for rivers to recede mid to late next week.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 6 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 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- West Entrance U.S. Waters Strait Of Juan De Fuca.