textproduct: Seattle/Tacoma

SYNOPSIS

A frontal system will continue to bring lowland rain and higher elevation mountain snowfall into early Saturday. Drier conditions will develop late Saturday through Sunday. Cooler temperatures, along with periods of unsettled weather, are expected at times Monday through midweek with deep troughing over the Western US.

SHORT TERM /TODAY THROUGH SUNDAY NIGHT/

A passing weak front has crossed the Sound and, as per latest radar, continues to make its way east out of the area. While activity has settled over the Olympic Peninsula, scattered showers are present over the nearshore coastal waters, thus leaving the door open for additional precip overnight tonight. Precip amounts both with the front and behind it with most locations seeing 0.25 of an inch per radar estimates.

Inherited forecast remains on track with no evening updates needed. For additional forecast details, please refer to the Previous Discussion section below. 18

From Previous Discussion...A front is continuing to move across Western Washington this afternoon, bringing steadier lowland rain and higher elevation mountain snowfall. Precipitation will continue at times through Saturday, although the bulk of the stratiform precipitation will move east of the Cascades by tonight. Snow levels around 3500 to 4000 feet this afternoon will fall to 2000 feet on Saturday. This will result in light to moderate snow accumulation for the Cascades, with total accumulation amounts of 2 to 5 inches for Snoqualmie and Stevens Pass, and near 7 to 10 inches for Mount Baker.

Drier weather will return on Sunday as the bulk of the precipitation associated with an upper low offshore is focused into California. Some clearing on Sunday may result in areas of fog Sunday morning. Otherwise, highs will range in the mid to upper 40s this weekend.

LONG TERM /MONDAY THROUGH THURSDAY/

A pattern change begins on Monday as deep upper troughing dives southwards and becomes situated offshore of the Pacific Northwest. This will promote the return of unsettled weather for Western US. Predominantly, this will lead to colder temperatures for next week, especially the overnight lows. Forecasted low temperatures for next week range in the upper 20s to mid 30s for an extended period due to continued troughing. In addition, precipitation is expected to spread northwards early Monday, as the trough deepens offshore. There remains uncertainty in the exact location and intensity of any precipitation on Monday, but a rain/snow mix can't be ruled out at this point, dependent on the precipitation rates. However, temperatures will be marginal, and with likely south flow at the surface, little to no accumulation is expected in the lowlands. We'll continue to monitor this feature on Monday. Deep upper troughing will then remain focused over the Western US into midweek, with continued light precipitation at times. This pattern will also promote additional mountain snowfall, as the cooler pattern continues into the extended period. JD

AVIATION

Main rain band with a frontal system will push into the Cascades this evening with scattered showers behind through the rest of night. Showers becoming more isolated moving into Saturday afternoon with a weak trough overhead. Mainly MVFR conditions through Saturday morning with clouds lifting to VFR in the afternoon.

KSEA...MVFR conditions tonight with rain ending 06-08Z. S/SW winds 10 knots, decreasing to 3 to 6 knots overnight, becoming light N by 00Z Sun. 33

33/Mazurkiewicz

MARINE

Elevated seas continue. Brief surface high pressure builds over the weekend for northerly flow over the area waters. A series of troughs look to dig over the coastal waters early next week which will bring unsettled conditions over the water throughout the week.

Coastal seas generally in the 10 to 15 feet range this evening and will slowly decrease throughout Saturday. Seas look to get below 10 feet on Sunday before building back upwards to 9 to 13 feet by Tuesday.

33/Mazurkiewicz

HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 10 PM PST this evening for Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-Grays Harbor Bar.

Small Craft Advisory until 10 AM PST Saturday 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.