textproduct: Seattle/Tacoma

SYNOPSIS

Lingering showers remain across the region this evening, with snow expected down to around 1500 ft. For the lower elevations, expect some snow mixing in with rain except for some light snow within a Puget Sound Convergence Zone. Showers diminish by early Saturday, with high pressure beginning to build over the region. This will maintain drier conditions, with a fog likely to develop for the next several mornings. A return to a more typical pattern oflowland rain and mountain snow is expected late this week.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

Forecast remains on track tonight with enhanced showers within a Puget Sound Convergence Zone bringing brief downpours to portions of southern Snohomish and far northern King counities this evening. For areas east of I-5, some light snowfall accumulations around an inch or two have been reported in the US 2 corridor as far west as near Sultan. This has largely be attributed to the heavy precipitation rates cooling temperatures and pulling snow down closer to the surface in these areas. Elswhere, snow levels are generally lowering to near 1500 ft as colder air filter into the region. Will continue to have a risk of this new precipitation freezing overnight through early tomorrow morning as temperatures drop below freezing. Use extra caution on any elevated, untreated surfaces if venturing out late tonight or early Saturday morning as patches of ice may be present. Remainder of previous short term section remains valid and follows. 12

Another item to monitor overnight into Saturday will be some increased outflow through the Fraser River valley. With cooler temperatures and modest winds across western Whatcom County we could see some wind chill values between 12-20 degrees. As such we have opted to issue a Cold Weather Advisory for that area starting early Saturday morning through noon.

Conditions will remain cool and mostly dry through Tuesday/Tuesday night as upper level ridging dominates the pattern. Given recent rains, saturated conditions near the surface could lead to the development of fog the next few mornings. This will need to be monitored for dense fog potential.

LONG TERM /MONDAY THROUGH FRIDAY/

Ridging begins to flatten Wednesday onward and the the door begins to open to additional weather systems moving through the region. At this point in time, it appears that this pattern will be fairly nominal for the area with chances for lowland rain, mountain snow, and occasional breezy conditions. At this point in time there isn't a strong signal for any major events over the next week. -Wolcott-

AVIATION

Westerly flow aloft will become more northwesterly by tonight and persist through Saturday. Low level onshore flow peaks this evening, with a Puget Sound Convergence Zone remaining active near KPAE. Expect a continue mixe of conditions with widespread showers slowly fading out and the aforementioned PSCZ remaining active overnight. This will maintain lower conditions generally south of KPAE and north of KBFI tonight. Elsewhere, breezy southerly winds with gusts to 20 kt linger this evening, easing into early Saturday. Weak Fraser Outflow may bring some gusty northeasterly winds to 25 kt to KBLI late tonight through 18Z Saturday.

With low levels remaining moist from recent rains, any areas of clearing overnight will also bring periods of fog to some terminals by Saturday morning. Cool overnight temperatures near freezing may even promote some spots of freezing fog early Saturday morning, especially for South Sound terminals including KOLM.

KSEA...MVFR ceilings this afternoon with southerly winds persisting between 10-20 kt, with gusts to 25-30 kt. Southerly winds will ease to 5-10 kt again by this evening. Could see a brief improvement in ceilings towards VFR for a few hours this evening, but expect ceilings to fall back to down to MVFR overnight into early Saturday. At this time, convergence zone activity looks to stay north of the terminal.

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MARINE

Small craft strength northwesterly winds will continue across the coastal waters into Saturday in the wake of a weak surface trough that continues to push inland this afternoon. Westerly winds along the Strait of Juan de Fuca have also increased to 20-30 kt and will remain gusty through late tonight, before easing Saturday morning. Small craft conditions will persist across the coastal waters through Saturday, however, as seas currently at 10-12 ft continue to build towards 13-16 ft by late tonight.

A brief period of weak Fraser Outflow will also be possible tonight into Saturday morning and may bring 15-20 kt northeasterly winds, with occasional gusts to 25-30 kt, to the northern portions of the Northern Inland Waters at times.

High pressure will build back into the area waters this weekend and remain situated across the region into early next week. Dense fog may develop over the interior waters with clearing conditions and light winds during the overnight periods and will likely restrict visibilities at times. Seas will gradually subside to 3-6 ft for a brief period on Sunday, though systems passing by to the north will allow for seas to build back to 6-9 ft by Monday.

The ridge will weaken on Tuesday, with the next front looking to drop down into the coastal waters around midweek.

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HYDROLOGY

No river flooding is expected during the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 4 AM PST Saturday for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County- Cascades of Whatcom and Skagit Counties.

Cold Weather Advisory from 1 AM to noon PST Saturday for Lowlands of Western Whatcom County.

PZ...Small Craft Advisory until 6 PM PST Saturday 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.

Small Craft Advisory until 1 AM PST Saturday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.