textproduct: Seattle/Tacoma

SYNOPSIS

Drier conditions will linger tonight into Saturday for much of the region. Widespread precipitation - lowland rain, mountain snow - with breezy winds will move into the area from the North Saturday night into Sunday. Cooler and unsettled weather will continue into Monday, with an increased potential for an organized system mid week into the Thanksgiving Holiday.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

A frontal system over British Columbia will kick off the weekend, resulting in increased clouds over western Washington and some rain at times across the northern Olympic Peninsula and northern interior. Onshore flow will increase Saturday afternoon with breezy winds along the northern coast and Whidbey Island northward. This will also preclude the relatively slow shift of the system over British Columbia southward into western Washington Saturday night into early Sunday morning. This will bring widespread precipitation and breezy winds through Sunday. Snow levels Sunday morning will start around 5500-6000 ft gradually lowering to near 2000-2500 ft late Sunday night. This will set the stage for expected accumulations across all the mountain passes with a 60-70% chance of 1-2 inches by 10PM Sunday night.

LONG TERM /MONDAY THROUGH FRIDAY/

Precipitation - especially over the higher terrain is expected to linger into Monday - aided by the potential for a post frontal convergence zone as well as a weak upper level shortwave expected to clip the region. Snow levels will remain in 1500 to 2000 feet Monday, with storm total accumulations at the passes in the 4 to 6 in range from Sunday through Monday. Precipitation will taper off Monday evening with weak ridging is favored to briefly dry out conditions on Tuesday, with Tuesday morning looking to be the coldest of the week - some lowland locations especially away from the water will dip to near freezing.

Ensembles continue to show the potential for a second Pacific storm system to move into the region mid-week into the Thanksgiving holiday - bringing another round of widespread precipitation and breezy/gusty conditions. Snow levels at or near pass levels on Wednesday would leave the door open for potential snow accumulations and/or a wintery mix of precipitation, including a small chance of freezing rain. This has the potential to cause travel impacts especially for those traveling across the Cascades ahead of the holiday. Beyond this ensembles continue to highlight active and potentially impactful weather through the weekend, especially through the higher terrain.

AVIATION

The Pac NW is under westerly flow tonight a system stalls over southern British Columbia. Scattered showers will mostly affect the coast, strait and north interior. The low level air mass remains moist with FEW-SCT layer around 1500-3000 ft, with BKC-OVC mid and high clouds aloft. Expect MVFR conditions early Saturday morning that may persist through much of the day. Rain increases in coverage Saturday night as this system over B.C. shifts south into western WA. 33

KSEA...VFR tonight with S winds to 10 kt. Lowering clouds and MVFR cigs by 12-15z which will persist through much of Saturday. 33

MARINE

Seas remain elevated, 10-13 ft, and a Small Craft Advisory remains in effect for the Coastal Waters and West Entrance through Saturday (and possibly into Sunday too). Winds through Saturday will generally range in 10-15 kt with a few gusts to 20 kt in the Northern Inland Waters. Winds will flip to W-SW on Sunday as a front tracks through. Expect strong winds through the Strait of Juan de Fuca with gales possible. Onshore flow prevails early next week with high pressure offshore. Winds will turn offshore again by Tuesday as the next systems approaches from the west. 33

HYDROLOGY

A weather system will move across western Washington late Saturday into Monday for lowland rain and mountain snowfall. No river flooding is expected during this period, but rivers will rise. The potential exists for additional, heavier precipitation during the middle of next week. However, uncertainty exists in both the location and duration of precipitation. River levels will continue to be monitored during this mid to late week period.

JD

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 4 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- West Entrance U.S. Waters Strait Of Juan De Fuca.