In Skagit County, snow was reported falling as low as the 350-foot level in the town of Alger.
Snow showers also were reported falling as low as Denny Creek along Interstate 90, and numerous spinouts impeded traffic at Snoqualmie Pass.
As much as 12 inches of new snow is expected through Saturday night at Snoqualmie and Stevens passes, the National Weather Service reported. Traction tires are required for all vehicles in both passes.
In parts of Skagit, Snohomish and Island counties, heavy rain squalls formed in a Puget Sound convergence zone that could move south as the day progresses. Snow was reported at Lake Cavanaugh in Skagit County.
Gale warnings were posted in the Strait of Juan de Fuca.
Afternoon and evening thunderstorms are expected in the convergence Sunday as the cool weather pattern continues.
This is a developing news story. More information will be posted as it becomes available.