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Mass On Friday Snow Forecast: Latest Models Show 'This Front Is Coming'

It’s not always easy to predict lowland snow in the Pacific Northwest, but the latest weather models confirm snow is coming on Friday, says KPLU weather expert Cliff Mass.

What’s Certain: Snow Is Coming

“Timing might shift a few hours either way, but folks, this front is coming,” said Mass, who teaches atmospheric sciences at the University of Washington, on his weather blog. “There is great confidence in this forecast.”

Snow will begin falling in western Washington late Thursday or early Friday — earlier and heavier than previously predicted, said Mass. And what starts as a light dusting in the lowlands will turn into heavier precipitation by the Friday morning commute, particularly in the east Sound area, he said.

What’s Not Certain: How Much Snow Will Fall

By the time snow turns into rain around 1 p.m. Friday, Seattle will have seen 1 to 3 inches of snow. Parts of King and Snohomish counties will have seen more snow while areas south of Tacoma and over Port Angeles will have seen less.

“There are considerable uncertainties in the amounts, which could easily be different by 50 percent over the lowlands than shown above,” said Mass, adding the probability of snow itself remains very high.

"So be prepared, such as working from home or staging your car at the bottom of a hill," he said.

The National Weather Service has issued a winter weather advisory, effective from 1 a.m. to 1 p.m. Friday. The warning is issued when 1 to 3 inches of lowland snow is likely. 


The weekly KPLU feature "Weather with Cliff Mass" airs every Friday at 9 a.m. immediately following BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KPLU Environment Reporter Bellamy Pailthorp. Cliff Mass is a University of Washington Professor of Atmospheric Sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to a podcast of “Weather with Cliff Mass”shows.