The weekend forecast is more complex than usual, thanks to something called a dirty ridge moving in, says KPLU weather expert Cliff Mass.
Sunny Friday Before Dirty Ridge Moves In
Friday will be a "very, very nice day" with sun and temperatures reaching the lower 70s, thanks to a ridge of high pressure in the skies above.
“A perfect fall day – well above normal," Mass said.
But he says on Saturday, something called a dirty ridge is expected to move in, bringing dueling weather regimes with it. A dirty ridge is an area of high pressure that’s not strong enough to push out all the clouds and rain. As a result, it will allow two weather regimes to settle in over the region.
“On the northern part of the ridge it tends to be cloudy, with maybe a few sprinkles. But as you go further south, usually it gets much sunnier and much, much warmer. And that’s what we’ll see this weekend,” Mass said.
Clouds To The North, Sun To The South And East
Those in Bellingham or headed north into British Columbia should expect cloudy skies, says Mass.
“And the further north you go, the better chance it will be to have rain,” Mass said, adding that will also be true for the Northwest coast around Tatoosh and beyond.
“Then if you go south, somewhere around Seattle to Olympia, you’ll break out of any clouds and it’ll get warm and sunny,” Mass said. “Over Portland and the Willamette Valley, it’ll be in the 80s. So, very different weather."
Meanwhile, eastern Washington will be warm and getting up into the 80s.
“If you want sun, you want warmth, just head south or head east and you’ll have it,” he said.
Dirty Ridge To Weaken Sunday
Fortunately, Mass says, the dirty ridge will weaken on Sunday as it builds northward.
“And I expect sun over virtually the whole region — everywhere in the northwest, even into Vancouver, temperatures getting up into the lower 70s,” he said, adding there may be some clouds on the coast, particularly on the northwest side of the Olympics.
But Monday and Tuesday, he says that dirty ridge will develop again, with clouds pushing south.
“But I don’t think we’ll see much (of that) south of roughly Everett,” he said. “So there will be sun on Monday and temperatures getting into the very low 70s from Seattle southward, and maybe the upper 60s around Bellingham.”
“So, not a bad situation,” Mass said. But if you’re chasing sunshine, you may need to hit the road to find it.
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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.
