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Enjoy What’s Left Of The Nice Autumn Weather; ’Atmospheric Switch’ Is On The Way

Tim Durkan Photography

Enjoy the, mild fall weather this weekend, says KPLU weather expert Cliff Mass, because there is going to be a big shift to wetter and cooler weather in the days ahead.

“You can expect the precipitation to turn on in a big way during the next week to two weeks,” Mass said, explaining that computer models show that the typical switch from sunny and warm autumn days, to damper and cooler weather is upon us.

He expects that transition sometime next week. So if you’re a hiker, Mass says this weekend is one you will want to enjoy.

Enjoy The Nice Weather While It Lasts

“This weekend is the weekend to do it,” Mass said—especially Saturday.

“Sunday will probably be okay if you go north–you know, like Mt. Baker or something. But it is definitely going to decline after that. So the hiking season’s going to fade back after this weekend,” he said.

Mass says expect clouds Friday as a system approaches, with the possibility of sun as the afternoon progresses.

“It should be basically dry and temperatures getting up into the low 60s. So, not a bad day,” Mass said.   

Saturday will be “a really decent day,” Mass said, with temperatures likely climbing into the low 60s. “Maybe a little bit of low clouds in the morning, some fog,” he said, adding that the fog should burn off as temperatures rise.

A New System Moves In

On Sunday, a new weather system will be approaching, says Mass.  

“We’ll start seeing rain on the coast, earlier in the day. But most of the rain will go south of Seattle,” he said.  So, expect rain if you’re going to go to Portland or to the Oregon coast.

Mass says the rain line will be somewhere in Seattle or in the Puget Sound region.  

“So going downhill on Sunday a bit, but not too bad in the northern part of the state,” he said.

Next Week: Front Moves In Wednesday

Mass says there will be a break from the rain on Monday and Tuesday, when a weak ridge will pop up and keep us dry, holding temperatures again up at about 60 degrees. But then he says the real fall weather moves in on Wednesday, when a stronger frontal system will come in, bringing rain with it.  

“Then, we’re going to be starting the rain season,” Mass said.  “So, we’re going to be start having this on-and-off rain—and the systems will get progressively stronger.”

Mass says this transition from glorious fall to the long slog of wet and damp days ahead is “one of the the most amazing aspects of the climatology of our region.”

“Not every place has this kind of sudden turn-on and it looks like the computer models are suggesting that during the next week, week and a half, we’re going to make the transition, ” Mass said.

In this week’s podcast, Mass comments on the warmer than normal October we have had this year. He also explains how the strong El Niño system that is setting up will affect our weather this winter.

You can hear the whole conversation by clicking on the “play” icon at the top of this post.

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.

Bellamy Pailthorp covers the environment for KNKX with an emphasis on climate justice, human health and food sovereignty. She enjoys reporting about how we will power our future while maintaining healthy cultures and livable cities. Story tips can be sent to bpailthorp@knkx.org.