Thursday and Friday brought exceptionally warm weather and sunny skies to many places around the Northwest. But they won’t last through the weekend, says knkx weather expert Cliff Mass.
On Thursday, temperatures reached the mid-60s throughout much of Puget Sound.
“Pretty warm,” Mass said of the abnormal pattern. “September temperatures, not November temperatures.”
He says Friday will be another very warm day.
“I expect Seattle to get to 63-65; lots of sun during the morning and maybe just some high clouds during the afternoon,” he said.
Why So Warm?
Mass says during the last few weeks, low temperatures have been 3-5 degrees above normal, with some days spiking into the 60s.
Mass says, interestingly, the same dynamics that have produced much of the extraordinarily wet weather that helped push this October into record wet territory over the past few weeks is also the reason for the warmth.
“We’ve had this persistent circulation pattern, in which we’ve had low pressure off shore and high pressure inland,” Mass said.
The low pressure can, and often does, bring rain in, he says.
“But it also sweeps up warm air from back down in the sub-tropics and the tropics and it draws that warmth into us. And there’s enough sun that gets in and the temperatures surge,” Mass explains.
But that all changes on Saturday, with the arrival of a fairly strong front of wet weather on Friday night.
“In fact, this is what we call ‘an atmospheric river,’ with lots of moisture behind it,” Mass said, “It’s going to invade our region,” he said, “so expect it to be a pretty wet day tomorrow.”
He says the mountains could get 1-3 inches of precipitation and there could be as much as a half an inch in the lower elevations around the Puget Sound region, with temperatures dropping to somewhere between 55 and 57 degrees.
“Not so great,” Mass said of Saturday.
“Sunday looks like the better day,” he said, as that front of wet weather moves through, with just a few showers expected in the mountains and possible showers in the lowlands around Puget Sound. It will be cooler though.
“It’s going to open up sometime in the afternoon, but temperatures only getting up to the mid-50s – maybe upper 50s – so, a knock down,” Mass said.
Rainy Next Week
Next week, Mass says expect rain showers coming in and out, but it’s hard to say right now how much and where.
“It really depends exactly where the fronts are. It’s going to rain a lot on the coast and offshore. And how much gets inland is a little unsure right now,” he said.
To hear the forecast and discussion of the snow outlook for this winter in the Northwest, you can click on the “play” icon at the top of this post.
The weekly knkx 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 knkx 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.