Bundle up and get ready for possible lowland snow in places. KNKX weather expert Cliff Mass says cool air moving in to western Washington will push temperatures below freezing in many lowland areas this weekend, with a chance of snow most likely on Sunday.
“Right now we have much cooler air over us,” Mass said on Friday morning.
“You may not have noticed it because of the clouds, but actually the atmosphere is progressively cooling down under northerly winds aloft.”
On Friday, he says temperatures will only reach the mid-40s at best and it will remain cloudy as a convergence zone weakens.
“So kind of a blah day, clouds will sort of dissipate later on,” Mass said.
Saturday morning it starts to get interesting, he says.
Below Freezing Saturday
“We’re going to have cold air over us, the clouds will have basically moved out. That’ll allow good radiational cooling into space and I expect the minima tomorrow (Saturday) to be some of the coolest we’ve seen in a while,” Mass said.
Many people will need to bundle up.
“A number of locations in the lowlands of western Washington will get into the 20s. And so there’ll be some frost and even some water could freeze. So, cooler than normal, certainly cooler than we’ve seen.”
He says Saturday will be sunny but still quite cold.
“Temperatures will only get into the mid-40s because the air’s so cool,” Mass said.
Lowland Snow Possible Sunday
Sunday brings more interesting weather, Mass says.
“We’re going to have fairly cold air in place and then an upper level trough is going to move toward us,” he said. “That’s going to bring clouds and a little bit of precipitation. And so the question is who’s going to get snow and who won’t?”
Mass says it will probably be warm enough that the precipitation will fall as rain in most places.
“And not very heavy rain. But once you get to 500 feet or above, the higher hills… the higher elevations in Snohomish or Whatcom counties, there could be a little bit of light snow mixed in there,” he said. “So, don’t be surprised about that.”
Double Check The Forecasts
Mass advises checking forecasts frequently, since this is the hardest kind of weather event to predict.
“If it was off just a little bit, things could be different,” he said.
Mass says the upper level trough will move past us toward the end of the weekend and we’ll return to fairly sunny conditions with temperatures reaching the mid-40s again and no snow.
“So, an interesting period; a little bit cooler than we’ve seen for a long time,” he said.
To hear the full conversation – including a discussion of how the La Niña pattern is influencing our winter weather in western Washington right now – you can click on the 'play' icon at the top of this post.
Weather with Cliff Mass airs at 9:02 a.m. Friday, right after 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 podcasts of Weather with Cliff Mass shows, via iTunes or Google Play.