With the first chance of major lowland snow in the forecast since last February’s big snowstorms, people all around the Puget Sound region on stocking up on supplies and getting their snow shovels ready.
But KNKX weather expert Cliff Mass says forecasting snow around sea level here is one of the biggest challenges forecasters face. And at this point, the only thing anyone’s really sure of is that it will soon get very cold.
“To get snow here you need cold and you need moisture. And it’s hard for us to have really cold air and moisture at the same time in Seattle,” says Mass, a professor of atmospheric sciences at the University of Washington. “We’re good for warm and moist. We can get cold and dry. But, to get them both coming together is extremely difficult.”
The cold will be arriving Sunday afternoon as a low-pressure system north of Seattle starts drawing cold Arctic air from northern British Columbia into the region, via the Fraser River Valley north of Bellingham.
“Temperatures are going to start plummeting late in the day on Sunday,” Mass says. “There’ll be snow up near Bellingham and the San Juans. It’ll probably be rain down here.”
After the system moves through, Mass says more Arctic air will surge in, pushing temperatures even lower on Monday and Tuesday. Mass says Tuesday will be the coldest day the region has seen since last February.
“Highs only getting into the upper 20s, lows in the lower 20s here in Seattle," he says. "Really cold.”
But will there be snow? Mass says a weather system will go south of the Puget Sound region on Tuesday, likely hitting Portland and maybe parts of Southwest Washington with the white stuff.
But he says the real chance for the greater Seattle area to get hit with snow will be on Wednesday and Thursday, when a strong low-pressure system will be coming off the Pacific Ocean.
The system will cause strong easterly winds, descending the Cascade Mountains. At the same time, snow will be hitting Portland and moving northward towards Puget Sound.
“And the question is: how much will get up to us,” Mass says. “Right now, it looks like we’ll get at least a few inches. If the low goes a little bit further north, we could get a half a foot or more.”
But at this point, it’s too early to say anything definitely. Mass says on Monday or Tuesday, forecasters should have a better grip on the midweek forecast and what people can really expect.