Arctic front approaching: When the wind blows, the temperatures will drop

The most unusual thing about the single-digit temperatures and double-digit winds headed for the Inland Northwest this week is how late in the season they’re finally arriving.

“It’s not out of the ordinary for our region to experience temperatures like this,” said Greg Koch, a National Weather Service meteorologist based in Spokane. “It happens most winters. But what makes it unusual this year is how unusually mild much of December and all of January was, as far as temperatures.”

Last month, Koch noted, was Spokane’s 16th warmest January on record – and those records go back into the early 1880s.

“To put it in perspective,” he continued, “so far the coldest temperature Spokane has had this season was 13 degrees back on Oct. 25. So Spokane airport has not had its temperature dip into single digits yet this winter. But it looks like a near certainty by the time we get to the second half of this week.”

Late Wednesday and into Thursday, Koch said, an arctic front will plunge into the region, bringing the mercury down to about 5 degrees and wind gusts of up to 35 mph. He expects the result to be windchill values as low as minus 10 on Thursday.

Koch said “those gusty northeast winds will likely persist throughout the day Thursday and into Friday,” while the bitter cold is expected to last through Saturday, when high temperatures will be in the teens and the lows in the single digits.

As for snow, Koch said it’s not entirely clear.

“We have some low chances of precipitation in the forecast Thursday,” he said, “but it doesn’t look like a big snow event will accompany this arctic event. But we will keep an eye on later into this week and early next week, because once we have this cold air in place, the arrival of moisture could bring snow with it.”

The change in weather in North Idaho and Eastern Washington, he said, is the result of a “glancing blow” from what is a “very large and expansive arctic air mass that’s going to plunge east of the Continental Divide,” making for “much colder in areas of Montana, the Dakotas and the central United States.”

While it has been a warmer winter than usual, Koch said the Inland Northwest has seen a pretty average amount of snow.

That’s true in the mountains, where snowpack is “pretty close to 100%” of average in northeast and north central Washington and between 90 and 100% in North Idaho. It’s also true in the valleys, where Spokane International Airport has received 38.3 inches of snow this year, compared to an average of 35.5 inches.

The difference, Koch pointed out, is that the warmer temperatures have melted that snow faster than usual, leading to less accumulation.

But that may change.

The outlook for the remainder of the winter calls for temperatures that are at or below normal and precipitation that is at or above normal. In addition, the snow-making tendencies of La Nina winters, such as this one, are normally felt more significantly in February and March than in November and December, Koch said.