Sudden snow storm sets stage for unpredictable winter

Spokane set a new snowfall record, six days short of the official start of winter, when 7.1 inches of the white stuff fell on Dec. 15.

The storm forecast, which took most every expert by surprise, suggested the area would see about 1 inch. It surpassed the previous record for the date of 4.8 inches, set in 1963.

This early glimpse of winter is only a sample of what lies ahead as the Northwest faces a second consecutive La Nina winter.

Two months ago, retired Eastern Washington University geography professor and noted long-term weather forecaster Bob Quinn, predicted that our region's weather would be influenced by the colder than normal ocean temperatures in the northern Pacific Ocean.

"We still have a weak La Nina pattern, and the end result is it will play a modest role in organizing the winter weather patterns," Quinn said Dec. 13.

And while a La Nina means sea surface temperatures tend to be somewhat colder than the flip side - an El Nino - currently, the northern parts of the Pacific Ocean are slightly warmer.

"We will slowly but surely, eventually make average snowfall, which is 45 to 50 inches," Quinn said. So far, through Dec. 18, just over 15 inches of snow had fallen at the National Weather Service near Spokane International Airport.

Surprisingly, that included 7.2 inches in November which started strong and allowed some ski resorts to open earlier than they had in 20 years. Then came a warm up where much of that snow went away and kept hills from opening over the usual lucrative Thanksgiving holiday.

Ironically, however, snowpacks in many river basins on Dec. 1 in the Pacific Northwest were still substantially higher than in 2016.

"In the late fall this year we saw just enough storm activity with that warm water North Pacific," Quinn said. "When you do get storms, you're tapping into a lot of moisture."

Typical during a La Nina, a high-pressure ridge forms over the eastern Pacific which usually subjects the region to a northerly flow, Quinn explained.

But equally fickle, like the exactness of weather itself, over the past month instead of forming offshore, that ridge set up right on the coast - and partially over the Pacific Northwest.

"So the end result was our dry and fairly typical fog and low clouds kinda' stagnant pattern," Quinn said. That ridge began to retreat to its more usual location last week which ushered in Friday's storm.

"What that's going to do is let some colder air come down out of Canada, but it's also going to permit these storms from the Aleutians to drop down along the coast, and in some cases, sit there for a few days before they head down to Oregon and points further south," Quinn said.

Quinn was right, to a point, when he predicted the event being "Not 8–10 inches, but an inch and an inch and an inch." The ridge was predicted to extend further north this past week for a cold, dry, more northerly flow of air.

Officially, the end result fooled everyone, but considering the complex geography of the Pacific Northwest, climate curveballs are not uncommon.

The large-scale differences of regional topography make it a lot more difficult to forecast, Quinn explained. The wet west side clashes with the high elevations of the Cascade Mountains followed by the semi-arid region and then clash with the Rockies.

"As soon as you come across and get into the intermountain area, all things get much more difficult," Quinn said.

That strong and slightly mobile high-pressure ridge will continue to influence winter weather the next several weeks.

Quinn's guess is through early winter and the rest of December will keep going back and forth from cold and dry to periodic storms along the coast bringing us "Mostly snow." He predicts that overall it will be below normal precipitation through December and most of January.

"By the time you hit the end of January, into February, all bets are off," Quinn said. That's where traditionally another change begins to occur.

Paul Delaney can be reached at [email protected].