Weathercatch: From 60 to snow – why here and not Pennsylvania?

It was a lovely start to November. Temperatures in the 50s to low 60s made winter seem far away, despite the waning daylight.

The remarkably mild weather that kicked off the month wasn’t isolated to our region, but extended all the way from the Pacific Northwest to Pennsylvania. On Nov. 4, temperatures climbed to 60 degrees in Spokane, 72 in Minneapolis and 66 in Philadelphia.

Then the weekend arrived and the nation’s weather went into seesaw mode. Springlike weather intensified in the central and eastern U.S. at the same time that an arctic chill descended over the Pacific Northwest.

By Sunday, we were in the grip of a blast of cold air and an accompanying snowfall – ranging from flurries in Spokane and up to 2 inches on the Palouse to heavier accumulations in the mountain passes. Slick driving conditions led to several traffic accidents in the Inland Northwest that morning, including the jack-knifing of a semitruck that blocked U.S. Highway 195 near Pullman.

The wintry chill pushed into this week, delivering colder temperatures and more rounds of snow. A system that moved in Monday night delivered widespread snow to our region overnight and into Tuesday. What’s more, another series of winterlike storm systems are predicted to arrive Thursday night through Sunday, bringing snow and a mix of rain and snow.

Remember on Sunday of last weekend, when temperatures crested in the 30s and many of our roadways were covered with slippery snow? On that same date, the mercury reached 75 degrees in Philadelphia and 73 in New York City. It also marked the fifth consecutive day of 70-degree or higher weather in Chicago.

Only a few days earlier, almost the entire nation was benefiting from an expansive dome of mild high pressure. Why did our region’s weather nosedive while much of the country remained locked in springlike conditions?

A southward flow of frigid air from Canada into the Pacific Northwest was able to scour out the abnormally warm temperatures and usher in the wintry conditions. As of now, it looks to be the dominant pattern over our region.

In other words, it’s highly unlikely we’ll see another 60-degree day in 2020.

What we’re experiencing is characteristic of the La Niña pattern that’s intensifying in the tropical Pacific Ocean. La Niña episodes tend to cause colder and stormier conditions in the Pacific Northwest and northern Plains, compared with milder conditions in other parts of the country.

Temperatures are expected to run about 5-10 degrees warmer this weekend, which could bring our region snow mixed with rain or snow that turns into rain. Higher elevations should see a generous dose of snow.