Here's how — and why — Alberta's big temperature swing is happening

Alberta is experiencing a little case of winter weather whiplash this week and competing air masses are to blame.

The temperature in Edmonton dropped to a frigid – 25 C on Sunday accompanied by a light dusting of snow. By Thursday, the city can expect a high of 7 C with a 40 per cent chance of rain showers in the forecast.

But why and how does this happen?

This part of the country often finds itself competing between two different air masses, said Environment and Climate Change Canada meteorologist Justin Shelley. 

"The Arctic air mass, which we had in place for most of last week, often will sort of entrench itself over the Prairie provinces and … back itself up against the Rockies and just remain in place until something can move that out," Shelley said in an interview with CBC News on Monday. 

"And usually what that is, is an upper ridge of high pressure with a change in direction of the winds."

A west-southwest flow across the Rockies brings a warming and drying wind, Shelley said. After a brief dip below freezing on Wednesday, Edmonton will be in plus territory again by Thursday. 

Shelley said chinooks will impact the Edmonton region about 10 to 15 times a year in the winter months whereas in Calgary, that number is closer to 20 or 30. 

Temperatures above zero are actually not that uncommon in December, Shelley said.

"Our normal daytime high right now for the beginning of December is about a high of –4 C, but overall in December as a whole, we typically see about 10 days where the average temperature is above freezing," he said. 

"A lot of that owes to these warm southwest-westerly winds kicking in."

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The big swing to warmer temperatures brings with it a risk of freezing rain, something Shelley said to watch out for if you're commuting. 

Shawn Coffill, an owner of Outdoor Ice Inc., said his work of building and maintaining ice rinks has already been a bit of a roller-coaster. The early cold helped, but then the heavy snowfall did not. 

"We've got a good start this year, other than the warm weather coming up, it's pretty good so far," he said in an interview Sunday. 

Coffill's company maintains 19 rinks and skate trails — equalling more than 28,000 square metres of ice. 

The coming warmth is not ideal for making ice. Coffill said the ideal ice-making temperature is –10 C or –15 C because the water doesn't freeze too quickly and you can do multiple layers at once. 

Though it may put a snag in his plans, Coffill said there's always other work to do. 

"I text my partner and say, 'Oh man, did you see the weather?' and they were like, 'Oh, what do we do?'"

"We just plan other things, like if we have stuff on the back burner, we do that. We don't generally flood when it's warm because you'll actually take ice away."