Flip the switch: Western Canada warms up as polar vortex shifts east

Nathan Howes and Jessie UppalDigital Reporter and Meteorologist

The coldest air of the season targets Ontario, Quebec and parts of Atlantic Canada early this week. Meanwhile, Western Canada finally breaks free from the extreme cold in this pattern reversal.

Call it a switcheroo: A complete pattern reversal is taking shape across the country this week.

The result will see a welcome warm-up in Western Canada while the frigid Arctic air pushes into the East with some of the region's coldest temperatures of the season to date.

SEE ALSO: January promises nationwide 'pattern shakeup'

Other than that, the national weather pattern takes a breather for several days this week. It will be relatively quiet for much of the country other than a potent atmospheric river set to bring multiple rounds of heavy rain and a high flood risk for the B.C. South Coast and parts of Ontario are seeing an extended period of lake-effect snow squalls.

We have a breakdown on the national pattern switch that will see temperatures flip-flop in the coming days, below.

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COLD LOOSENS GRIP ON WEST, WARMER AIR FILTERS IN

After several weeks of bitter cold in Western Canada, a pattern that refused to budge, relief is finally in sight for the region. Thanks to a solid state of La Niña, the West has been battling both frigid air, record-breaking cold at times, along with a much wetter pattern.

The upper atmospheric pattern breaks down this week as freezing levels rise, allowing for periods of rain to develop and impact B.C. instead of low-elevation snow.

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Just to give you an idea of how long the cold has persisted for, the city of Edmonton, Alta., hasn't see an above-freezing day since Dec. 11, 2021. In other words: It's been more than a month since Edmonton has been reporting below-freezing temperatures.

Extreme cold warnings have blanketed the Prairies for weeks. However, these alerts, as well as bitter wind chills, will come to an end as mild Pacific air floods the region.

Strong, warm downsloping winds in Alberta will also help bump temperatures several degrees -- even above seasonal across the region. We might even be able to climb to double digits in southern Alberta early this week.

Meanwhile, Saskatchewan and Manitoba will see quite the significant jump in daytime highs on Tuesday, with Winnipeg, Man., seeing a whopping 25-degree rise.

THE EAST'S TURN TO TAKE THE BRUNT OF THE ARCTIC CHILL

When we take a look at Central and Eastern Canada, there has truly been a lack of winter weather and Arctic air across this part of the country -- as predicted with this pattern in place.

However, the lobe of extremely cold air that kept Western Canada under a deep freeze will migrate and expand east -- entering Ontario, Quebec and the Atlantic provinces this week.

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The coldest air of the season makes a trip down south in Ontario and Quebec Monday overnight. In Ontario, lows are set to approach -20°C, dipping well into the -20s for areas north and east of the Greater Toronto Area (GTA). This would actually be the first -20°C temperature in almost two years for the city of Toronto. Feb. 14, 2020 was the last time the city reached a low of -20.6°C.

To complicate the cold setup in Ontario, strong winds off the warm waters of the Great Lakes set off snow squalls near Lake Huron and Georgian Bay Monday. Travel was certainly hampered in many locales near Lake Huron and Georgian Bay, with at least one accident reported southbound on the Highway 400 in the evening. Snow squalls will slowly taper off to flurries Tuesday morning as the winds diminish and shift directions.

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Looking farther east, Tuesday night looks to be the coldest for the Atlantic region, especially in the Maritimes. New Brunswick is likely to see overnight lows plummet into the -30s, while Nova Scotia can expect to see minus teens and -20s across the board.

The good news for the East, unlike what the West experienced recently, the cold spell will be short-lived as temperatures rise back up to above freezing in many areas by Wednesday.

LOOK AHEAD TO LATE JANUARY

Colder weather is expected to return from the Rockies to Quebec for the third week of January but the Prairies will not be as cold as they have been over the past several weeks, and the focus of the cold will be farther east.

That means B.C. should escape severe cold, and Ontario and Quebec should see consistent temperatures that are near seasonal for January instead of the roller-coaster that has dominated the fast couple weeks.

With files from Doug Gillham.