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Polar vortex plunges south, dangerously cold conditions coming to Canada

Wednesday, February 3rd 2021, 1:45 pm - A couple of low pressure systems will bring warm air up from the Gulf of Mexico while Arctic air rushes south towards Ontario.

Even though there has been such a scarcity of harsh winter weather in Canada, frigid air is getting ready to pulse south. A warm temperature anomaly will straddle the surging cold this weekend, creating a dynamic temperature profile featuring a 40°C temperature difference across Hudson Bay.

Two things will happen simultaneously in the atmosphere to create such a sharp temperature gradient over the world’s second-largest bay. By Friday, frigid air rushes south along a deep trough through Nunavut. A Greenland high-pressure system will then intensify and set the wheels in motion to draw up incredibly mild air along the backside of the polar vortex.

The forecast Colorado low will follow the upper-level flow northward. This wonky upside-down temperature pattern will then develop and send temperatures shooting towards the freezing mark in Coral Harbour, Nunavut, while communities further south shiver below -30°C.


The result? It's quite the unintuitive temperature map, with milder air north and frigid air south. The milder air will attempt to wrap around the backside of a low with massive temperature swings in the foreseeable future for parts of Nunavut along the western shores of Hudson Bay.

The source region of this mild air originates from the Gulf of Mexico, roughly 5,000 km away from Toronto, and is advected northward by a couple of low-pressure systems across Ontario and Atlantic Canada that will develop over the next several days.

The upper-level energy from the low helps further amplify the upper air pattern to create quite the temperature dichotomy swirling around Hudson Bay by this weekend.


What kind of upper-level pattern spawns such an unusual temperature pattern?

Both the trough and the ridge fall on the fringes of the climatology record, but the truly formidable outlier appears to be the Greenland block.

Think of the jet stream as a sophisticated system of atmospheric highways. A pronounced fork in the jet stream will develop by this weekend, so watch for the split-flow magic as air travels around a massive Greenland block, as this is the blocking pattern magic in action.


Will this create a famous Hudson Bay swirl? We're probably out of luck. As a rule, we need a cut-off, weakening low with a low-pressure signal near the same location as you head up in elevation. With a lack of pressure uniformity, it's unlikely we'll see the 'faux-hurricane' like witnessed back in last October.

The cold air will linger across Central Canada throughout February, with reinforcing shots of arctic air flowing readily out of the Canadian Arctic.

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