What Canadians need to know about big changes in weather this weekend

B.C. is expecting its first 'significant atmospheric river' as residents in the Northwest Territories and Nunavut may face their first blizzard of the season

Published Oct 18, 2024  •  3 minute read

Heavy rainfall in Vancouver prompted the deployment of umbrellas for anyone who had to go outside last October. This October is no different, with heavy rainfall expected. Photo by Jason Payne /PNG

This weekend, Canadians should expect big changes in weather — like the season’s first blizzard — as La Nina returns with the possibility of affecting the upcoming winter.

La Nina is a term referring to unusually cold ocean temperatures in the Equatorial Pacific, per the National Oceanic and Atmospheric Administration (NOAA).

“These cold waters in the Pacific push the jet stream northward. This tends to lead to drought in the southern U.S. and heavy rains and flooding in the Pacific Northwest and Canada,” according to NOAA. “During a La Nina year, winter temperatures are warmer than normal in the South and cooler than normal in the North.”

La Nina is expected to develop over the next couple of months, said Weather Network meteorologist Melinda Singh.

It’s a possibility that most of Eastern Canada will see above seasonal conditions, she said in a video posted to X on Thursday night, while B.C. and the Prairies may see below seasonal conditions.

“But if the coldest air is located in the eastern Pacific, then over 80 per cent of the country could see below seasonal conditions this winter season,” she said.

However, this returning La Nina will be “weak and short-lived” and neutral conditions may return in time for spring, said Singh.

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Meanwhile, this weekend, Canadians in the two northern provinces could experience the first blizzard of the season, with heavy snow and strong winds, per the Weather Network.

As of Friday morning, Environment Canada has issued snowfall warnings in parts of the Northwest Territories, as well as wind and blizzard warning for parts of Nunavut. Some areas in Nunavut were also placed under a winter storm watch.

To the west, B.C. is expecting its first “significant atmospheric river — described as long, narrow regions in the atmosphere, like rivers in the sky, that transport most of the water vapour outside of the tropics, according to NOAA.

The atmospheric river is “set to bring over 100 mm of rainfall to the South Coast and lower mainland over the weekend,” the network said. Densely populated areas in B.C. will be targeted and localized flooding is likely in certain areas.

The rainfall could turn to snowfall for some residents living in higher elevations, the network said.

“Freezing levels are expected to climb from 1,500 metres on Friday to 2,200 metres on Saturday. With the help from the atmospheric river and some Arctic air sinking southward, folks above these elevations along the coastal and interior mountains could see a hefty helping of snow,” the network explained.

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In the Prairies, drastic changes are expected as Arctic air cools the region. Temperatures are expected to drop, going “from the upper teens to low single-digit temperatures by Monday,” per the network, adding that Calgary and Edmonton may see a “snow risk” in the forecast as early as next week.

“The weekend cooldown will be even more drastic in Saskatchewan and Manitoba, where highs in the low 20s will quickly fall to below ten degrees on Monday and Tuesday,” the network said.

While Canadians in Southern Ontario have already seen some light snow overnight on Tuesday, going into the weekend there will be milder temperatures. Eastern Canada will also get a break from winter weather this weekend as sunshine and light winds are expected to last into next week.

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