Canadians may want to dig out their winter jackets early this year. Temperatures across much of the country are trending below seasonal averages, marking what could be one of the colder Novembers in recent memory, according to CTV’s Your Morning meteorologist Kelsey McEwen. She says a large upper trough - a dip in the jet stream high in the atmosphere - is setting the stage for a deep freeze. “There’s an upper trough where planes fly and that trough means an area of lower pressure that allows our jet stream to basically slide down the Gulf of Mexico,” McEwen told CTVNews.ca in an interview. “When that happens, the jet stream acts as a barrier between warm air to the south and cold air to the north, allowing all this cold air to push southward,” she added. The set up is creating a perfect recipe for a widespread cold outbreak. On the surface, a strong cold front is reinforcing the chill, ushering in Arctic air from northern Canada. “When you get these two things happening in combination - especially in November - you really get these cold, cold blasts of air,” she explained. By the weekend, much of southern and central Canada will be feeling the chill. Daytime highs in Manitoba are expected to dip below freezing as early as Saturday. Ontario-based cities like Toronto, London and Windsor may also see their first snowflakes of the season late Saturday into early Sunday. “Toronto’s daytime high on Sunday will be around 3 degrees Celsius compared to an average of 9,” McEwen said. “That is about 5 to 7 degrees below seasonal across many cities.” The upper trough, which stretches from southern Manitoba down to the Gulf of Mexico and back up to the U.S. east coast, is pulling a vast “U-shaped” pocket of cold air across the continent. This modified Arctic air mass is responsible for the sudden plunge, part of a natural swing between mild and frigid Novembers. What makes this week stand out? McEwen said this week has been “unique” with the large-scale movements of air we’ve had. “We’ve had the weather bomb and the nor’easter off the Atlantic coast, a system over Ontario and Quebec today and a pacific frontal system or Alberta clipper moving in over the next few days”, she said. “It’s like a kick-off to winter - we’re diving in with both feet instead of easing in. We’re getting the full meal deal preview of what winter could be.”
