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Ontario is bracing for a drastic change in winter weather this week, with forecasters warning of heavy snowfall across the north and lake effect storms across southern regions as November approaches.
What to Expect in Southern Ontario. Will GTA survive the snow?
While the center of the system will remain in the north, southern Ontario will not escape its reach.
By Thursday, the release of Arctic air will spread into the Great Lakes Basin, causing falling temperatures and gusty winds of 60-80 km/h. Those gusts are expected to push the lake-effect snowstorm into snowpack down to Lake Huron and Georgian Bay, with forecasters warning that the Greater Toronto Area (GTA) could also see heavy snowfall.
Travel may be hazardous through snow-covered areas Thursday and Friday, with whiteout conditions likely during storm activity.
The Toronto forecast points to a sharp drop in temperatures after rain in the middle of the week. This is because the polar vortex has started to wobble. Think of the polar vortex as a wall of strong winds that keeps cold air near the poles. It is located about 15-48 km above the ground above both the poles and is not a new thing. But when something happens to disrupt this “wall of wind”, the cold air sinks to the south.
Good old-fashioned winter weather depends on a weak or disrupted polar vortex. In this case, the disruption will be primarily caused by something called a “SSW” or “sudden stratospheric warming” that will weaken the “wind wall.” Although cold air circulation is not unusual at this time of year, the “SSW” phenomenon that causes it to occur early in the season at this time of year has occurred only a few times in the past 70 years.
The current La Nina is also playing a role in this change in cold weather. The CityNews Winter Outlook, released earlier this month, says the first half of winter in the Great Lakes will be cold, while the second half is expected to be mild beginning in 2026.
Toronto’s short term forecast
Monday will be mainly sunny, with a high near 9°C and temperatures falling to 4°C tonight.
On Tuesday, the day will be cloudy and rain will start in the afternoon, due to which the maximum temperature will reach 9 degrees Celsius. There is a possibility of rain at night with a minimum temperature of 7 degrees Celsius.
Wednesday will be cloudy throughout the day with intermittent rain, which will turn into rain/snow by the evening. Highs will begin to drop to 11°C in the afternoon as the gusty winds subside. Overnight, there is a 40 per cent chance of showers or thunderstorms, with temperatures falling to 0°C and strong winds continuing.
The city will remain cloudy on Thursday with occasional snowfall. Wind will also blow and the maximum temperature of the day will be 1°C. Heavy rain is expected overnight, with a low of -2°C and a wind chill near -10 by Saturday morning.
What will areas north of the GTA see?
A low pressure system developing south of Lake Superior late Tuesday is expected to merge with the Alberta Clipper, causing widespread snowfall through Thursday, creating hazardous travel conditions in northern Ontario. Environment Canada has issued winter storm watches for dozens of communities, including Thunder Bay, Timmins, Kapuskasing, Marathon and Wawa.
“The snow will also be accompanied by strong northerly winds, potentially resulting in blizzard conditions that may reduce visibility to near zero at times,” Environment Canada writes Monday. “Uncertainty remains regarding the exact track of the low pressure system and therefore the corridor of the heaviest snowfall. Total snowfall amounts could exceed 30 cm in some locations north of Lake Superior.”
Drivers are being urged to prepare for poor visibility, rough roads and possible closures.
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