Ontario walloped by intense snow squalls, impressive totals piling up

Powerful snow squalls could produce up to or more than 100 cm of snow across parts of Ontario through this weekend.

Road closures are possible as steep accumulations and near-whiteout conditions occur beneath the heavier bands of snow that roll inland off the lakes. Snow squalls can produce a rapid change in conditions over short distances.

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These potent bands of lake-effect snow will continue through Sunday, with some communities such as Gravenhurst in line to potentially see up to or more than 100 cm of snow by the time it ends. Hardest-hit communities could still see an additional 30-50+ cm of snow. As a reminder, lake-effect snowfall is a highly localized, high-impact weather event.

Prepare for challenging driving conditions over the next couple of days. Keep an eye on the radar through the weekend and keep up-to-date with the latest highway conditions before you head out.

Snow squalls continue this weekend

Chilly air pouring over the Great Lakes for the past few days has given rise to multiple potent snow squalls throughout the region. Bracebridge, Ont., reported 55 cm of snow through Friday evening.

Cold air is a key ingredient in lake-effect snow production. A strong temperature gradient between the frigid air above and the warm waters below creates convection, resulting in bands of lake-effect snow. Thundersnow is also possible in some of the heaviest snow squalls.

Our multi-day event began on Thursday and it’s expected to continue straight through Sunday.

Environment and Climate Change Canada has issued snow squall warnings for these areas ahead of the event.

Heavy snowfall rates of 5-10 cm an hour are possible especially through Sunday morning.

"Road closures are possible, especially over areas that receive multiple snow squall bands," the agency warns. "Prepare for quickly changing and deteriorating travel conditions."

We’ll watch persistent squalls meander a bit as they target communities from Kincardine to Dundalk and from Parry Sound to Barrie. Snowfall rates of 5-10 cm/h are possible, especially through Sunday morning. We could also see some thundersnow in this area.

Forecasters will closely monitor a snow squall off Lake Erie, which could impact Buffalo to Fort Erie if it moves slightly north on Saturday or Sunday.

Another snow squall blowing off Lake Ontario will bring 120+ cm to parts of northern New York through this weekend. This squall could affect Kingston with 5-15 cm of snow if it moves slightly north this weekend.

Sault Ste. Marie will be caught beneath persistent rounds of strong squalls throughout the event into this weekend.

Folks across the Greater Toronto Area (GTA) should see little to no impacts until we get to Sunday, when shifting winds could bring flurries closer to the region.

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Winds shift Sunday night into Monday

Things could get more around the GTA by the end of the weekend as Sunday will bring a wind shift. We’ll see winds shift from a westerly direction to a more northwesterly orientation, shifting the location of the snow squalls accordingly.

The squall blowing off Georgian Bay will shift down through Barrie and set up over Collingwood and Angus. Meanwhile, the squall off Lake Huron will shift south along Highway 21 through Goderich and set up just south of there.

It’s after this shift that we could see a burst of flurries move into the GTA. The arrival of big-time snowfall totals is great news for Ontario's ski resorts, as early December will offer some of the best natural snow and snowmaking conditions we've seen in quite some time.

However, it does also mean trouble for the roads. Heavy localized snow with winds gusting between 40-60 km/h, will lead to whiteouts, slippery conditions, and difficult winter travel through this long duration and major lake-effect event.

Folks travelling along highways 21, 6 and 26 will be affected by the squalls blowing off Lake Huron.

Drivers heading out along highways 11, 400, 69 and 26 will see impacts from the squalls blowing off Georgian Bay.

Whiteouts, slippery conditions, and difficult travel will persist throughout the region for the duration of this lake-effect snow event. Remain alert for potential traffic jams, road closures, and impassable roads.

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