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Triple winter threat takes direct aim at Ontario

Thursday, February 4th 2021, 6:30 pm - It may have taken until February, but winter is really starting to show its wrath across Ontario.

Winter's touch has been light so far in Ontario, with another shot of above-seasonal temperatures once again Thursday, but the season is once again set to show its true face. A Colorado low began moving into the province's southwest Thursday evening, and through Friday it will bring a widespread 5-10 cm for most people, higher for some of the snowbelts, and generally lower for the GTA. In its wake will be strong gusty winds ushering in a shot of bitter cold, followed by a prolonged period of lake-effect snow thanks to the wide-open lake waters from a mostly mild January. More on the timing and impacts of what's to come, below.


  • System continues overnight through Friday, exiting later in the day
  • Shot of Arctic air will send temperatures plunging on the weekend, polar vortex to bring coldest air of the season so far next week
  • Prolonged period of lake-effect snow ahead over the coming days


The snow with this system began in the southwest Thursday evening, and it will be relatively fast-moving, such that its heaviest snows will have fallen by dawn for most of the southwest and GTA, though eastern parts of the province will still be seeing the ongoing impacts through part of the day.


By the evening, much of southern and eastern Ontario will see a general 5-10 cm of snow, but sightly lower totals are expected south of the 401 corridor, where lingering warm temperatures may facilitate a brief switchover to rain, especially in the Niagara region.

A wide range in snow accumulations are anticipated for the GTA, depending on elevation and distance from Lake Ontario. Totals of 2-5 cm are possible south of the 401, with 5-10 cm expected north of the corridor. Initially higher totals up to and locally exceeding 15 cm were expected for parts of the Dundalk Highlands.

ON South Snow

The north, which will have seen the snow begin much earlier, will bear the bigger brunt of this system.

Some 20-30 cm is possible for parts of the region through Friday, particularly for areas north of Lake Superior, where some lake-effect enhancement is expected.

ON North Snow

Back in the south, the departing system will drag in very strong winds behind, ramping up through the morning and staying strong through the afternoon and evening.

The strongest winds will be across the Niagara region where wind gusts near 80 km/h are likely.

21-02-04 ON Wind

Aside from adding a harsher edge to the day's wind chill values as temperatures fall, blowing snow will be an issue, as will coastline flooding on the shores of Lake Erie, whipped up by the winds. A flood warning is in effect for part of the coast.


Beyond the storm, the most prominent lobe of the polar vortex this winter is expected to migrate over central Canada for the weekend and beyond.


"A blast of Arctic air is likely for next week with the coldest air of the season likely for Monday through Wednesday," says Weather Network meteorologist Dr. Doug Gillham. "Daytime temperatures will struggle to even reach -10°C, combined with a bitter wind chill."

Temperatures look to slowly recover late next week, but still remaining below seasonal.

As well, forecasters are closely watching a system that will develop along the Arctic cold front as it tracks into southern Ontario on Sunday. While the system doesn’t look impressive on computer models, it does have the potential to overachieve, as the snow will be very fluffy. Coupled with that, strong winds and plunging temperatures could produce dangerous travel with whiteout conditions.


Meanwhile, a prolonged period of lake-effect snow squalls is also expected to begin this weekend, possibly continuing until next Friday for the traditional snowbelt areas east and southeast of the Great Lakes.

A belt of warm air that filled most of Canada through the month of January has left the "cover" off of the Great Lakes basin, with the ice coverage still sitting well below normal. Now, as this blast of arctic air pushes across the open waters, the threat for impactful lake-effect snow squalls significantly increases.

EXPERT ANALYSIS: Why snow squalls are one of the hardest events to forecast

While the bands will meander across the snowbelts with changing wind directions, the snow totals for parts of the region will be substantial into next week.

"The way we see February tracking, the lake-effect bonanza and the battleground of air masses could bring some significant snow into the Lake Erie and Lake Ontario corridor," warns Weather Network meteorologist Tyler Hamilton. "Only time will tell."

Be sure to check back for the latest on the winter weather in Ontario.

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