Swath of snow, plunging temperatures, prolonged lake-effect all target Ontario

Digital Writers
·4 min read
Swath of snow, plunging temperatures, prolonged lake-effect all target Ontario
Swath of snow, plunging temperatures, prolonged lake-effect all target Ontario

Forecasters are keeping a close eye on the next weather-maker for Ontario -- another Colorado low -- threatening to bring snow and rain Thursday and Friday, depending on location. Snowfall totals will be highest north of the Nickel Belt, but 5-10 cm is expected for much of southern and eastern Ontario, with lesser amounts for much of the Greater Toronto Area, south of the 401. Along with the low will come a short-lived bump in temperatures in southern Ontario Friday, changing precipitation to rain, but will then take a nosedive by Saturday as Arctic air returns, leading to the coldest air of the winter thus far for next week, thanks to the Polar Vortex. For a closer look at what's to come, see below.


  • Colorado low to bring next shot of snow to Ontario Thursday

  • Snow will change to rain in the south Friday as milder air bumps temperatures

  • Shot of Arctic air will send temperatures plunging on the weekend, polar vortex to bring coldest air of the season so far next week


The upper trough responsible for the significant snowfall in California, as well as the warmth in Alberta, will begin to shift over the Rockies. At the northern edge, a cold front extending southward from the Canadian Prairies to the southern U.S. Plains will spark the Colorado low Wednesday night.

The resilient protective ridge situated over the Great Lakes will dissolve, allowing the storm to take its preferred track toward Lake Superior.

While northwestern Ontario will see snow filter in from the Colorado low Thursday morning, most of the day in the south will be dry, featuring partly sunny skies and mild temperatures.

ONSouthSnow (4)
ONSouthSnow (4)

The lingering Arctic air ahead of the low will likely result in snow for the lower Great Lakes, beginning Thursday afternoon and evening. The heaviest snow looks to remain north of the Nickel Belt.

Most of southern and eastern Ontario will see 5-10 cm of snow, but lower totals are expected south of the 401 corridor, where the snow will change to rain before ending, 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 and 5-10 cm north of the corridor.

Snow will then transition to rain along the 401 corridor Friday as milder air surges in, bumping temperatures to near or above freezing in most areas. However, winds will become gusty and temperatures will quickly tumble through the day as the system departs.

ONTempFri (TuesPM)
ONTempFri (TuesPM)

Turning north over the Great Lakes, the storm will then head to Hudson Bay, where it will linger through the weekend.


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. Temperatures will then gradually drop over the Great Lakes for next week. A lack of ice on the lakes will act as a moderating mechanism for southern Ontario.


This will be a setup where Windsor will be colder than the GTA. The coldest air will detour around the Great Lakes, heading south of Lake Michigan and entering southwestern Ontario from the West. This occurs while the air targeting the GTA will be moderated by a lengthy trek over Lake Superior and Lake Huron. Look for a significant jump in ice coverage by mid-February.

Temperatures will slowly recover late-week, but 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 behind the system could produce dangerous travel with whiteout conditions.

Meanwhile, a prolonged period of lake-effect snow squalls is expected into next week, possibly continuing until next Friday, for the traditional snowbelt areas east and southeast of the Great Lakes. While the bands will meander across the snowbelts with changing wind directions, the snow totals for parts of the region will be most impressive.

Be sure to check back as we continue to update the forecast in Ontario.