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First rain then snow, seasons change in a hurry across southern Ontario

Thursday, November 11th 2021, 6:30 pm - A pattern change is underway in southern Ontario, with showers expected to linger into Friday, and cooler weekend ahead.

A pattern change is almost upon southern Ontario after some pleasant fall days. The far northwest is already in the midst of a potent winter blast, with some areas notching totals of 40-50 cm through Friday morning. The south isn't in for anything like that intense, but overnight showers will linger into Friday for parts of the region. Much colder weather this weekend could also result in bands of lake-effect snow, with locally heavy snow totals possible for the traditional snow belts. More on the timing of these systems and potential impacts, below.


Two low-pressure systems have joined forces to bring very heavy snow and strong winds to parts of the eastern Prairies, spreading across the border into northwestern Ontario as well.

Widespread snowfall and winter storm warnings were still in effect Thursday night as the heaviest snow was at its peak in the northwest, and a difficult situation awaits anyone who has to be on the roads Friday.

MUST SEE: Travel not recommended for parts of the Prairies, NW ON as potent storm hits

PR Snow

Travel along Highway 17 will be treacherous, as gusty northeasterly winds between 70-90 km/h will make for poor visibility and slippery road conditions, continuing through Friday afternoon. For areas near Lake Superior, heavy overnight rains will begin tapering to flurries Friday morning.

Southern Ontario on the other hand will see the tempered, but prolonged and varying effects of the system, beginning Thursday night and continuing through Saturday and Sunday, when lake-effect rain and snow develop once again.

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Rain was set to begin Thursday night from the eastern shores of Lake Superior, all the way through cottage country, the Greater Toronto Area and southwestern Ontario. By Friday morning, the leading edge of the rain reaches Ottawa, while the back edge is pulling out of the GTA.

Conditions will improve across much of southern Ontario on Friday, with a southerly flow allowing for double-digit highs near 12 or 13°C.

PHOTOS: Ontario basks in November patio weather as temperatures soar

"But this is when the transition begins," warns Nadine Powell, a meteorologist at The Weather Network. "This is a huge low-pressure system that will generate cooler westerly winds this weekend."

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Light rain is expected across southern Ontario and the GTA on Saturday, but as temperatures cool Saturday night into Sunday morning, higher terrain inland from Lake Huron and Georgian Bay can expect a wet snow mix.

A surface trough behind the departing low will bring light rain showers across much of southern and central Ontario Sunday afternoon, but by late day, a mix with wet snow is expected for parts of central Ontario and the higher terrain northwest of Toronto. Some accumulations are expected above the escarpment and away from the Great Lakes, though with little to no accumulation expected for the GTA.

Chilly, near seasonal, weather will continue into early next week, with temperatures set to rebound to above seasonal for a couple of days during the middle of the week before colder weather returns late in the week or weekend once again.

Be sure to check back for the latest updates on the changing pattern across Ontario.

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