Outages, delays likely as major winter storm hits Ontario
Hazards will transition over to powerful winds and snow squalls by Monday
Major impacts are likely across Ontario as another powerful low-pressure system traverses the province with an entire assortment of hazardous conditions.
A blizzard is underway in northeastern Ontario. Significant amounts of freezing rain will persist into Sunday night in cottage country and eastern Ontario. Heavy rain and thunderstorms in southwestern Ontario may lead to flooding.
The threats don’t end there. Powerful winds and dangerous snow squalls will build into the region heading into the day on Monday, threatening power outages and road closures.
SEE ALSO: The polar vortex is on the move! Canada's winter forecast update
Freezing rain continues in eastern Ontario
Warm air aloft provided plenty of freezing rain to southern and eastern Ontario through the day Sunday, coating surfaces, trees, and power lines with a weighty crust of ice.
While precipitation will transition over to plain old rain in southwestern Ontario, we can expect the icing threat to continue across eastern Ontario through the overnight hours Sunday into early Monday.
In addition to the slippery conditions this will create, winds are also forecast to pick up, which increases the risk of power outages as the ice builds up on trees and power lines.
Blizzard risk builds in the northeast
Strong winds and heavy snow over northeastern Ontario are forecast to bring whiteout conditions across the region into Monday morning. Areas east of Lake Superior are also at risk of seeing blizzard conditions, making highway travel downright dangerous, especially around Wawa, Chapleau, and Timmins.
Areas hardest hit by the heavy snow could see up to 30-50+ cm by the time the storm passes. Folks should expect some road and highway closures.
DON'T MISS: Your winter storm preparation checklist
Those near and south of Sault Ste. Marie are forecast to see a bit of a wintry mix in addition to the heavy snow, impacting travel along Highway 1 toward Sudbury and North Bay.
Heavy rains threaten flooding in southern Ontario
Warmer temperatures over southern Ontario paired with the high atmospheric moisture brought heavy late-December rains to the region late Sunday.
While monthly rainfall averages across the south in December stay around 40-50 mm, we could see 50+ mm of rain locally north of Lake Erie, including the Grand River watershed, in a 12-hour period.
However, due to recent cold temperatures, the ground across much of the region is frozen, which will significantly limit the amount of rainfall absorbed into the ground and increase the risk of flooding.
Along the Humber River watershed, we're looking at the threat of ice jams due to repeated freeze-thaw cycles, increasing the risk of damaging floods.
Thunderstorms are also possible in southwestern Ontario as some instability inches into the region late Sunday through the pre-dawn hours Monday.
Damaging winds, flash freeze risk builds Monday and Tuesday
After Sunday night's rainfall across southern Ontario, we will see a rush of cold air move into the region on Monday. Communities in and around Hamilton and Niagara could see temperatures drop by as much as 10°C in just one to two hours.
This is a red flag signalling the risk of a flash freeze late Monday morning as the ponding water on the ground suddenly freezes up and forms a layer of slick ice.
RELATED: Winter storm aftermath: How to prevent ice dams and roof leaks
As the low lifts over Georgian Bay on Monday, we'll also see winds begin to pick up to damaging levels along the Great Lake shorelines.
Winds are forecast to blow southwest over Lake Erie, gusting between 80-110+ km/h. The Niagara region will bear the brunt of this wind before it shifts to the northwest later in the day.
By late Monday, we'll see the winds gusting northwest off of Lake Huron and Georgian Bay, with peak gusts between 70-100 km/h.
The damaging winds will also persist on Lakes Erie and Ontario, as well as throughout Prince Edward County, despite the shift in direction.
Folks should be prepared for some power outages with these winds, as they could knock down tree limbs and damage power lines.
Waves could reach up to 5 metres on the lakes as well, with 6-8 metre waves possible on southern Lake Superior. Folks along the shores should keep an eye out for sudden ice shoves.
The winds will continue through the night and into Tuesday. As temperatures continue to drop across southern Ontario overnight, lake-effect snow squalls could create whiteout conditions throughout the snowbelt regions.
As the gusty winds linger through Tuesday, we could see blowing snow continue to bring hazardous conditions for folks travelling to celebrate the New Year.
Stay with The Weather Network for more information and updates on this developing storm in Ontario.