A widespread blast of Arctic air flooding into the Great Lakes region will put an end to the above seasonal temperatures while brining a healthy dose of snow to parts of northeastern Ontario and southern Quebec through Saturday. For some, this will be the first measurable snowfall of the season, so drivers are being urged to brace for deteriorating and quickly changing conditions. Although the precipitation will remain as rain for much of southern Ontario through Thursday, a dip in temperatures by Thursday night could see that rain transition over to wet snow by Friday morning. A shot of lake-effect snow is also forecast for the region, with the arrival of cooler temperatures and Friday's gusty northwest wind. More on the timing and impacts, below.
THURSDAY INTO SATURDAY: SYSTEM THREATENS 20+ CM OF SNOW OVER PORTIONS OF ONTARIO AND QUEBEC
Milder and above seasonal temperatures will hang on for one more day across southern Ontario on Thursday, which means precipitation will continuing as rain for much of the day. A widespread 5-15 mm is expected for most areas.
However, for areas further north, the system will manifest as at-times heavy snow, particularly in northeastern Ontario and northwestern Quebec, thanks to colder temperatures with the arrival of Arctic air.
A winter weather travel advisory is in effect for parts of northern Ontario, warning of icy road conditions as the temperatures begin to dip.
"Prepare for quickly changing and deteriorating travel conditions," warns Environment and Climate Change Canada in the statement. "Take extra care when walking or driving in affected areas. Slow down driving in slippery conditions."
By late Thursday night, southern Ontario and Quebec will see the rain from earlier in the day transition into mixing or wet snow, along with gusty winds. Eastern Ontario and into southern Quebec will see a cold rain transition to mixing and snow into Friday morning.
The combination of cooler temperatures and Friday's northwest winds will also allow for bands of lake-effect snow to develop for regions southeast of Lake Huron and Georgian Bay. In southern Ontario, it is there where the heaviest snows are expected, and driving conditions may become difficult amid blowing snow and reduced visibilities.
"The system snow will continue across eastern Ontario and southern Quebec on Friday, with higher snowfall rates expected across the Eastern Townships and Gaspe," says Kelly Sonnenburg, a meteorologist at The Weather Network. "Temperatures will fall through Friday night with the arrival of much colder air for Saturday morning."
In all, between 10-20+ cm of snow is expected for the hardest hit places through Saturday, with areas like Ottawa and Montreal picking up their first measurable snowfall of the season, with around 5-10 cm expected.
Wet roadways and sidewalks will be extra slick early Saturday and though conditions will improve throughout the day, much colder air will have settled in.
SUNDAY: EYEING A WEAK CLIPPER AND WIDESPREAD LIGHT SNOW
A relatively weak clipper will track across the Great Lakes and southern Ontario during Sunday, with forecasters watching the potential for widespread light snow, which could bring 1-3 cm.
Near or slightly below seasonal temperatures will persist through early and mid next week, with the potential for a couple more clippers to track across the region. It is still too early to have confidence in the track and impacts of those systems.
Be sure to check back for the latest weather updates across Ontario and Quebec.