A fall chill will linger in the air over Ontario for the first half of the week as a cool centre of high pressure flexes its influence on the region.
This setup will make for some headaches on Tuesday, as a messy system approaches the Great Lakes. You could face some tough travel conditions ahead if you haven’t put on your winter tires yet.
Beyond, while forecasters were looking at a threat for lake-effect snow late this week, a considerable change in the computer models has backed off the intrusion of Arctic air. This shift is good news for folks rooting against lake-effect snow.
Dynamic setup threatens wintry mix
A weak Colorado low will meet up with a trough over the Great Lakes on Tuesday, creating a mess across portions of Ontario by the evening commute.
The region will face the whole spectrum of precipitation types as we progress through the second half of Tuesday.
Most of southwestern Ontario will face a cold rain. Temperatures hovering just above the freezing mark could allow for snow to fall north of Guelph and the Greater Toronto Area (GTA).
There’s even a risk of a wintry mix with isolated freezing rain near Orangeville, but it’s not expected to be widespread or disruptive.
In all, a widespread 10-20 mm of rain is expected, with some locally higher amounts possible through Wednesday morning.
Late Tuesday evening, heavier snow spills across eastern Ontario with rain showers winding down through the evening and overnight for the GTA.
We can’t rule out the potential for a few centimetres of slushy, wet snow across northern portions of the GTA, particularly north of Highway 407.
The largest snowfall with this system will likely occur across eastern Ontario, where totals could push 8-10 cm as the system eases in the pre-dawn hours Wednesday.
WATCH: Winter weather creeping close to Toronto for Tuesday's commute
Lake-effect snow potential looking less likely
Models are backing off the threat for the coldest Arctic air descending across the Great Lakes, which will dampen the amount of lake-effect snow bubbling across the region.
The sharp temperature boundary will prove favourable for an additional system swinging through into the weekend. Temperatures will remain within a couple of degrees normal across the south, but up to several degrees below normal in northern Ontario.
Stay tuned to the Weather Network for the latest forecast updates across Ontario.