An unusual clash of the seasons will take shape across southern Ontario this weekend, as a rare November thunderstorm threat gives way to some widespread wet snow on Sunday. The snow is courtesy of an Alberta clipper set to track through late in the weekend, bringing a mix of rain and snow, with some locally heavy totals possible. Like most mid-November snow events however, accumulations will be highly dependent on elevation and distance from Lake Ontario, but some areas could wind up see about 10 cm through early Monday. More on this incoming snow and the thunderstorm risk that pops up first, below.
FRIDAY: TEMPERATURES BRIEFLY REBOUND AHEAD OF COOLER WEEKEND
While Friday won't feature the same 20-degree daytime highs that kicked off this week in southern Ontario, temperatures will be running a few degrees above seasonal once again, thanks to a southerly flow that will see highs hovering close to the mid-teens.
Rain showers associated with a potent system that's brought significant snow to northwestern Ontario will then track across the region later in the evening, with even the chance for some non-severe thunderstorms to rumble through.
The flow off the relatively warm waters of Lake Huron and Georgian Bay, combined with colder air aloft will allow for this pocket of instability and the chance for stronger storms to develop in places like Subury and Parry Sound Friday evening.
More widespread rain will then pick up through the overnight hours, possibly mixing with wet snow for some areas into Saturday morning.
SATURDAY INTO SUNDAY: COOLER TEMPERATURES SET THE SCENE FOR WIDESPREAD WET SNOW
Mostly cloudy conditions will span the region for Saturday, with colder temperatures and a gusty wind. While most of the day looks to remain dry, we can't rule out the chance for a passing rain and snow shower.
Lake-effect rain and snow showers are likley for areas north and west of the Greater Toronto Area however, and also for parts of the Niagara region near Lake Erie.
By Sunday afternoon, an Alberta clipper is set to track across southern Ontario, bringing a more widespread mix of rain and wet snow that will continue through Sunday night.
"Wet snow will be the dominant precipitation type across most of southern and central Ontario, but areas near Lake Ontario and Lake Erie (including most of the Greater Toronto area) will see primarily rain, which could change to wet snow before ending during Sunday night," says Dr. Doug Gillham, a meteorologist at The Weather Network.
This will be a typical mid-November snow event however, where snow totals will highly dependent on elevation and distance from Lake Ontario.
While little to no accumulation is expected across most of the GTA and Niagara region, for the higher terrain north and west of the GTA, widespread snow totals of 2 to 5 cm are likely, with localized totals of 5 to 10 cm possible.
"The highest snow totals are expected across the Dundalk Highlands south of Georgian Bay, in the Orangeville area, near and north of the Kitchener-Waterloo region and also across the Halliburton Highlands," Gillham adds.
BEYOND: CHILLY WEATHER FOR EARLY NEXT WEEK, BANDS OF LAKE-EFFECT SNOW
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.
Bands of lake effect snow are also likely southeast of Georgian Bay and Lake Huron on Monday.
Be sure to check back for the latest updates on the changing pattern across Ontario.