Sliding temperatures, an incoming cold front, and still relatively warm lakes – it's looking like a favourable setup for what could be the first lake-effect snow event for parts of southern Ontario in the traditional snow belts. Bands of lake-effect snow develop southeast of Georgian Bay and Lake Huron later Sunday, some areas could be looking at 10-15+ cm of snow through Monday. More on how this weekend shapes up, including the overall pleasant conditions for Halloween, below.
Broad upper trough over the Great Lakes maintains instability over the region
Lingering flurries or light snow for parts of the southwest peter out by Friday morning,
Significant snow squall threat Sunday into Monday, travel will be impacted
FRIDAY INTO SATURDAY: COLDEST DAY OF THE WEEK, COLDEST TEMPERATURES SINCE MAY
Some lingering flurries, perhaps even scattered light snow, for parts of the southwest will be largely a memory by Friday morning. Beyond, the skies look set to clear across the south through the morning, but don't let that fool you: Blustery conditions, driven by a gusty north wind, will bring the coldest air of the season so far.
Wind chill values for the early morning hours will leave things feeling closer to a frigid -10 across the region.
As well, a northeast flow off of Lake Ontario Friday could also stir up some lake-effect flurries across the Niagara region through parts of Friday.
Temperatures will rebound slightly into Saturday, making for a sunny, but still chilly, Halloween day.
SUNDAY INTO MONDAY: PERFECT SET-UP FOR SIGNIFICANT LAKE-EFFECT SNOW
The origin of what could be the first widespread shot of lake-effect snow for southern Ontario's traditional snow belts is already brewing in the west: A low-pressure system gradually tracking toward Ontario through the late week.
It's set to bring rain and snow to the northwest and Nickel Belt, while its cold front will pass through southern Ontario. Showers will be relatively widespread through the day Sunday, but the cold front looks likely to trigger the lake-effect snow machine, bringing bands of snow streaming inland from Lake Huron and Georgian Bay Sunday evening through much of Monday morning – even stretching into parts of the northern GTA.
This set-up could have quite an impact on travel through the snow belts, especially if the squalls sit over one area for an extended period of time.
"The instability is robust and the winds will generally stay locked into that northwest zone, so someone could likely exceed 30+ cm of snow," warns Weather Network meteorologist Tyler Hamilton.
WARMING THROUGH EARLY NOVEMBER
Next week will start on another cold, and potentially record-breaking note, as cold air crosses the Great Lakes Sunday night and into Monday. Temperatures aloft will be more typical of mid-to-late December, with a record cold high temperature of just 2°C forecast for Monday in Toronto.
It won't take long, however, for the warmer weather to nudge back in.
"An extended period of near to above seasonal temperatures are expected through the second week of November with temperatures more typical of mid-October," says Weather Network meteorologist Dr. Doug Gillham.
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