Yet Another Messy System for Southern Ontario on Wednesday; Up to 10–20cm of Snow Through Central Ontario

It might have been a slow start to the winter season across Southern Ontario, but Mother Nature has been making up for it in the past week. This continues as we’re watching what will likely be the last system of 2020 for Southern Ontario on Wednesday. The track of this system will be quite similar to the one we saw a few days ago with heavy wet snow through Central Ontario and parts of Bruce-Grey counties while the rest of Southern Ontario sees mostly rain. We expect the heaviest snowfall accumulation will be found east of Lake Huron and Georgian Bay thanks to some lake enhancement. Those areas could see between 12-20cm of snowfall accumulation by the end of Wednesday.

We’ll begin to see that first bands of precipitation work their way into the province predawn Wednesday from Michigan. Current data suggests it will likely begin as some light to moderate wet snow for most areas with some rain mixing in around Lake Ontario and Erie towards the later morning hours. Heavier pockets of snowfall are expected to affect the Grey-Bruce and Muskoka region into Northeastern Ontario due to some lake enhancement.

Some data suggests there might be the potential for an hour or two of light freezing rain Wednesday afternoon from Goderich through Orangeville/Barrie and eastward through Peterborough, but other models show this as mostly ice pellets or regular rain. Regardless, be prepared for some icy driving conditions in those areas. Like last time, the mixing line will be roughly near Lake Simcoe so areas to the north of Lake Simcoe will see the snow continuing into the evening hours while those to the south see a switch over to rain sometime through the afternoon. Precipitation will start to taper off late Wednesday around midnight although flurries may linger into Thursday particularly around Georgian Bay where some lake effect snow may develop.

As we’ve said, the accumulating snowfall will be mostly contained to those to the east of Georgian Bay and higher elevations east of Lake Huron. Locations like Owen Sound, Bruce Peninsula, Muskoka/Parry Sound and Elliot Lake can expect accumulation between 12-20cm from this system. A few localized amounts near 25cm is possible mainly to the east of Georgian Bay if we see squalls develop late Wednesday as the system moves out of the region. Other areas like Sudbury, North Bay, Bancroft, Northern Simcoe County and Kincardine/Goderich will see about 6-12cm of snowfall accumulation although they could see less due to ice pellets and freezing rain mixing in. The rest of Southern Ontario can expect less than 2cm of accumulation except for the Kitchener/Waterloo, Barrie and Ottawa area who could see as much as 6cm depending on how fast the snow to rain transition occurs.

We are also continuing to keep a close eye on that potential New Years’ winter storm for Southern Ontario starting sometime on Friday lasting into Saturday. The latest model guidance shows a fairly robust freezing rain threat for parts of Southwestern, Central and Eastern Ontario. Ice accretion of between 5-10mm is not out of the question in the hardest-hit regions. It doesn’t appear to be particularly significant at this point but that could change depending on how the system develops. We’ll have more details in the coming days as we have more certainty in the potential impact on Southern Ontario.