Chris Scott, meteorologist
A large, sprawling area of low pressure will slowly start to take shape across the U.S. Plains Sunday into Monday. The energy for this storm is coming from two systems – one currently producing snow across southeast B.C. and southern Alberta, and a separate system that will give San Francisco some light rain through Sunday. Once this storm really takes shape on Tuesday – the centre of low pressure likely being close to Memphis late Tuesday – it will lumber northeast with a huge swath of precipitation reaching from St. Louis to Toronto and eventually into the U.S. northeast.
Our forecast team’s current thinking is that the storm will track up through the Ohio Valley, with the centre staying just south of the Great Lakes. This type of track has the potential to produce heavy snow (20+ cm) across Southern Ontario. Freezing rain could be a significant threat in parts of the Ohio Valley Monday night into Wednesday morning, and if the system tracks a little further west, some ice pellets or freezing rain could move as far north as Southern Ontario.
Most of the computer models suggest that some snow is likely on Tuesday in Southern Ontario, well in advance of the main system. There is one model (the Canadian Global Envrionmental Multiscale Model – or what we call the GEM) that takes the low far enough south on Wednesday that the heaviest snow would miss Toronto and entirely miss Ottawa and Montreal. However, we think the likelihood is that the storm will track closer to the Great Lakes, giving the most widespread winter storm so far this season to most of Southern Ontario, and possibly Southern Quebec, with the highest impact around the Golden Horseshoe including Toronto and Hamilton.
The way it's looking right now is that this storm could come in a couple waves, with an initial shot of snow Tuesday across Southern Ontario, with the real meat of the storm Tuesday night into Wednesday. If this scenario pans out, Wednesday would be the worst travelling day throughout the 401 corridor. Ottawa and Montreal have had an especially easy go of it so far this winter, but this storm may end that stretch if it does track far enough to the north. And of course, there will likely be some impact on the Maritimes, late Wednesday into Thursday.
This storm will have a significant impact on North American air travel, so you’ll need to keep a close eye on this one if you have flight plans over the next couple days.
We’ll be updating our forecast as new information comes in, so keep checking theweathernetwork.com for the latest.
You can also receive updates on your cell phone to ensure you're prepared for the stormy weather.