EARLY PREVIEW: Southern Ontario To Be Impacted by Potential Winter Storm Between Wednesday and Friday

As we mentioned a few days ago, there is the potential for a high-impact winter storm throughout Southern Ontario between Wednesday and Friday. There is still plenty of time for changes to occur so we're careful on being too specific in terms of snowfall totals and precipitation types.

With these events, we thought it would be helpful to break down what stage we are in when it comes to forecasting this storm. We constantly get questions about the impacts on certain cities or towns and it's just way too early to talk about that. Hopefully this will help with easing any confusion on what we can say at this point.

At Instant Weather, we aim to forecast impactful storms in 4 different stages. This begins 5-7 days in advance of a storm where we identify the potential impact it could have on Southern Ontario. We then post a brief 'heads up' update as we did a few days ago. However, we can't say much other than that a storm is possible and how severe the impacts could be on our region.

The focus of this update will be on the second stage outlined in the graphic. We are now around 3 days away from the start of the storm and models are starting to align on what impact it will have on Southern Ontario.

Based on the latest data, it appears that most of Southern Ontario will be on the cold side of this storm with the current track making this mainly a snow event. We could see some mixing especially further to the southeast along the American border from Niagara and out into Eastern Ontario. We are concerned about a swath of prolonged freezing rain associated with this storm, but the latest mode guidances have kept this well south of the border. If the system tracks further to the northwest we may have to talk about a fairly significant icing event for some areas.

There are some similarities between this upcoming storm and the blizzard that affected our region a few weeks ago. We aren't suggesting this will be as significant as the blizzard. That can't be ruled out given the intense totals that models are currently showing, but too early to say for sure. Although the track of this system is quite similar along with the hardest-hit regions.

The current track would result in a swath of heavy snow stretching from Windsor through London, around the Golden Horseshoe and into Eastern Ontario. At this point, there is a fairly good chance for at least 20cm of snow in this region. It's important to note that this event differs in regards to the timeframe. We aren't expecting the bulk of the snow to fall within 6 hours as we saw a few weeks ago. It will come in multiple waves with steady snow over 2 to 3 days. This would give road crews more of a chance to clear the snow instead of getting it all at once. On the other hand, it would extend the impacts over several days with travel delays and school bus cancellations or closures.

There is still some disagreement between the models on the track of the system. Some point towards a more southeastern track with a focus on the GTA/Niagara region and Eastern Ontario. While others show a more northwestern track and a widespread snowstorm that affects almost all of Southern Ontario. This is why we aren't including a snowfall accumulation map because the track is still to be determined.

We are continuing to go over the latest data and hope to have our first preliminary forecast with accumulation maps on Monday.