Complex Wind Storm and Winter Storm Ahead for Southern Ontario Between Wednesday and Friday

We’re in for a wild rollercoaster ride over the next few days across Southern Ontario when it comes to the weather. This is thanks to a complex system that is expected to become even stronger as it pumps Gulf of Mexico moisture into our region between Wednesday and Friday.

It will all begin early Wednesday morning as we see a steady rise in the temperature bringing all of Southern Ontario well above the freezing mark throughout the day on Wednesday. We are talking about fairly unusual temperatures for this time of the year with daytime highs potentially approaching the upper single digits. It’s possible we may break some temperature records on Wednesday as the record high for most locations range from 3-9°C which is quite likely to be surpassed on Wednesday.

The rise in temperatures across the region will also be accompanied by some very strong wind gusts developing Wednesday morning and continuing into the afternoon. We expect the strongest gusts will be found along the Lake Huron shoreline and through the Niagara Escarpment stretching from Collingwood down into Hamilton. Damaging wind gusts ranging from 90-110km/h are possible in those regions which could result in power outages.

The rest of Southwestern Ontario, around the Golden Horseshoe and east of Georgian Bay can expect wind gusts to max out at around 85-95km/h with power outages also possible. Eastern Ontario and Central Ontario will see slightly lower wind gusts maxing out at somewhere between 80-90km/h, but that certainly isn’t weak so expect some minor wind damage even though they aren’t in the strongest zone.

The wind storm threat should die down as we head into the evening on Wednesday and the first wave of moisture from the system moves into Southern Ontario. This first round will predominately come down in the form of rain as temperatures will remain mild overnight. Those in Northeastern Ontario could see some snow instead of rain as the warmer air likely won’t reach that far north with 5-10cm of snow possible.

Overall we are looking at widespread rainfall accumulation by the Thursday morning/afternoon to range from 10-30mm across Southern Ontario. It appears that Southwestern Ontario and a pocket extending from Georgian Bay and southeastward into the Kingston area will see the highest totals between 15-25mm (locally up to 30mm).

There is some disagreement in the exact intensity and distribution of the moisture with this first round which would affect the overall rainfall totals. That’s why our map might look a little unusual with the random yellow zone including Barrie and Toronto in the middle of all the orange. Some models suggest that a ‘dry slot’ will develop over this region which would result in slightly lower rain totals.

We are looking at less rain through Northeastern Ontario along with Eastern Ontario along the Quebec border. Rainfall totals here will range from 5-15mm with less than 5mm further north where snow will be a bigger issue. This amount of rain combined with a melting snowpack could result in some localized flooding so be aware of that if you live in an area prone to flooding in the spring.

Heavy rain will continue into predawn Thursday, however, a sharp drop in temperature will occur during the morning hours on Thursday starting with Southwestern and Central Ontario. This will be the biggest concern associated with the rainfall as all the moisture on roads and other surfaces will begin to freeze and create icy driving conditions. Be very careful out on the roads during the morning and afternoon on Thursday as the temperature drops. The temperature drop appears to be more gradual so we likely won’t see an official ‘flash' freeze, but the previous rainfall will likely cause issues.

As the temperature drops, this will allow for a transition over to a messy mix of winter precipitation including freezing rain, ice pellets and heavy snow setting the stage for what could be a fairly impactful winter storm. A second push of moisture will move into Southern Ontario late Thursday and last into Friday. There is some uncertainty regarding the speed of the cooldown and track of the system. If the cooldown is faster and the system pushes further to the southeast as indicated by a few models this would make this a snowstorm for Southern Ontario with minimal freezing rain as it’ll stay south of the border.

At this moment, we are going with a more northern scenario with our preliminary forecast as there is more agreement and consistency between the models that show this outcome. Just keep in mind that this is subject to change and we may have to adjust our map southward if the southern trend wins over. To the north, we are looking at heavy snow ranging from 15-30cm which will include much of Southwestern and Central Ontario along with the Ottawa Valley. Again, we may have to reduce these totals on the northern edge of our map if the moisture tracks further south. This includes Muskoka, Simcoe County and Pembroke/Renfrew which may end up closer to 5-15cm if it tracks southward.

The biggest concern for this winter storm is the potential for prolonged freezing rain including Deep Southwestern Ontario, Niagara/Hamilton and Kingston region starting Thursday afternoon and continuing into Friday morning. This area may approach ice storm level with models indicating ice accretion up to 10-15mm and locally even higher. To make matters worse, temperatures will drop even further as we head into Friday so any ice accretion will stick around and continue to cause issues when it comes to travel and the power grid. Power outages are very likely in this zone so be prepared for outages that could linger into the weekend.

Remember that freezing rain is probably the most difficult precipitation type to forecast as it requires a very specific environment to occur. A slight change in the temperature either at the ground or further up in the air could result in the ice storm not happening as we see more ice pellet, snow or regular rain instead of the freezing rain. We want you to be aware of the risk, but hope that the dynamics just don’t align and we see less freezing rain than expected.

There is a tight zone that encompasses much of the Hwy 401 corridor including London, K/W and GTA that is right on the line of seeing freezing rain or snow. It could really go either way depending on the temperature, but we expect a few hours of freezing rain during the day on Thursday before ice pellets and snow mix in by the evening. Ice accretion may range from 2-5mm followed by up to 10-20cm of snow (ice pellets could reduce these totals depending on how fast the switch over occurs).

The precipitation will come to an end by Friday morning as the system moves out of Southern Ontario. It will be followed by another cooldown pushing temperatures well into the negative teens for Friday.

We can’t emphasize this enough: this forecast will likely change! We are providing this very preliminary forecast to help you prepare and have an idea of the potential impacts. However, there is still a lot to work out especially with rapidly changing temperatures that could affect what type of precipitation we see. A more detailed forecast including snowfall and freezing rain accumulation maps along with hour-by-hour timing will be published by Wednesday evening or Thursday morning (if there is still a lot of disagreement amongst the models).