When you wake up on Saturday it might seem like this storm isn’t as bad as is being forecasted with mild temperatures well above the freezing mark and rainfall, but don’t let that fool you! Temperatures will drop rapidly throughout the day on Saturday resulting in a transition over to wintry precipitation beginning with freezing rain and moving over to ice pellets or snow further north. Some areas, particularly just north of the GTA, eastward through Peterborough and into Brockville could easily see 16-24 hours of constant heavy freezing rain. The freezing rain will begin just after the lunch hour on Saturday and last through the day and into Sunday morning so conditions will be at the worst late Saturday and during the overnight hours. Strong wind gusts will also develop early Sunday after all the icing gusting up to 50-80km/h during the morning and afternoon which would further complicate the situation and likely result in many power outages. We will focus more on the wind gusts with a seperate forecast to be posted Saturday once we get an idea on the exact strength of the wind risk.

There’s a lot to talk about with this upcoming storm as the actual impact will be vastly different across the province. We’re going to start with the potential ice storm, but the flooding risk is certainly not to be ignored so continue reading below for details on that. As mentioned, some rain will start the day for many on Saturday although we’ll begin to see a line of freezing rain develop from Britt to North Bay around 5 am as cold air begins to cause temperatures at the surface to drop below the freezing mark. This thin line of freezing rain will begin to expand as it moves southward - areas roughly north of a line from Bracebridge to Renfrew will see a few hours of freezing rain in the morning or early afternoon hours before switching over to an ice pellet and heavy snow mix. By Saturday late afternoon, we’ll see a fairly expansive area of heavy freezing rain develop from Goderich through Orangeville, Northern GTA and into Ottawa. Areas to the north from Owen Sound to Bancroft will see mostly ice pellets while those closer to the Lake Ontario shoreline will hold onto the rain for a few more hours with slightly warmer temperatures.

The tricky part of this forecast where lots of uncertainty remains is an area through K/W, the GTA and along the Lake Ontario shoreline out into Eastern Ontario as we’re not quite sure how quickly temperatures will fall below the freezing mark if at all. We’ve highlighted this ‘uncertain’ area with the green dashed line on our map above. If the cold air makes it that far south and causes temperatures to get below zero by Saturday evening it would be a very dangerous situation with heavy freezing rain continuing overnight and into Sunday morning. On the other hand, if temperatures can stay even just a fraction above zero past midnight resulting in more rain then it will greatly reduce the ice storm threat for that area. The bottom line is that you should be prepared for a very impactful ice storm including through the GTA but don’t be surprised to see this storm be a big ‘bust’ in those areas. We’ve gone on the lower side for the City of Toronto with 2-6mm of ice accretion close to the lakeshore and 6-12mm in the north end of the city although it’s conceivable to see much higher totals should the colder scenario play out.