Significant Freezing Rain Threat for Eastern Ontario Including Ottawa & Kingston on Wednesday
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An approaching system is set to move across Southern Ontario later on Wednesday, leading to a prolonged risk of freezing rain in much of Eastern Ontario. This system will bring warmer air, resulting in foggy and rainy conditions throughout Southwestern Ontario and the Golden Horseshoe area.
As the system advances northeast, it will encounter temperatures below freezing at the surface in Eastern and Central Ontario. The warm air will overtake the colder air aloft, creating ideal conditions for freezing rain.
Current forecasts indicate that the risk of freezing rain could last between 6 to 12 hours in parts of Eastern Ontario, beginning Wednesday afternoon and continuing through the evening into the early hours of Thursday.
In the hardest-hit regions, significant icing is possible, with more than 10mm of accumulation expected by early Thursday morning. This is likely to lead to icy road conditions and potential power outages as ice builds up on tree branches and power lines.
Through the morning hours, drizzle and fog have already been affecting Southwestern Ontario and the Greater Toronto Area. This precipitation is expected to spread northward in the afternoon, meeting the colder air and forming a band of freezing rain from Lake Simcoe eastward through Peterborough to Kingston by mid-afternoon.
This freezing rain will persist, causing steady icing throughout the afternoon and evening. However, there is some disagreement among the models about how long the below-freezing temperatures will last. Some models suggest a gradual warm-up by evening in areas around Lake Simcoe and the Lake Ontario shoreline, which could lessen the ice accumulation in the Muskoka, Belleville, and Kingston regions.
Other models, however, indicate that the cold air will remain firmly in place with little temperature fluctuation until Thursday morning. This scenario would result in widespread icing from this afternoon into early Thursday.
In the Ottawa Valley, especially south of Ottawa, there is more confidence in the forecast. Conditions are expected to be prime for freezing rain from late afternoon into the overnight hours. Further north, in regions like Pembroke, Renfrew, and Ottawa, ice pellets may mix in, leading to less icing but still severe impacts on travel and power.
The freezing rain is expected to taper off in the early hours of Thursday, but with temperatures remaining low in Eastern Ontario, travel conditions will still be treacherous for the Thursday morning commute. Widespread school bus cancellations are likely in this region on Thursday.
Fog will persist in Southwestern Ontario and the GTA. While it may recede slightly later on Wednesday, it's likely to return overnight in some areas.
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Regarding ice accumulation, it's important to note that the amounts mentioned are general estimates of freezing rain from the sky. Actual ice accumulation on surfaces will vary depending on the surface type, and local dynamics are difficult to predict in a broad-scale forecast.
The heaviest ice accumulation is expected between Ottawa and Kingston, with areas like Brockville, Smiths Falls, Perth, Tweed, and Bancroft potentially seeing up to 10 to 15mm of freezing rain. Other parts of Eastern Ontario, including Ottawa, Kingston, and Peterborough, are likely to experience several hours of freezing rain, with ice accumulations ranging from 5 to 10mm.
In Central Ontario and parts of the GTA, lesser amounts of freezing rain are forecast, with around 2-5mm of ice possible for Muskoka, Kawartha Lakes, and parts of York and Durham regions. Less than 2mm is expected for Simcoe County and higher elevations northwest of the GTA. However, these areas could see higher amounts depending on how quickly temperatures rise above freezing.
