Messy Week Ahead as Multiple Rounds of Heavy Snow and Freezing Rain Target Southern Ontario Starting Tuesday
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After a mild start in December, the new year has brought a shift in the weather pattern across Southern Ontario. January has definitely felt more like winter, with our first prolonged deep freeze leading to several instances of snow squalls in the past few weeks.
However, it seems the winter spell is about to break as we welcome milder air for the final days of January. The warm-up won't be uniform across the region, though. For instance, the Ottawa Valley and northern parts of Central Ontario will continue to experience colder temperatures, with overnight lows below -10°C and wind chills near -20°C for much of the week.
In contrast, areas in Southwestern Ontario and around the Golden Horseshoe are expected to see temperatures closer to, or even slightly above, the freezing mark later this week.
Several systems are forecast to move across Southern Ontario in the coming days. With temperatures hovering around freezing, these systems are likely to bring a mix of winter weather, including heavy snow, ice pellets, freezing rain, and even some regular rain.
The first system is set to impact Southern Ontario late Monday, continuing through Tuesday. This could affect the Tuesday morning commute, particularly in Southwestern Ontario and the Greater Toronto Area.
Current predictions indicate that precipitation will primarily be heavy snow, stretching from Lake Huron across the Golden Horseshoe and into southern parts of Central and Eastern Ontario. By Tuesday's end, total snowfall could reach up to 10cm in some areas.
A more complex situation is expected further south in Deep Southwestern Ontario and along the Lake Erie shoreline. A mix of snow, ice pellets, and prolonged freezing rain could lead to icy road conditions in this region.
Light snow and ice pellets have already started in Southern Ontario as of Monday afternoon, ahead of the main system. This is expected to taper off through the evening, though some patchy freezing drizzle could persist around the Lake Erie shoreline.
The initial bands of precipitation associated with the system will reach the Windsor area around midnight, with freezing rain being the primary concern. This risk will continue overnight and spread to Chatham and Sarnia by mid-morning Tuesday, making for potentially icy roads and delays. School bus cancellations are also a possibility due to the freezing rain threat.
By lunchtime Tuesday, the slow-moving system should reach London, Kitchener, Hamilton, and Toronto. It will likely start as light to moderate snowfall, continuing into the evening. Although the snowfall rates may not be intense, the prolonged nature of the event means that even a centimetre or two per hour will accumulate significantly over 6-12 hours.
Later in the afternoon, areas in Deep Southwestern Ontario and along the Lake Erie shoreline should warm up enough to transition from freezing rain to regular rain. A similar changeover to ice pellets and freezing rain is anticipated in the London to Hamilton corridor by evening, possibly resulting in slightly lower snowfall totals compared to areas further north.
Snow is expected to begin in the southern part of Central and Eastern Ontario, from Barrie to Kingston, in the late afternoon or early evening, continuing overnight into Wednesday morning. Further north, areas like Huntsville, Algonquin Park, and Ottawa can expect less snow, as the heaviest precipitation is forecast to remain south.
The system should start clearing from west to east just after midnight and exit the province by late Wednesday morning. However, a brief respite in precipitation will be followed by another wave of moisture from the southwest late Wednesday.
This next system looks to bring more rain for Southwestern Ontario and the Golden Horseshoe, while Central and Eastern Ontario could face a prolonged risk of freezing rain lasting into Thursday. Further details on this will be provided in a separate forecast.
The impact of the first system will vary significantly. Regions east of Lake Huron through the Kitchener area and around the Greater Toronto Area are likely to see mostly snow, with additional accumulations of 6 to 12cm by the end of Tuesday. Lower snowfall amounts of 2 to 6cm are expected further north in parts of Central and Eastern Ontario.
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The situation becomes more complex southwestward, with a zone stretching from Sarnia through London to the Hamilton/Niagara region likely to experience a mix of ice pellets and snow. A few centimetres of ice pellets, along with up to 4-8cm of snow, is possible here. Brief freezing rain later on Tuesday shouldn't be ruled out as the mixing line moves northward.
In Deep Southwestern Ontario and along the Lake Erie shoreline, the primary risk is ice pellets and freezing rain. The precipitation will likely start as ice pellets early Tuesday, transitioning to freezing rain by late morning or early afternoon. Some rain may also occur in the evening as temperatures rise above freezing. Total accumulations are hard to gauge, but expect around 2-6cm of snow, followed by up to 2cm of ice pellets, and then several hours of freezing rain.
The Windsor and Chatham areas are forecast to see mostly freezing rain from this system, with ice accumulation up to 2-4mm before transitioning to regular rain. There could also be 10-15mm of rain from the system after the switchover occurs.
