Winter Storm Threatens Tuesday Evening Commute Across Ontario Including the GTA; Significant Snowfall to the North With Up to 35cm Possible
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The New Year in Ontario has been notably active, marked by several snowy systems over the past week. This trend is expected to continue with a significant winter storm approaching, bringing heavy snow, ice pellets, and some freezing rain beginning Tuesday morning.
We are also closely monitoring a potential high-impact storm this weekend, which may deliver a more substantial impact, focusing on heavy snow rather than mixed precipitation.
More details about the looming snowstorm threat will be provided in the coming days. For now, our attention is on the imminent winter storm, which presents a complex forecast involving various winter weather threats. Weather models have struggled to determine the exact path of this system, but there is broad agreement as we approach 24 hours before the system's arrival.
The heaviest snowfall is expected to occur primarily in Northeastern Ontario, extending southward into Central and Eastern Ontario. In these areas, precipitation is likely to remain frozen for most of the event, resulting in higher snowfall totals. By early Wednesday, the hardest-hit areas could see over 20cm of snow, with some locales receiving more than 30cm.
In the rest of Southern Ontario, the scenario is more complex. We anticipate wet snow in most regions on Tuesday morning, transitioning to rain as temperatures rise, beginning in Deep Southwestern Ontario and around the Lake Huron shoreline.
The speed of the warmer air's advance northward creates uncertainty regarding overall snowfall accumulation. Strong wind gusts accompanying the icy mix may reduce visibility and cause blowing snow.
By Tuesday afternoon and evening, a large portion of Southwestern Ontario and the Golden Horseshoe is expected to shift to ice pellets and then rain. This transition may coincide with peak evening rush hour, potentially leading to hazardous travel conditions. We advise preparing for extended travel times or considering staying off the roads until conditions improve.
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To clarify the timeline of the various precipitation shifts, we will detail the expected impact of this winter storm for each part of Tuesday and Wednesday.
Focusing on the timeline rather than the amounts is crucial, as accumulating snow at the storm's onset will likely be washed away by rain, making accurate measurement challenging. The rapid shifts in precipitation types, leading to icy and slushy road conditions, are the main threat of this winter storm.
The storm will begin early Tuesday morning as initial bands of precipitation cross into Deep Southwestern Ontario. Heavy wet snow is expected in Windsor, Chatham, Sarnia, London, and the Niagara region, transitioning to rain by late morning.
Further north, colder air will result in more prolonged snow across the Golden Horseshoe and westward through the Kitchener region. Ice pellets may mix in, especially along the Lake Ontario shoreline and south of the Hwy 401 corridor.
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As the afternoon progresses, the storm will intensify across Southern Ontario. Areas in Deep Southwestern Ontario and along the Lake Erie shoreline into the Niagara region will have switched to rain, minimizing the impact.
There is uncertainty in the Lake Huron shoreline and the Greater Toronto Area, where precipitation types will vary due to slight temperature differences.
Areas closest to the shoreline, including Hamilton, Burlington, Mississauga, and Toronto, will see a mix of ice pellets and snow during the early afternoon. However, by late afternoon, some rain is expected to mix in.
Regions north of the Hwy 401 corridor are likely to experience continued heavy snow mixed with ice pellets at times. Combined with strong wind gusts of 60-80km/h, travel could be difficult due to blowing snow and ice pellets.
A slight risk of brief freezing rain exists in this area, although sustained freezing rain is unlikely. The more likely progression will be from snow to ice pellets to rain.
Heavy snow will also affect Central Ontario around Lake Simcoe and eastward along the Lake Ontario shoreline into Eastern Ontario. Expect several hours of heavy snow throughout the afternoon.
Those in the Quebec border area and the Ottawa Valley will see the first snow bands by late afternoon, starting with lighter snow and intensifying later.
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By evening, warmer air will begin to replace the cold air, leading to a wider transition from frozen precipitation to rain. Southwestern Ontario and the Golden Horseshoe will have mostly switched to rain.
In southern parts of Central and Eastern Ontario, snow will persist into the early evening, potentially mixing with rain near midnight.
Heavy snow will continue for the Quebec border and Ottawa Valley regions throughout the evening. Ice pellets may mix in, extending from north of Parry Sound through Huntsville to the Smiths Falls and Cornwall areas.
Northeastern Ontario is expected to see persistent heavy snow from late Tuesday afternoon through the night. Little mixing is anticipated in this area.
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The storm will persist into early Wednesday, primarily affecting northern parts of Central and Eastern Ontario. South of a line from Bracebridge to Smiths Falls is expected to switch to rain by midnight.
Heavy snow will continue in the Ottawa Valley and Northeastern Ontario. By mid-morning, some mixing, including ice pellets and potentially freezing rain, is expected.
By sunrise, most of Southern Ontario will have switched to rain, while snow continues in Northeastern Ontario. The Ottawa region may not experience this transition if warmer temperatures fail to displace the cold air. Wednesday morning's commute in Eastern Ontario, especially the Ottawa Valley, is likely to be challenging.
As the system leaves the region, temperatures are expected to drop below freezing by early Wednesday morning in Southwestern Ontario and late morning or early afternoon in the rest of Southern Ontario. This will result in a transition back to wet flurries later on Wednesday, although significant accumulation is unlikely.
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While the variety of precipitation types is a key story of this storm, overall snowfall accumulation in some areas will resemble a classic snowstorm rather than a messy winter storm.
Starting with the least affected region, Deep Southwestern Ontario and the Niagara region are expected to see less than 5cm of snowfall, primarily on Tuesday morning before being washed away by rain.
Snowfall totals along the Hwy 401 corridor from London through Hamilton to the GTA are expected to be around 5 to 10cm early on Tuesday before switching to rain. This forecast is tricky, as slight temperature variations can significantly affect snowfall amounts. Thus, focus less on specific amounts in this region.
Areas north of the Hwy 401 corridor and away from the Lake Ontario shoreline are likely to see prolonged heavy snow throughout Tuesday morning and afternoon. Snowfall totals could reach 10-15cm in some areas, especially in higher elevations around the Dundalk Highlands, Kitchener, and Guelph regions, where some models suggest localized totals may exceed 15cm.
This zone, encompassing much of southern Central and Eastern Ontario, has more variance, leading to a wider range of 5cm to 15cm in snowfall totals. This forecast acknowledges the uncertainty in this area, providing a complete picture rather than a definitive prediction.
Further north, snowfall totals of 10 to 20cm are expected from Parry Sound through Muskoka to the Tweed and Cornwall areas.
Even higher totals are anticipated in northern Central Ontario, including Sundridge, Bancroft, and the Ottawa Valley, with a general range of 15-25cm possible. Localized pockets may even see up to 30cm.
The Algonquin Park, Renfrew, and Pembroke areas are forecasted to be the worst hit in Southern Ontario, with expected snowfall between 20 to 35cm.
In addition to snowfall, significant rain and wind are associated with this system, particularly in the south. Rainfall totals will range from 30 to 50mm across Deep Southwestern Ontario, along the Lake Erie shoreline, and into parts of Eastern Ontario north of Lake Ontario.
Rainfall totals will decrease further north, with around 20 to 30mm expected along the Lake Huron shoreline and into the GTA near Lake Ontario. For southern parts of Central and Eastern Ontario, rainfall totals between 10 to 20mm are expected, but actual precipitation will be higher when melted snow is considered, raising flooding concerns.
Less than 10mm of rain is anticipated for more northern parts of Central and Eastern Ontario, as they are likely to remain predominantly on the cold side of the storm.
Strong to damaging wind gusts are also a risk during Tuesday afternoon and evening. While there is some disagreement on the intensity, some models suggest gusts could approach 90-100km/h around the Lake Erie shoreline, Niagara region, and Prince Edward County.
For the rest of Southwestern Ontario into the Golden Horseshoe, wind gusts will range from 50 to 70 km/h, with a slight chance of 70-85 km/h gusts if the more intense model proves accurate.
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For Northeastern Ontario, the event will primarily be a snowstorm, starting Tuesday afternoon and continuing into Wednesday afternoon.
Snowfall totals are expected to be significant, with the hardest-hit regions from Manitoulin Island through Sudbury, North Bay, and into the Kirkland Lake region anticipating 20 to 35cm, with some areas possibly reaching 40cm.
Lower amounts are forecasted further west, with 15 to 25cm expected in areas including Elliot Lake, Timmins, and Cochrane.
Closer to Lake Superior, including Sault Ste. Marie, Wawa, and Kapuskasing, around 10 to 15cm of snow is expected, although this may vary by location. For a more detailed forecast, refer to the accompanying map.
In summary, this winter storm brings a mix of precipitation types across Ontario, with varying impacts depending on the region. The forecast includes heavy snow, rain, and strong winds, with significant snowfall in certain areas. Residents should stay informed and prepare for potentially hazardous travel conditions.
