Winter Is Not Done Yet! Parts of Southern Ontario Could See Up to 10-20cm of Snow by Monday
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Southern Ontario's recent spell of balmy weather made it feel like an early spring, yet winter has swung back into our forecast. A return of colder air has arrived just in time for the weekend, bringing a fresh batch of lake effect snow—aided by the unusually open waters after our mild winter.
Lake effect snowfall is expected to predominantly impact the southern shores of Lake Huron starting late Saturday and persisting into Sunday. The most affected regions could amass snow totals nearing 15 to 20cm by the end of Sunday.
Simultaneously, the outer bands of a system tracking up the Northeastern United States might deliver accumulating snow, primarily to Ontario's far eastern regions beyond Ottawa. These areas could see accumulations of 10 to 15cm by Monday morning.
As of Saturday evening, we've witnessed a temperature dip across Southern Ontario, with expectations for the mercury to descend below freezing overnight. This shift sets the stage for lake effect snow development along the Lake Huron and Georgian Bay shorelines, particularly overnight and into Sunday morning.
Heavy lake effect snow is forecasted for areas stretching from Goderich to southward through Grand Bend and even into London, and south of Georgian Bay, encompassing the Meaford and Collingwood area.
The peak of this lake effect snow event is predicted for the pre-dawn hours on Sunday, continuing into early afternoon and gradually lessening by evening.
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Snow Squall Accumulation Disclaimer
Forecasting the exact snowfall accumulation for a specific location in a lake-effect snow event is extremely challenging. This is because of the highly localized nature of snow bands, which can lead to significant variance in totals even over short distances.
Therefore, you may notice our forecast shows significantly more snow than your weather app (including our own app). App-based forecasts often struggle with lake effect snow events due to their localized nature and reliance on data focused on larger macro-level weather events. This results in a failure to accurately capture the squalls, which operate at a micro-level, leading to intense snowfall totals.
Our forecast may still be off if the wind direction varies slightly from what the models predict, causing the snow squall band to form further north or south. That's why our forecasts use broader zones to account for this variability, meaning not everyone within these zones will see the significant totals. Essentially, we're indicating that a location within this area could see the forecasted amount.
The latest data indicate the most substantial snowfall will be found in areas like Goderich, Grand Bend, Lucan, and London, where totals may surpass 10cm, with localized areas potentially receiving 15-20cm. Elevated regions southwest of Collingwood are also likely to see over 10cm of snow.
Neighbouring regions such as Port Elgin, Wingham, St. Thomas, Meaford, and Collingwood might see up to 10cm, depending on the strength of the lake-effect snow. Lesser amounts, under 5cm, are anticipated for the rest of Southwestern Ontario and the Golden Horseshoe.
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Beyond the lake effect, heavy snow is forecasted to develop overnight in far Eastern Ontario as outer bands of precipitation from the slow-moving Eastern Seaboard system linger in the region.
Persistent snowfall will continue across areas east of a line from Kingston to Ottawa throughout Sunday, possibly continuing overnight before fizzling out just after Monday's sunrise.
Regions including Hawkesbury, Alexandria, and Cornwall could see totals exceeding 10cm by Monday morning. The area from Ottawa south to Brockville might approach snowfall close to 5cm. As we move westward, expected accumulations will quickly decrease, with less than 5cm forecasted due to the sharply declining precipitation gradient.
