First Strong Snow Squall Event of the Season Could Bring Significant Snowfall to Parts of Southern Ontario Starting Sunday
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Winter is settling in across Ontario as we approach the end of November, and early next week marks the arrival of the coldest air so far this season, featuring temperatures well below the freezing mark.
By Tuesday, some parts of Northern Ontario, as well as the northern sections of Southern Ontario, could experience double-digit negative temperatures, even before factoring in the wind chill.
This frigid blast of cold air is triggering what appears to be a robust lake effect snow event in the traditional snowbelt region around Lake Huron, Lake Superior, and Georgian Bay. Locally intense snow squalls are anticipated to develop from Sunday evening, persisting through Monday and into Tuesday.
A potential secondary round of snow squalls may emerge starting Wednesday, though the exact location and intensity remain uncertain, which will be covered in a separate forecast in the coming days.
While still a few days away, most models are converging on a general consensus regarding the hardest-hit regions of these squalls, primarily driven by a northwesterly flow. However, variations in expected accumulation will become clearer as higher-resolution models come into view.
On Sunday, a weak system is forecasted to track through Southern Ontario, bringing some flurries and mixed precipitation across the region. Nevertheless, any snowfall accumulation is expected to be minor, with only a few centimetres possible.
As the system exits the region by late Sunday, colder air from the north will usher in lake-effect snow off Georgian Bay and Lake Huron as early as Sunday evening. Initially disorganized, the lake effect activity is likely to focus on areas northeast of the lake, with the Bruce Peninsula and Parry Sound region experiencing locally heavy snow.
By Monday morning, the lake effect snow will shift southward, intensifying as the environment becomes more favourable for snow squalls.
Current indications suggest two distinct squalls, with one stretching across the Bruce Peninsula, over Georgian Bay and coming onshore between Barrie and Orillia. A secondary squall is expected further south, predominantly affecting the Port Elgin, Owen Sound, Hanover, and Kincardine regions.
There is potential for these squalls to persist for up to 12-16 hours starting Monday afternoon and continuing into Tuesday morning. The exact location of the squalls is challenging to pinpoint at this stage, dependent on wind direction, strength, and temperature. If they lock in place, locally intense snowfall rates may lead to rapid accumulation and hazardous road conditions due to near-zero visibility, accompanied by blowing snow.
The snow squalls may continue into Tuesday, with the most intense conditions likely between Monday evening and Tuesday morning, gradually improving throughout the day. A shift in wind direction by Tuesday evening may temporarily halt the lake effect, but squalls could return overnight into Wednesday, focusing on regions southeast of Lake Huron, including Grand Bend and even London.
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We've outlined a rough idea of where the worst impacts from the lake effect snow are expected between Monday and Tuesday. Please note that this is preliminary, and the forecast zones will be refined in the coming days as higher-resolution models become available.
Regions in the strong impact zone include Port Elgin, Chatsworth, Owen Sound, Hanover, Flesherton, Midland, and Simcoe County. Some locations within this zone could see hefty snowfall totals approaching 25 or even 50cm.
The rest of the regions east of Lake Huron and Georgian Bay can expect a moderate impact from snow squall activity, with up to 25cm of snow possible. The Georgian Bay squall may extend quite far inland at times, affecting parts of Durham region and Kawartha Lakes.
While lake effect activity off Lake Ontario and Erie is expected to remain mostly stateside, it could briefly drift north late Tuesday, leading to heavy snow in the southern part of the Niagara region and Prince Edward County. Locally, 5-10cm of snow is possible within a few hours.
Turning our attention to Northern Ontario, snow squall activity off Lake Superior is anticipated to be relatively weaker than those off Georgian Bay and Lake Huron. However, we could still see up to 25cm throughout the Sault Ste. Marie and Wawa area, primarily on Sunday and early Monday.
