Early Season Snowstorm to Affect Southern Ontario Between Monday (Nov. 11) and Tuesday (Nov. 12)

Published: Sunday, November 10, 2019 - 10:25PM

By Brennen Perry

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It seems like not that long ago when we were talking about double-digit temperatures and heavy rainfall. In fact, it was only 10 days ago around Halloween! Now Mother Nature is diving headfirst into winter with the first Snowstorm of the season for Southern Ontario. We’ve been tracking this system over the past few days and there was a huge amount of uncertainty regarding the track which would affect how much snow our region sees. The latest model runs are in pretty good agreement on a more northern track with the heavy swath of snow reaching our side of the border. Strong north to northwesterly winds will also present another threat in the form of lake enhancement off Lake Huron and Ontario further increasing the potential snowfall from this storm in some areas.

The first impacts of this system are already being felt in areas around Lake Erie and Ontario tonight with light flurries and some accumulating snow. Don’t be surprised when you wake up to barely an inch (2.5cm) of accumulation on the ground in the morning as the snow overnight will be very light. We expect the snow to start to intensify as it slowly encompasses more of our region to the north and east with a band of heavy snow setting up from near Sarnia and extending into the GTHA by noon. Snowfall rates during the afternoon into the evening will range from 1-3cm per hour at the height of this storm with a high impact on the evening commute expected. While the hourly snowfall rate isn’t exactly significant, the issue with this storm is the duration of it with constant moderate to heavy snowfall for 12-16 hours. 

Eastern Ontario will start to see snow around the mid to late afternoon with the heaviest snowfall along the US border and just north of Lake Ontario. The snow will come to an end beginning with the more western section of our region around Lake Huron near the midnight hour as the system progresses to the east. Areas around western Lake Ontario including the GTA will see the snow end between 2-4 AM and finally Eastern Ontario with the snow lingering around until the late morning on Tuesday. Now this won’t necessarily be the end of the snowfall for everyone because some powerful lake effect snow squalls will set up around Lake Huron and Georgian Bay continuing well into Wednesday.

Concerning the accumulation, we’re watching two main zones where lake enhancement could push totals into the 30-60cm range by Tuesday evening. These two zones are the Niagara region and southeast of Lake Huron between London and Sarnia. The bullseye for the Niagara region will include higher elevations away from the lakes in a corridor between Mt. Hope and Niagara Falls.

Lake enhancement will also have the potential to bring 20-40cm for a big region around Lake Huron encompassing Sarnia, Grand Bend and Strathroy. Also, important to note, our forecast includes the snow squalls that will develop southwest of Lake Huron early Tuesday after the storm moves out so that’s why we expect locally up to 60cm by late Tuesday for the Lambton Shores area.

There’s another small zone just south of Georgian Bay including the higher elevation south of Collingwood that may see locally between 20-40cm although that’s less uncertain and might not happen. Outside of the lake enhancement, snowfall accumulation will range from 15-25cm around Lake Ontario and out into extreme Eastern Ontario. Areas bordering the US out in Eastern Ontario like Brockville and Cornwall has the potential to see slightly more between 20-40cm. Away from the lakes will see accumulation drop to the 10-20cm range for much of Southern Ontario. Central Ontario will come out mostly unscathed picking up less than 10cm from this storm. 

As mentioned, snow squall activity will continue well into Wednesday and we have only included the squalls southeast of Lake Huron into our forecasted accumulation. These squalls will lift to the north along with the development of some squalls off of Georgian Bay. The exact location impacted by the squalls from Tuesday evening into Wednesday is a little uncertain at the moment, so we’ll issue a separate forecast on Monday to cover the lake effect activity. 

Stay safe everyone and be sure to drive according to the conditions! If possible, consider avoiding any non-essential travel throughout the afternoon into the evening on Monday as driving conditions will be poor.


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