Potent low may bring hefty wintry blast to southern Ontario next week

Digital WritersThe Weather Network
Digital Writers

As we move closer to December, forecasters are closely watching the threat for some impactful storms and a more 'typical' winter pattern setting up for southern Ontario.

After a calm and mostly sunny Saturday, Sunday looks even rosier, with daytime highs tipping close to the double digits. But by Monday, a stormy pattern sets up for the first half of the week, with a chance for rain and snow in southern Ontario through to Tuesday and even into early Wednesday for some people. We note, however, that there is still some uncertainty of the incoming system's track. Read on for what we know, along with a look at a more typical early winter setup as we move through December.


  • Sunday mostly clear and sunny, temperatures close to double digits

  • Storm system moves in later Monday, threat for heavy rain and snow for some

  • Cooler pattern beckons for early days of December


After a calm and mostly clear weekend, Monday will feature an active pattern setting up, something that may continue to persist through the first half of December, as well.

WINTER FORECAST: On Monday, November 30 The Weather Network releases the official 2020/21 Winter Forecast. Tune in!

The first shot of stormier weather will come courtesy of a low developing along the Texas coast, tapping into Gulf moisture as it intensifies, then tracking northeast or just east of the Appalachians and into southern Ontario on Monday.


"A blocking pattern over the Atlantic will trap the system and cause it to stall in the vicinity of southern Ontario through the middle of next week," warns Weather Network meteorologist Dr. Doug Gillham.

With average temperatures in place, widespread heavy rain and strong winds look to be the main threats for much of the region for Monday and Tuesday.

While most of Monday will see mostly rain, cooler temperatures will prove to be a transition to wet snow, with some fluctuations, depending on location.

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"But we are especially focused on the band of heavy wet snow that is likely to develop on the back side of the system," Gillham says, adding that it is still too early to know exactly where that heavy snow will be.

There is still lots of uncertainty with the track of the low and the rain-snow divide. At this point, it appears that dividing line between heavy rain and heavy, wet snow will be in the vicinity of the GTA, with primarily rain south and east of Toronto, including Ottawa and Montreal, and primarily heavy wet snow north and west of Toronto, including London, Kitchener-Waterloo and cottage country.

ON Snow


Minor changes in the storm track will have a major impact on snow totals for the GTA, and will be monitored closely as the system develops over the weekend.

Areas north of the 401 corridor may see snow 5-10 cm, especially the Dundalk and Algonquin Highlands, where 15+ cm could fall.

"In terms of totals, once again, it appears that we will see a wide range in snow totals across the GTA," Gillham says. "Many areas north and west of the GTA could see 10-20 cm of snow with the potential for parts of the region to reach 20-30+ cm."

As we move into the month of December, forecasters are also watching some preliminary signs that show a transition into a more "consistent" and "typical" early winter pattern by the second week of the month.

Be sure to check back as we continue to fine-tune this forecast and potential impactful systems that start out the month of December.