Northern Ontario: Winter Weather Hazards Outlook for Saturday, December 11, 2021

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Forecast Discussion

A deepening low-pressure system out of Colorado will bring a blast of wintery weather to Northeastern Ontario on Saturday. The exact impacts will depend on your location with some areas seeing over 20cm of snowfall accumulation while others see several hours of freezing rain.

We will start to see the first bands associated with this system reach those near Lake Superior during the early morning just after midnight. It likely will start as some wet snow for those near the Georgian Bay shoreline and more sustained snowfall to the north. A thin band of freezing will develop later in the morning stretching from Sault Ste. Marie through Elliot Lake, Sudbury and into Temiskaming Shores. Freezing rain accretion ranging from 2-6mm is possible in this area before it switches over to rain later in the day. Areas around Georgian Bay will quickly transition over to rainfall.

Heavy snowfall will continue through Wawa, Kapuskasing, Chapleau, Timmins and Cochrane with accumulation ranging from 15-25cm by the end of Saturday. Blowing snow may also be an issue with wind gusts reaching 40-60km/h. Stronger gusts near 90-100km/h are possible along the Georgian Bay shoreline. All precipitation will come to an end late Saturday although some drizzle or flurries may continue into early Sunday morning.

Destructive Wind Storm Possible Across Southern Ontario on Saturday With Gusts Up to 90-120 km/h; Risk of Freezing Rain for Ottawa Valley

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A deepening low-pressure system from Colorado will move across Ontario on Saturday bringing with it the threat of potentially damaging to destructive wind gusts to much of Southern Ontario. On the bright side, this system will usher in a brief shot of mild air with temperatures reaching into double digits before a cold front sweeps across the region later in the day putting an end to this. There will also be the threat of freezing rain primarily through the Ottawa Valley and into Northeastern Ontario during the morning hours on Saturday.

We’re expecting the strongest wind gusts to start to pick up around the noon hour with Southwestern Ontario and continue eastward through the afternoon. There is some disagreement amongst the models on the exact strength of these gusts with conservative estimates of around 80-90km/h inland and near 95-100km/h along the shorelines. While more aggressive models point towards what could be the strongest wind storm we’ve seen in years for this region with widespread gusts from 90-105km/h and up to 120km/h for the northeastern shorelines of Lake Ontario and Erie. Regardless of what happens, the winds will be still quite strong and may result in many power outages across Southern Ontario. Be prepared for some wind damage and bring in anything that could be blown away. Secure your holiday decorations!

We have a particular concern for those regions right along the northeastern shoreline on Lake Ontario and Erie due to the very strong southwesterly winds which could gust up to 120km/h. Aside from the potential wind damage, this will likely cause very high waves on the lakes and result in some shoreline flooding. Locations such as Port Dover, Port Colborne and Prince Edward County should be prepared for flooding in areas that have a history of wind-related flooding.

The strong wind gusts will continue into the evening especially for Eastern Ontario. However, we should start to see them die down somewhat later in the evening and as we head into the overnight hours. In addition to the strong wind, we’re also expecting some heavy rainfall with the latest model data pointing to widespread totals between 10-20mm. There is currently a rainfall warning in effect for a wide swath of Southern Ontario, but we’re just not seeing the widespread potential for more than 20mm at this time. In fact, a few models point towards this system underperforming in terms of rainfall with less than 10mm in some areas. Now, there is the risk for some non-severe thunderstorms through Southwestern Ontario and into the Golden Horseshoe which could lead to localized higher rainfall total.

While most of Southern Ontario will see a rapid rise in temperatures overnight and early Saturday morning as a result of some milder air, the same can’t be said for Northeastern Ontario and parts of the Ottawa Valley. It appears that the cold air will be a little more stubborn in this area during the morning which will allow for the risk of freezing rain. It could linger for several hours before the warmer air finally wins over and is able to cause the temperature to rise above the freezing mark.

Ice accretion ranging from 2-6mm can’t be ruled out for locations such as Ottawa, Renfrew, Petawawa, North Bay and Sudbury which could lead to icy road conditions and some power outages. Depending on how fast an existing ice accretion is able to melt, this may add an additional variable to the power outages risk later in the afternoon as the strong wind gusts move in Eastern Ontario. The freezing rain risk will come to an end by the early afternoon hours as it switches over to regular rain.

Northern Ontario: Snowfall Outlook for Saturday, December 11, 2021

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Forecast Discussion

A potential winter storm could bring the threat of freezing rain and heavy snowfall to parts of Northeastern Ontario throughout the day on Saturday. This will also be accompanied by strong wind gusts which may result in blowing snow and raise the power outage risk in areas that see the freezing rain. More details to come in a special forecast to be posted on Friday.

Southern Ontario: Winter Weather Hazards Outlook for Saturday, December 11, 2021

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Forecast Discussion

A strong storm will affect Southern Ontario on Saturday with the main story being potentially damaging wind gusts between 80-115km/h. This could result in some wind damage along with power outages during the day on Saturday. There will also be some heavy rain, however, there is low confidence in exactly how much could fall. More details to come in a full special forecast on Friday.

Southern Ontario: Snowfall Outlook for Friday, December 10, 2021

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Forecast Discussion

Snowfall associated with an Alberta clipper will continue through the early part of Friday for Central and Eastern Ontario. The highest totals ranging from 2-4cm will be found along the Quebec Border and into the Ottawa Valley. Other regions will see just a trace of snow at most. The snow will come to an end quickly after sunrise as the system moves out over Quebec.

Northern Ontario: Snowfall Outlook for Friday, December 10, 2021

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Forecast Discussion

Heavy snowfall continuing from a system that throughout snow to other parts of Northern Ontario could bring up to 10-15cm to parts of Northeastern Ontario during the morning. More details in an outlook to be released Thursday evening.

Southern Ontario: Snowfall Outlook for Friday, December 10, 2021

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Forecast Discussion

Some accumulating snowfall is possible along the Quebec border and into Eastern Ontario during the morning hours on Friday. This is from snowfall that affected Central Ontario late Thursday. We’re expecting around 2-4cm through locations such as Pembroke, Renfrew and Ottawa. More details in a snowfall outlook will be coming Thursday evening.

Southern Ontario: Snowfall Outlook for Thursday, December 9, 2021

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Forecast Discussion

A fast-moving system will bring some accumulating snowfall to parts of Central and Eastern Ontario during the late afternoon and evening on Thursday. General snowfall accumulation ranging from 2-4cm and maybe a few locations seeing up to 6cm is possible. Slightly more accumulation is possible along the northern shoreline of Georgian Bay where lake enhancement will boost totals. Lesser amounts further to the south with some rain mixing in near the Lake Ontario shoreline through the GTA. Eastern Ontario will continue to see snowfall lingering overnight and into Friday morning. This will be covered in a separate outlook for Friday.

Northern Ontario: Winter Weather Hazards Outlook for Thursday, December 9, 2021

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Forecast Discussion

It’s going to be a cold night for those in Extreme Northern Ontario as cold arctic air and a brisk wind makes it feel like -30 to -40°C as you wake up on Thursday. It will moderate somewhat after sunrise. There is also some heavy snow around Lake Superior with accumulation ranging from 12-20cm. See our snowfall outlook for more details.

Northern Ontario: Snowfall Outlook for Thursday, December 9, 2021

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Forecast Discussion

A developing system is expected to slide across Northern Ontario throughout the day on Thursday bringing with it the threat of widespread accumulating snowfall. General amounts from this system won’t be that impressive with around 6-12cm before the end of the day on Thursday. This includes locations such as Sioux Lookout, Armstrong, Fort Hope, Geraldton and Kapuskasing. However, locally higher snowfall totals are expected around the Lake Superior shoreline including Thunder Bay, Marathon and Wawa where some lake enhancement could result in accumulation reaching somewhere around 12-20cm. Blowing snow will also be an issue with 50-70km/h wind gusts particularly during the afternoon hours. Be sure to take your time out on the roads if you’re travelling in the affected regions. The heavy snowfall will affect Northeastern Ontario overnight into Friday morning which will be covered in Friday’s outlook.