Winter Storm Targets Northern Ontario This Week as Intense Snow Squalls Line Up for Southern Ontario Starting Thursday

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A powerful system will sweep through the Great Lakes region this week, bringing a major winter storm to Northern Ontario and setting the stage for a significant snow squall event across Southern Ontario later in the week.

Across Northern Ontario, snowfall will begin to move into regions east of Lake Superior by late Tuesday. Light snow will start from Wawa through Timmins, gradually expanding north and west. Through the overnight hours into Wednesday morning, the system will push into Thunder Bay, Kapuskasing and surrounding communities.

The worst conditions are expected throughout the day on Wednesday. Winds will gust between 40 and 60 km/h, and when combined with heavy snowfall rates, visibility will deteriorate quickly. Blowing snow will be widespread across Northeastern Ontario and conditions may even reach blizzard levels at times.

Treacherous travel conditions will continue into Wednesday night and persist through Thursday morning as the storm deepens. Snowfall intensity will gradually ease later on Thursday, but steady snow will continue as the system stalls over Quebec. This will push long lasting bands of precipitation back into Northeastern Ontario, keeping snow going until early Friday morning.

By the time the storm fully exits, a wide swath of Northeastern Ontario is expected to receive 20 to 50 cm of snow, with localized totals possibly exceeding that. The heaviest totals are expected from Marathon through Kapuskasing, Cochrane, Timmins, and Temiskaming Shores, Wawa, Hearst and Chapleau. Snowfall totals here will range from 30 to 50cm with possibly as much as 60cm in localized pockets.

While Northern Ontario deals with the winter storm, Southern Ontario will be on the warm side of the system on Tuesday and Wednesday. Many areas will flirt with the double digits, especially in Southwestern Ontario. Scattered showers will develop early Tuesday with light rainfall amounts of roughly 5 to 10 mm.

By late Wednesday, though, the pattern begins to shift as cold air wraps in behind the departing system. Temperatures will drop quickly, and any lingering precipitation will change to wet snow by Wednesday evening.

This colder air will set the stage for lake effect snow to fire up. With a westerly wind overnight on Wednesday, snow squalls may begin to develop off Lake Huron and Georgian Bay.

These early bands could bring bursts of heavy snow to Grey Bruce, Parry Sound and Muskoka through Thursday afternoon, although the exact intensity remains uncertain as the higher resolution models are just entering range and showing stronger signals than the medium range guidance.

By late Thursday, winds will shift to a northwest flow. Temperatures will drop further into the negatives and this will allow squalls to strengthen. The Georgian Bay band is expected to sink south into Simcoe County and then extend into Kawartha Lakes and Peterborough.

At the same time, the Lake Huron band will slide south into Huron County and stretch toward Kitchener and the western GTA. Some early guidance even hints that this band could link up with the flow off Lake Superior, which can enhance snowfall rates.

Heading into Friday, it is still too early to give precise band placement. Current thinking suggests the northwest flow will hold through much of the day before winds start easing over the weekend. If that happens, squalls could remain active for an extended period.

While details can still shift, we are beginning to narrow down regions with the highest risk of heavy snowfall starting Thursday morning and continuing into Friday evening. Squalls will shift around at times, so snowfall will not be constant, but those under the core of the bands could see snowfall rates approaching 5 to 10 cm per hour. It will not take long for the snow to accumulate.

At this stage, exact totals are not possible to predict for Southern Ontario. However, some regions could easily see 25 to 50 cm by Friday night, with the potential for higher localized totals once high-resolution data comes into range.

For Lake Huron, our current focus areas include Kincardine, Goderich, Hanover, Kitchener, Hamilton and Orangeville.

For Georgian Bay, our primary targets include Midland, Barrie, Gravenhurst, Bracebridge, Orillia, Kawartha Lakes and Peterborough.

Anyone living in or near these regions should be prepared for dangerous travel conditions beginning Thursday. School bus cancellations are likely for some regions, and road closures are possible if squalls remain intense or stationary.

Rare November Stratospheric Warming Event Could Spread Arctic Chill Across Canada for December

You may have heard a new term being thrown around in the news and on social media: “Sudden Stratospheric Warming”. It’s not a new term, meteorologically speaking, and it’s related to the polar vortex. It happens most winters, but it’s making headlines now because of how early it is happening; it has only occurred three times in the month of November over the last 70 years. Additionally, this could be the earliest instance of sudden stratospheric warming on record and it could lead to some very cold temperatures across the country in the coming weeks.

It’s certainly nothing we can’t handle, but it’s always interesting to learn about how something happening in the Arctic, 10s of kilometres above the surface, can impact our day-to-day weather.

Before we dive into what sudden stratospheric warming is, however, we’re going to need a bit of background information. The first thing we need to know is what and where the stratosphere is.

The layers of the atmosphere. Image courtesy of NOAA.

The Earth’s atmosphere is made up of layers and the stratosphere is the second layer from the surface, stretching from 10-50km above the surface. It sits on top of the troposphere, which is where we live and all our weather occurs. The two layers are separated by the tropopause, where the temperature stops decreasing with height and it instead stabilizes. Moving higher, into the stratosphere, the temperature increases with height and the layer itself is quite stable, making it ideal for commercial planes to fly in.

Next, we need a bit of understanding of the polar vortex. This is a concept that has become more mainstream in the last 10 years or so, but there’s a bit more to it than just a period of cold weather.

The easiest way to explain the polar vortex is to imagine a spinning wall of wind, called the polar night jet, in the stratosphere that traps cold air over the Arctic. The polar vortex is always there, but it is weaker in the summer and stronger in the winter during polar night, which is how the polar night jet gets its name.

A stable polar vortex vs a disrupted polar vortex. Image courtesy of NOAA.

When the polar vortex is stable, it can be almost perfectly circular and centred over the North Pole, while the polar jet stream in the troposphere stays further north and flows west to east. However, the polar vortex can be disrupted and the circulation weakened, allowing cold air to flood southwards and pushing the polar jet stream further south and making it become wavy.

One of the main ways the polar vortex can be disrupted is through a sudden stratospheric warming event. As the name suggests, sudden stratospheric warming is when we see sudden warming in the stratosphere, particularly over the polar regions. This could be upwards of 40°C of warming over the course of only a few days!

Sudden stratospheric warming is typically caused by strong upper level high pressure that interacts with the low pressure polar vortex. The high pressure pushes the polar vortex away from the North Pole, settles there in its place and blocks out the polar vortex. Air always falls within a high so once the high pressure replaces the polar vortex, the air in the stratosphere collapses, warming as it falls due to compressional heating and resulting in the sudden stratospheric warming.

Meanwhile, the polar vortex has become weakened and disrupted, forcing the polar jet stream to become wavy and the polar night jet slows down or even reverses direction. This all results in cold air flooding the mid-latitudes throughout the Northern Hemisphere until the blocking high weakens and the polar vortex can restrengthen, allowing it to move back to over the North Pole.

The modelled presence of a high over the north pole (shown in Yellow, red and Pink)and the polar vortex at lower lower latitudes (shown in blue, purple in green) on November 23rd. image courtesy of WeatherBell.

Weather models are showing that we could see the beginnings of a sudden stratospheric warming event starting in the coming days and temperatures in the stratosphere could jump to 30°c above normal. This means that there could be an outbreak of cold Arctic air in the next two weeks or so.

How long this cold air outbreak lasts is dependent on the strength of the sudden stratospheric warming event. If the incoming high pressure is disruptive enough for the winds of the polar night jet to reverse, the Arctic air could persist over the country for several weeks. Two of the previous three instances of sudden stratospheric warming in November saw this wind reversal and in those years, the cold lasted throughout the month of December.

The GFS Model of temperature anomalies (departures from normal) on the morning of November 30th. Image courtesy of WeatherBell.

It’s important to note that there is still some uncertainty in how all of the pieces will come together for this possible sudden stratospheric warming event and there’s a slight possibility that it doesn’t even happen. However, it’s becoming increasingly likely that we will see a disruption in the polar vortex so it becomes a question of who gets the cold, how cold it gets, and for how long.

The American GFS model, for instance, shows the Arctic air arriving in British Columbia and Alberta by mid-next week and spreading eastward in the following days. By Sunday morning, much of the country could see temperatures well below seasonal and some areas could see temperatures of 20°C below normal.

As we get closer to the sudden stratospheric warming taking place, we will have a clearer look at how long the Arctic air could be around. Until then, now might be a good time to dig out all your winter gear because you might need it!

Snow Squalls Take Aim at London, Barrie and Northern GTA on Sunday With Up to 25-50cm of Snow Possible

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We enjoyed a brief break from the wintry weather on Saturday as temperatures soared into the double digits across much of Southern Ontario. The exception was Eastern Ontario, where the Ottawa Valley dealt with hours of freezing rain.

But that warm spell is going to be short-lived. Cooler air returns overnight into Sunday, and temperatures will slide back below the freezing mark. Once that happens, the lake effect snow machine will fire up again for the next couple of days.

And no, it isn’t déjà vu. The target zone for this round of squalls will look very similar to last week’s event, but the focus shifts slightly east. That puts areas like London, Barrie and even the Northern GTA, including York Region, in line to be hit hard.

By the time the squalls wind down on Monday, the hardest hit spots could be digging out from more than 25cm, with the potential for very localized pockets of 50cm.

PRECIP TYPE - MAP FROM WEATHERBELL

We expect the snow squall activity to begin ramping up late Sunday morning. As temperatures fall, lake effect rain bands will flip over to snow off the southeast shoreline of Lake Huron and Georgian Bay.

While the changeover happens in the morning, ground temperatures may stay just above freezing for several hours. This means the first few hours of snow could melt on contact. Accumulation will start later in the day once temperatures reach the freezing mark.

Even before the snow begins to stick, visibility will drop quickly. Those in the affected areas should expect sudden whiteouts and dangerous driving conditions.

Hourly snowfall rate (cm) - MAP FROM WEATHERBELL

By the dinner hour, the squalls will become much more organized. Snowfall rates from the Lake Huron band could rise to 5cm per hour. This main band is expected to extend from Lake Huron through Goderich and southern Huron County into the London region.

Additional squall activity will form southeast of Georgian Bay, running from the shoreline through Barrie and Angus and into Newmarket and Durham. This band looks weaker than the Lake Huron squall at first, but could still deliver rates of 2 to 4cm per hour.

Hourly snowfall rate (cm) - MAP FROM WEATHERBELL

The worst conditions are likely around midnight. The Lake Huron band is expected to lock onto London, bringing intense snow and rapid accumulation of 6 to 8cm per hour.

The Georgian Bay squall will also strengthen, sliding south of Barrie and focusing on Angus, Bradford and Newmarket. Some signals show it reaching into the Eastern GTA, including Scarborough, Ajax and Oshawa.

These squalls should remain mostly stationary overnight, although minor drifting is possible. As temperatures fall several degrees below freezing, expect snow to pile up quickly.

Hourly snowfall rate (cm) - MAP FROM WEATHERBELL

By mid-morning Monday, the bands will begin to weaken as winds shift more westerly. Some lake effect flurries could linger east of Lake Huron into Grey Bruce, but they are not expected to be very organized. Everything should taper off by late Monday.

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Snow squall forecasting always comes with big caveats. The bands are extremely narrow, which means the difference between 50cm and almost nothing can be only a few dozen kilometres.

This is why we provide a broad range. They help capture that uncertainty, but they are not a guarantee. With this event, the bands appear very intense but also very narrow, which means gradients will be sharp.

Based on the latest data, we expect the hardest hit areas from the Lake Huron squall to include Goderich, Clinton, Lucan, Exeter, Mitchell and London. Snowfall totals here could range from 25 to 50cm, with the chance that someone ends up over 50cm in a very localized spot.

Surrounding regions, including Grand Bend, Tillsonburg, Stratford, Wingham, and Point Clark, could see 15 to 25cm.

Further east into Grey Bruce and Dufferin County, we are expecting 5 to 15cm mainly on Monday as the lake effect shifts northward.

The Georgian Bay band looks even narrower than the Lake Huron band. A small corridor stretching from Collingwood through Angus and into Innisfil could see 25 to 35cm, with a chance of 50cm if the band really intensifies.

The City of Barrie is right on the edge. A small shift north or south would bring very different results. For now, the highest totals look likely in the south end of the city with 15 to 30cm. The north end may be closer to 10 to 20cm.

Substantial totals may also extend into the Northern GTA, including Bradford, Newmarket and Aurora. Totals along the Highway 400 and 404 corridor could range from 15 to 30cm.

Across the east end of Toronto and Durham, including Ajax, Pickering and Oshawa, occasional heavy bursts may bring 5 to 10cm.

The rest of Southern Ontario should see less than 5cm of snow by Monday from the lake effect.

All the Seasons in One Weekend for Southern Ontario as Freezing Rain, Thunderstorms and Snow Squalls Line Up

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There is really only one way to describe what November has been like across Southern Ontario when it comes to the weather: a roller coaster.

Last weekend brought our first widespread snowfall event of the season. That was quickly followed by intense snow squalls that buried parts of the Lake Huron shoreline with more than 50 cm of snow early this week.

That seasonal whiplash continues this weekend as a clear battle sets up between cold, wintery air and much milder fall-like conditions. Eastern Ontario, especially around the Ottawa Valley, will stay on the cold side with a risk of prolonged freezing rain throughout the day on Saturday.

Southwestern Ontario and the Golden Horseshoe will see a completely different story. Temperatures are set to rise into the double digits, and there is even a risk of thunderstorms on Saturday. Some of the warmest pockets around Windsor could briefly flirt with the 20s for a few hours.

By late Saturday, a sharp cold front will sweep through the region. This will send temperatures plunging again heading into Sunday, settling the battle in favour of the colder air. As this cold push arrives, the lake effect snow machine is expected to roar back to life over both Georgian Bay and Lake Huron.

TEMPERATURE - MAP FROM WEATHERBELL

We expect a frosty start to Saturday morning for most of Southern Ontario. Deep Southwestern Ontario will be the main exception as milder air starts to slide in early. Most areas should wake up close to the freezing mark. Deep Southwestern Ontario will already be climbing through the mid single digits.

By noon, Deep Southwestern Ontario should reach the double digits. Further northeast into the rest of Southwestern Ontario, the Golden Horseshoe and parts of Central Ontario, temperatures will range from the low to mid single digits. The Ottawa Valley will remain near the freezing mark well into the afternoon as the surge of mild air stalls just to the southwest.

PRECIP TYPE - MAP FROM WEATHERBELL

A developing system will start to spread heavy precipitation into Southern Ontario late Saturday morning or early afternoon. For most areas, temperatures will be warm enough for rain to be the dominant precipitation type. There’s even the risk of a thunderstorm!

Over the Ottawa Valley, however, we expect patchy freezing rain to form as temperatures linger stubbornly near the freezing mark.

Model guidance is not fully aligned on how warm the air will get in that region. Even a small shift of one or two degrees will change how long the freezing rain lasts and how much ice is able to accrete. This is one of the key uncertainties for Saturday.

TEMPERATURE - MAP FROM WEATHERBELL

Through Saturday evening, temperatures will continue climbing across much of Southwestern Ontario. Cities like London, Kitchener and Hamilton are expected to reach the double digits.

One important note is that daytime highs in many areas will actually be reached late in the evening instead of during the normal warmest part of the day!

Meanwhile, that pocket of near-freezing air over the Ottawa Valley is expected to hold on into the evening, which could allow several more hours of freezing rain.

As the system pulls east overnight Saturday, colder air will sweep in behind it. Temperatures will tumble through Sunday morning, switching any lingering precipitation to wet flurries by the time you wake up.

Hourly snowfall rate (cm) - MAP FROM WEATHERBELL

Behind the front, bands of lake effect snow will begin developing off Lake Huron and Georgian Bay early Sunday. These bands look messy and disorganized through much of the day, although localized totals of 10 to 20 cm are possible.

By late Sunday, more focused and intense squalls could form, especially around the London region off Lake Huron. These squalls may continue into Monday and could lead to localized 20+ cm totals.

We will have a more detailed, dedicated lake effect forecast released soon.

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When it comes to freezing rain accretion, there are several variables that could reduce or increase the amount of ice that actually builds up. This is a very temperature-sensitive event.

The heaviest icing is expected directly along the Quebec border and into the Hawkesbury region. Models show the potential for over 10 mm of freezing rain, but it is unclear how much of that will be able to stick. Heavy precipitation rates could limit the amount of ice that accumulates, and temperatures will sit very close to the freezing mark for much of the event.

Given all of this, we are going with a general 5 to 10 mm of icing for the hardest hit areas. If temperatures are even slightly warmer than expected, accretion could end up lower. This is certainly enough to lead to localized power outages and icy roads.

For the City of Ottawa, they sit right on the dividing line between lighter icing and heavy icing. We have placed them in the 2 to 5 mm range, but they could see locally up to 7 mm if the cold air becomes more stubborn than currently forecast.

Outside of the Ottawa Valley, expect minimal icing. Areas such as Bancroft, Cloyne, Perth, Carleton Place and Cornwall may see an hour or two of freezing rain before changing over to rain.

Snow Squalls Could Bury Parts of Southern Ontario’s Snowbelt in Up to 50cm of Snow Early This Week

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As much of Southern Ontario cleans up after our first widespread snowfall of the season, Mother Nature is showing no signs of slowing down. The lake effect snow machine is roaring to life over Lake Huron and Georgian Bay as we kick off the second week of November.

Snow squalls have already developed south of Lake Huron late Sunday evening and are expected to strengthen through the night. We’re also anticipating some squall development along the southern shoreline of Georgian Bay, which should organize by Monday afternoon or evening.

Two main regions are likely to see the most intense activity. The first stretches between Sarnia and London, while the second includes areas south of Georgian Bay from Blue Mountain and Meaford toward the west of Barrie. Both zones could see heavy snow squalls lasting through to Tuesday morning.

While snowfall totals will vary significantly across short distances, confidence is increasing that the hardest hit areas could see as much as 25 to 50cm by the time the squalls taper off on Tuesday. Localized pockets may even exceed 50cm, depending on where the heaviest bands set up.

Road conditions are expected to deteriorate quickly in these regions, with road and highway closures likely late Monday and into early Tuesday when the most intense squalls occur. Travel should be avoided unless absolutely necessary, as these bands can produce sudden whiteouts, making it nearly impossible to see the road ahead.

ESTIMATED AIR TEMPS AROUND 1.5KM ABOVE GROUND - MAP FROM WEATHERBELL

This setup is being fueled by a rare November appearance of a mini “Polar Vortex” which is pulling a blast of Arctic air into Southern Ontario. This cold air is flooding the upper levels of the atmosphere and setting the stage for intense lake effect activity.

To put it simply, when forecasters talk about 850mb temperatures, we’re referring to the air temperature roughly 1.5 kilometres above the ground. This level helps forecasters understand how cold the air mass is higher up in the atmosphere, which is critical for predicting lake effect snow.

Over the next few days, 850mb temperatures are expected to plunge into the negative teens. Lake effect snow forms when there’s a large temperature difference between the lake surface and the air above it, generally 13°C or greater. With upper air temperatures between -10°C and -15°C and lake temperatures still above 10°C, that difference is more than 20°C, creating ideal conditions for lake effect snow to thrive.

hourly snowfall rates (cm) - MAP FROM WEATHERBELL

As of midnight, snow has already developed off the southern shores of Lake Huron, impacting the Sarnia region. So far, the bands have been disorganized and spread out, but that’s expected to change by late Monday morning as a stronger, more focused squall forms somewhere between London and Sarnia.

While the exact placement remains uncertain, areas near Petrolia and Strathroy appear most likely to be in the direct path. The band will likely shift through the day as wind directions fluctuate, leading to varying snow intensities across nearby towns.

hourly snowfall rates (cm) - MAP FROM WEATHERBELL

By Monday evening, things will really start to ramp up. The main squall off Lake Huron will likely push inland, with a more northwesterly wind direction steering it toward Grand Bend, Goderich and potentially the western edges of London. It’s still unclear if the squall will reach directly into London or remain just outside the city, but if it does, the heaviest snowfall will likely fall on the west side.

Meanwhile, snow squalls are expected to organize over Georgian Bay with heavy snow bands developing between Owen Sound and Barrie. There’s still some disagreement among models, with some focusing more on Wasaga Beach and Barrie while others favour a southern shoreline setup.

An interesting twist could occur if these Georgian Bay bands extend far enough inland to be enhanced by Lake Ontario. In that case, snow could reach into the western GTA and even the Niagara region, leading to sudden bursts of heavy snow if everything aligns.

hourly snowfall rates (cm) - MAP FROM WEATHERBELL

This lake effect activity is expected to persist overnight and into Tuesday morning, though the Georgian Bay bands should weaken slightly around sunrise. West of London, however, heavy snow could continue well into Tuesday morning before breaking apart as conditions become less favourable later in the day.

As always with lake effect snow, totals are extremely difficult to pinpoint. These narrow bands can stay locked over one community for hours while completely missing another just a few kilometres away. One person may end up shovelling half a metre of snow while someone nearby barely sees a dusting.

That said, two areas consistently stand out across the latest model runs. One includes Lambton Shores, Grand Bend and Strathroy, while the other covers the southern Georgian Bay shoreline and higher terrain around Blue Mountain. These regions could see totals ranging from 25 to 50cm by Tuesday.

Surrounding communities such as Petrolia, Thamesville, St. Thomas and Lucan, along with Orangeville, Shelburne and Flesherton, are more likely to see 15 to 25cm.

Both London and Barrie sit right on the edge between lighter and heavier accumulations. We currently have them in the 5 to 15cm or 15 to 25cm zones, depending on how far east the snow squalls extend.

Finally, the Niagara region remains uncertain. If the Georgian Bay squalls stretch far enough inland and connect with Lake Ontario, parts of the region could pick up over 15cm of additional snow.

Outside of these snowbelt regions, impacts will be much less significant. A few flurries and brief bursts of snow are possible as the squalls wobble, but most areas outside the direct lake effect zones should remain relatively calm through Tuesday.

Snowy Sunday Sweeps Into Southern Ontario With First Widespread Snowfall of the Season

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While there has been a lot of uncertainty surrounding Southern Ontario’s first widespread snowfall event of the season, we’re finally starting to get a clearer picture of what will unfold on Sunday. After several model shifts over the past few days, the latest data is now coming into better alignment, giving us a more confident idea of how this system will behave.

A developing low-pressure system is expected to move in from the southwest late Saturday night, tracking across areas near Lake Erie through the day on Sunday. As it does, it will bring a broad swath of snow stretching from Windsor through the Golden Horseshoe and into Eastern Ontario. Snow is expected to last much of the day before gradually tapering off overnight.

At this stage, snowfall totals are expected to vary quite a bit across the region. The exact placement of the heaviest snow bands remains uncertain, and surface conditions will also play a big role. Since the ground is still relatively warm, some of the early snowfall may melt on contact before it can begin to accumulate, especially on roads and sidewalks.

In general, by Monday morning, snowfall totals are expected to range from around 5 to 10 cm across the Golden Horseshoe and into Eastern Ontario. Within those areas, localized pockets, particularly in Eastern Ontario, could pick up as much as 15 to 20 cm according to the latest model runs. Further north and west, across Central and Southwestern Ontario, amounts will be lower with less than 5 cm expected in most spots.

As the system departs, colder air will pour into Southern Ontario late Sunday night, sending temperatures well below freezing. Any slushy snow or water on roads, sidewalks, and driveways will freeze quickly overnight, which could create slick conditions for the Monday morning commute. Drivers should be prepared for icy patches, and there’s a decent chance of school bus cancellations in areas that see higher snowfall totals.

The colder air will also fire up the lake effect snow machine early next week. Model guidance suggests that an intense but narrow band of snow could form southeast of Lake Huron late Monday and continue into Tuesday. This could impact communities such as Grand Bend and London, where local snowfall totals could exceed 25 cm if the band remains stationary for an extended period.

PRECIP TYPE - MAP FROM WEATHERBELL

For timing, snow is expected to begin in Deep Southwestern Ontario shortly after midnight. Around Windsor and Chatham, it may even start as rain before transitioning to snow as temperatures drop closer to dawn.

PRECIP TYPE - MAP FROM WEATHERBELL

By late Sunday morning, the snow will have spread into the Golden Horseshoe, becoming heavier through the afternoon. In Eastern Ontario, snow will likely begin around Kingston early in the morning and reach the Ottawa area by midday.

hourly snowfall rates (cm) - MAP FROM WEATHERBELL

The heaviest snowfall rates across the Golden Horseshoe are expected from early to mid-afternoon, with some models projecting bursts of 2 to 4 cm per hour at times before tapering off toward the evening.

PRECIP TYPE - MAP FROM WEATHERBELL

For Eastern Ontario, steady snow will continue through the afternoon, peaking after dinner before easing into scattered flurries overnight. With that timing, school bus cancellations are quite possible for parts of Eastern Ontario on Monday.

There are also some indications that freezing rain or ice pellets may mix in along the international border Sunday evening. Areas such as Kingston, Brockville, and Cornwall are most at risk for this brief mix, which could add an extra layer of slickness to untreated surfaces.

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While there is still some disagreement among the models on exactly where the heaviest snow will fall, the general expectation remains 5 to 10 cm along the Golden Horseshoe and into Eastern Ontario, with some locally higher amounts near 15 cm.

We’ve outlined portions of Eastern Ontario and the higher elevations of the Niagara region on our map with a dotted zone, representing areas that could overachieve and see closer to 20 cm. However, that outcome is far from certain.

Keep in mind that this is the first significant snowfall of the season, and with ground temperatures still above freezing, actual accumulation could vary from one street to the next. Some areas may see a quick coating, while others struggle to hold the snow through the day, especially near the lakeshores.

Elsewhere, Southwestern Ontario and much of Central Ontario should see lighter amounts, generally only a few centimetres, with some localized areas possibly reaching up to 8 cm. Regions like Grey-Bruce and the northern parts of Central Ontario will likely miss out on the heaviest snow this time, but that may not last long as lake effect activity ramps up early next week.

PRECIP TYPE - MAP FROM WEATHERBELL

As higher-resolution models continue to come into range, we’re getting a clearer idea of what the first snow squall event of the season could look like. Current projections suggest activity will develop on Monday, with a more organized squall forming by the evening.

This band may set up somewhere between Grand Bend and Kettle Point, extending inland, likely just west of the City of London. Additional bands may also develop off Georgian Bay, impacting areas around Meaford and Collingwood.

Communities caught under these narrow squalls could see impressive snowfall totals, while just a few kilometers away, grass may still be visible. We’ll continue to refine the details as the event approaches and will have a more specific forecast on who could see the most snow closer to Monday.

Overall, this marks the true start of the winter season across Southern Ontario, with several systems and lake effect events lining up behind this one. It’s a good time to check that your winter tires are ready, snow shovels are handy, and morning routines include a few extra minutes to clear off your car. Winter is here to stay.

Southern Ontario to Plunge Into Winter as Sunday Snowstorm Could Dump Up to 20 cm of Snow

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It feels like just yesterday we were talking about record-breaking heat that stretched well into October. But November has been a completely different story, with winter now making its presence known across Southern Ontario. Those warm late-autumn days are coming back to haunt us, as the still-warm lakes are setting the stage for a series of snowy chances in the days ahead, including the lake effect snow machine coming to life.

Cold Arctic air is set to flood into the province, bringing several snowmakers with it, including a potential snowstorm on Sunday, followed by intense snow squalls early next week.

Our first system arrives on Friday, spreading across Ontario throughout the day. Southern Ontario will mainly see rain from this one, while Northern Ontario braces for a significant dumping of snow. Some areas could see close to 20 cm by Saturday.

As colder air rushes in behind this system, temperatures will plunge across Southern Ontario through Saturday night. By Sunday, much of the region will be below freezing, setting the stage for the next system expected to move in during the day Sunday. Early indications suggest that parts of Southern Ontario could see significant snowfall from this system, with totals possibly reaching up to 20 cm by Sunday night.

That said, there’s still plenty of uncertainty surrounding the exact track of the storm. A slightly more southern route could pull the heaviest snow into the Greater Toronto Area as colder air dips farther south.

PRECIP TYPE - MAP FROM WEATHERBELL

The first round of precipitation will begin in Northwestern Ontario late Thursday, spreading across Northeastern and Southern Ontario by Friday morning.

RAINFALL TOTALS - MAP FROM WEATHERBELL

For most of Southern Ontario, this will mean a steady rainfall, with totals around 5 to 10 mm, although localized pockets near the lakes could see closer to 15 mm.

SNOWFALL TOTALS - MAP FROM WEATHERBELL

Higher elevations in Central Ontario, including Algonquin Park, could see some wet flurries mix in at times. Farther north, around Hearst, Kapuskasing, Cochrane, and Timmins, it’s all snow, with totals of 15 to 20 cm possible by Saturday morning.

TEMPS - MAP FROM WEATHERBELL

Behind the system, much colder air will spill into Central Ontario overnight Friday into Saturday, dropping temperatures well below freezing. The rest of Southern Ontario will see the chill arrive soon after, with most regions seeing their daytime highs recorded just after midnight Saturday before temperatures tumble through the day.

TEMPS - MAP FROM WEATHERBELL

By early Sunday morning, the cold will be firmly in place. Most areas will be below freezing, except for parts of Deep Southwestern Ontario and along the Lake Ontario shoreline where temperatures will hover just above zero.

PRECIP TYPE - MAP FROM WEATHERBELL

This cold setup will pave the way for Sunday’s incoming system. Models are in disagreement about the storm’s path, which will ultimately decide who gets the heaviest snow. The American and Canadian models track the low across Lake Erie and Lake Ontario, placing the rain-snow line near the GTA.

In this scenario, areas north of the GTA, including parts of Southwestern Ontario, Lake Simcoe, and the Ottawa Valley, would see heavy snow, while the GTA experiences a mix of rain, ice pellets, and wet snow.

PRECIP TYPE - MAP FROM WEATHERBELL

Even a small shift southward, as suggested by the European model, would change everything. That track takes the low through Pennsylvania and Upstate New York, shifting the heaviest snowfall into the GTA and surrounding regions, with totals over 15 cm.

SNOWFALL TOTALS - MAP FROM WEATHERBELL

In this case, the snow would stretch from London through the GTA, Peterborough, and into Ottawa, while Central Ontario and Grey-Bruce see lower amounts.

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For now, most models favour the northern track, so that’s what we’re leaning toward in our preliminary forecast. But if the European solution proves right, those snowfall zones could shift south before the final forecast is issued.

Under the current setup, the heaviest snow is expected across a broad stretch of Southwestern Ontario, including the Lake Huron shoreline through Kitchener and up toward Barrie, Lindsay, and Peterborough, extending into the Ottawa Valley. These areas could see 10 to 15 cm of snow, with localized pockets near 20 cm possible.

The American NAM model is even more aggressive, suggesting up to 30 cm in some areas, though that’s likely overdone. The London area, GTA, and Eastern Ontario fall into a mixing zone, with 5 to 10 cm possible once precipitation switches to snow. Should the system shift farther south, those totals could increase.

Farther south, places like Windsor, Chatham, Sarnia, and the Niagara Region are expected to stay mostly rain, though a slushy 5 cm of snow is possible.

Snowfall will taper off by late Sunday, but the story won’t end there. Behind the storm, a strong surge of cold air over the still-warm Great Lakes will ignite a burst of lake-effect snow squalls on Monday.

The exact regions that will see the most intense squalls remain uncertain until higher-resolution models come into range, but areas downwind of Lake Huron and Georgian Bay should prepare for the potential of significant accumulations. Some communities could be digging out from 25 cm or more by early next week.

Snowy Scare: Frightful Flurries May Haunt Parts of Southern Ontario on Halloween Night

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After a soggy start to Halloween Eve across Southern Ontario on Thursday, a strong system will cast a gloomy spell over the region with widespread rainfall. But don’t be fooled, as that’s only a taste of what Mother Nature has brewing in her cauldron for Halloween itself.

Last year, we were treated to a mild and friendly Halloween with temperatures that felt more like a trick than a treat. This year, however, it looks like Halloween will send a real shiver down your spine as temperatures drop to levels more fitting for the undead.

Rain from Thursday is expected to linger overnight and into the early hours of Friday, heavy at times, especially across Eastern Ontario. The good news is that the worst of the rainfall should clear out just in time for trick-or-treating across Southwestern Ontario and the Golden Horseshoe. Temperatures will hover around what’s normal for this time of year, ranging from the mid to upper single digits, possibly reaching the low double digits in Deep Southwestern Ontario.

But it’s as if a witch has placed a chilling curse over Central and Eastern Ontario. As the rain lingers through Friday, some areas could begin to see strange white shapes drifting through the sky and no, they aren’t ghosts! These spooky apparitions are far more real, as rain could turn to wet flurries as early as Friday afternoon. Cold air will creep in like a Halloween fog, sending temperatures tumbling toward the freezing mark by evening.

While there’s some disagreement between models (a classic case of meteorological mischief), there’s solid agreement that a wide stretch of Central Ontario may experience at least a few wet flurries on Halloween night.

Where the models differ is in timing and intensity. Some are quite aggressive, conjuring an earlier and more widespread switchover to snow that could even allow for light accumulations in higher elevations. Others show a less frightful outcome, with flurries limited to the hills and highlands later in the day as the rain fizzles out elsewhere.

PRECIP TYPE - MAP FROM WEATHERBELL

As we rise on Halloween morning, rain will still be haunting much of Southern Ontario, though it will begin to taper off from west to east.

That’s where the great model split begins. For this forecast, we’re focusing on the NAM (American) and HRDPS (Canadian) models, which represent two distinct camps. The European model seems to be siding with the Canadian solution.

The American model pulls colder air into Central Ontario faster, dropping temperatures a few degrees lower than the Canadian model. It might not sound like much, but when temperatures hover near freezing, every degree counts. This could allow snow to start mixing in by early afternoon.

Areas like Algonquin Park, Haliburton, Bancroft, and northern Muskoka may see the first flurries, with the “mixing zone” spreading south through the afternoon into Muskoka, northern Simcoe County, and the Kawartha Lakes region.

PRECIP TYPE - MAP FROM WEATHERBELL

The Canadian model delays the switchover until closer to dinnertime, mainly over higher elevations.

By then, the precipitation in western areas may already be fading, keeping Muskoka and Simcoe County mostly rain-soaked rather than snow-covered.

PRECIP TYPE - MAP FROM WEATHERBELL

If the American model’s spookier version plays out, several hours of heavy, wet snow could fall Friday evening. While the ground is still warm, we’ve seen before that a strong enough burst of snow can briefly overcome that warmth and start to accumulate.

This model also spreads the snowy risk zone further east, even hinting at flakes creeping into the Ottawa Valley.

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The most likely areas to see actual snow include the higher elevations of Central Ontario, such as Sundridge, Huntsville, Algonquin Park, and Bancroft. These regions could even pick up a few slushy centimetres by night’s end if the stronger scenario comes true.

Elsewhere across Central Ontario, including Parry Sound, Bracebridge, Orillia, Kawartha Lakes, Tweed, and Pembroke, some wet flakes could mix in as trick-or-treaters prowl the streets. Accumulation isn’t expected here as the ground remains too warm, but it might add an extra eerie touch to the evening.

ESTIMATED PRECIP OVER LAST 3 HOURS - MAP FROM WEATHERBELL

As the ghosts, goblins, and ghouls hit the streets after nightfall, Southwestern Ontario will enjoy the calmest conditions, with rain clearing out hours earlier.

Central and Eastern Ontario, however, may not be as lucky. Light rain or even a few flurries could continue into the early evening, adding some spooky atmosphere to the night.

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For the prime trick-or-treating hours, Deep Southwestern Ontario will be the mildest, with temperatures around 8 to 12°C at 8 PM. Elsewhere across the Golden Horseshoe and Eastern Ontario, temperatures will settle into the mid to upper single digits.

The chilliest readings will haunt Central Ontario, where places like Muskoka, Algonquin Park, and Bancroft may see readings near the freezing mark with flakes swirling through the air. Those heading out should make sure their costumes have a few extra layers because this Halloween, it’s not just the monsters giving people chills.

Have a Happy Halloween!

Southern Ontario Turns Chilly With a Chance of Early Season Flurries for Some Areas Friday Morning

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The feeling of change is definitely in the air across Southern Ontario this week. Fall colours are now past their peak in many areas, and a noticeable chill has taken hold across the region. The arrival of cooler air, combined with the still-warm Great Lakes, has kicked off another round of lake-effect precipitation off Lakes Erie, Ontario and Huron.

While it’s still warm enough to keep most of that precipitation as rain, the traditional “snow belt” east of Lake Huron and Georgian Bay will continue to see periods of lake-effect rain through Thursday and into Friday. Local rainfall totals of 25 to 50 mm are possible by Friday, especially east of Lake Huron.

However, not everyone will escape a touch of wintry weather this week. The latest model data suggests that temperatures could dip close to the freezing mark across parts of Central Ontario late Thursday night into early Friday morning. With some lingering showers still moving through the region, a few areas could see those showers briefly mix with wet flurries before sunrise on Friday.

The best chance to spot the first flakes of the season will be across Northern Muskoka (including Huntsville and Sundridge), Algonquin Park, Bancroft and North Bay. That said, precipitation will be very scattered, and not all of these locations will see snow. Even if flakes do fall, they won’t stick around for long as the ground remains too warm and temperatures will quickly climb above freezing later in the morning.

ESTIMATED TOTAL RAINFALL BY FRIDAY - MAP FROM WEATHERBELL

For those near Lake Huron and Georgian Bay, Thursday looks to be a wet one. Bands of lake-effect rain are expected to develop overnight Wednesday and linger through the day Thursday. As is typical with lake-effect events, rainfall totals will vary greatly over short distances depending on where the bands set up.

These bands are expected to wobble around through Thursday into Friday, spreading precipitation over a broader area rather than locking in on one spot. If one of the stronger bands does remain stationary for an extended time, localized flooding could occur, particularly near Kincardine and Goderich where some models show up to 50 mm of rainfall possible by Friday.

The lake-effect setup off Georgian Bay isn’t expected to be quite as strong, but parts of Simcoe County around Collingwood, Wasaga Beach and Barrie could still see locally up to 25 to 50 mm of rain. Again, the highest amounts will be very localized.

Elsewhere across Southern Ontario, expect occasional showers Thursday with generally less than 10 mm of rain as the heaviest precipitation remains confined to areas near the lakeshores.

By Friday morning, precipitation will gradually taper off as conditions become less favourable for lake-effect activity.

ESTIMATED AIR TEMPERATURE on friday morning - MAP FROM WEATHERBELL

Overnight Thursday into Friday, temperatures will drop into the low single digits across much of Southern Ontario, with some Central Ontario communities dipping to near or just below freezing.

PRECIP TYPE - MAP FROM WEATHERBELL

While it’s not the first time this fall that temperatures have touched the freezing mark, what’s different this time is that lingering precipitation from both the lake-effect activity and a system over Quebec could overlap with those cold temperatures.

If any precipitation develops overnight, it could easily fall as wet flurries given the near-freezing surface temperatures and even colder air aloft that would favour snow instead of rain.

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It’s worth noting that models disagree on how much precipitation will actually be present on Friday morning. Some may be underestimating light, scattered precipitation, which means there’s a chance flakes could be seen as far south as Huntsville and Bancroft. The most likely region for these flurries remains around North Bay and Algonquin Park, where multiple models consistently show light snow.

Unless you’re up early Friday morning, you’ll likely miss the brief appearance of the season’s first flakes. Any snow that does fall will melt quickly once temperatures climb above freezing, and no travel impacts are expected.

Severe Thunderstorms Possible for Manitoba Thursday, But Risk Remains Questionable

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The southern half of Manitoba, particularly in the southeast, could see some severe thunderstorms today when a cold front tracks through the region. However, in typical Manitoba fashion, whether storms end up even developing today is very questionable.

The cold front will begin to move through Southern Manitoba early this afternoon and it should reach the Winnipeg area around the late afternoon or early evening hours. Normally, a cold front is more than enough to trigger severe thunderstorms, but the issue is that there is expected to be a significant amount of capping in the atmosphere today, which would greatly inhibit thunderstorm development.

Due to this capping, there is considerable disagreement between weather models regarding when and where thunderstorms could end up forming today. There are those that show storms initiating in Southern Manitoba beginning in the late afternoon, while other models have storm development beginning much later, once the cold front has crossed into Northern Ontario. To cover this range in possibilities, our forecast has a Slight risk from the Red River Valley to the Ontario border.

The hrdps model showing thunderstorms to the south and east of lake Winnipeg at 6pm CT, courtesy of WeatherBell.

If storms end up developing in Manitoba later today, they will likely start off as isolated supercell thunderstorms along the front that should then quickly merge into a line of storms that continues tracking eastward. These could end up being quite strong storms, especially since the same cold front triggered strong severe thunderstorms in Central Saskatchewan yesterday which produced some very damaging winds, large hail, and even a few tornado warnings.

The risks in Manitoba today are much the same if the storms end up developing here: very strong wind gusts that could be well in excess of 100km/h, hail up to the size of tennis balls, and torrential downpours that could lead to localized flooding. There is also the possibility of an isolated tornado, especially closer to the Ontario border.

We will be keeping an eye on how the situation unfolds today and if storms end up forming within the province later today, we will provide updates and probably livestream.

Strong Severe Thunderstorms with Tornado Threat Possible in Central Alberta and Saskatchewan Throughout the Day & Overnight

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There is a widespread chance for thunderstorms across Alberta and Saskatchewan today, with particularly strong storms also possible in parts of both provinces. A low pressure system has been developing in the Foothills this morning and is expected to track eastward into Saskatchewan by the mid to late afternoon. The warm and cold fronts associated with this low will be the trigger behind today’s thunderstorm development.

We’ve already begun to see some weak storms moving through parts of Central Alberta and additional isolated thunderstorms should begin to develop in the early to mid afternoon through the Foothills around Calgary and southward. Together, these storms are expected cross Alberta and into Saskatchewan through the remainder of the afternoon and evening. The thunderstorms are then anticipated to continue crossing Central Saskatchewan through the evening and into the overnight hours, before they finally begin to taper off.

Despite the storms expected to be isolated throughout the day, the risk is widespread because it has been difficult to pin down exactly where the storms will impact. There is also the possibility of some capping, which could limit thunderstorm development from even occurring.

Today’s storms, if and when they develop, could easily strengthen to become strong supercell thunderstorms, which could have the potential to produce damaging winds in excess of 100km/h, hail as large as golf balls, and heavy downpours that may lead to localized flooding. The risk of these storms stretches from Calgary to Wynard, SK, however, we have highlighted an area where the strongest of today’s storms could possible hit.

This area covers parts of East Central Alberta and West Central Saskatchewan, from Wainwright, AB to Warman, SK and including Saskatoon, and is the bullseye for the greatest severe weather threat this afternoon and evening. Severe thunderstorms that impact this region could possibly produce destructive wind gusts well in excess of 100km/h, as well as hail that could be as large as tennis balls and even heavier rain with an increased chance of flooding. This area could also end up seeing a tornado or two touch down.

We will be keeping a close eye on the situation throughout the day and we will likely be livestreaming later, once the thunderstorms have developed and strengthened.

Widespread Severe Thunderstorm Threat Across the Prairies Friday into Saturday, Tornado Risk in All Three Provinces

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The same system that brought some severe thunderstorms to Central and Northern Alberta yesterday, albeit much weaker than originally anticipated, could once again trigger severe thunderstorms today. This time, however, we’re looking at two distinct areas across the Prairies where severe thunderstorms could impact.

The first area of concern is across the southern half of Manitoba and in Eastern Saskatchewan, along the provincial border.

Isolated thunderstorms could start to develop along Saskatchewan-Manitoba border, especially in the area from Hudson Bay to Cumberland House, around the lunch hour. These storms should then track eastward into Manitoba fairly quickly and they could become severe while still in Saskatchewan. If the storms remain sub-severe as the enter Manitoba, it’s very likely that they will still strengthen to become severe as they continue eastward throughout the afternoon and evening.

Additional thunderstorm development could continue southwestward, back into Southeast Saskatchewan, throughout the afternoon. These storms are also expected to track eastward across Manitoba through the evening and overnight, leading to the widespread severe risk.

It’s worth noting that thunderstorm development throughout this entire area is slightly questionable. The environment will be primed with heat, moisture and instability, but there’s the possibility that capping in the atmosphere will prevent them from even forming in the first place. If this cap breaks, however, we could be looking at some explosive thunderstorm development.

Any storms that do develop will likely have the potential to produce golf ball-sized hail or larger, damaging wind wind gusts in excess of 100km/h, and heavy downpours that could lead to some localized flooding. There is also the risk of a tornado forming from storms that could move through Southwestern Manitoba and into the Interlake and Red River Valley in the evening. It’s possible that the tornado risk could extend into Winnipeg, but there is some uncertainty with how far east it goes.

Simulated radar from the HRRR model shows the possible location of storms at 5pm CT, courtesy of Weather Bell.

Meanwhile, there will also be the risk for severe thunderstorms to form in Southern Alberta, along the cold front that continues to push southward through the province.

Scattered thunderstorms could start to develop as early as the mid afternoon throughout the Foothills, mostly to the south of Red Deer. While some of the storms that could develop may become severe, those that develop from Airdrie to Claresholm will be the ones worth watching today.

It’s not until a bit later in the afternoon and into the evening that this area could see the development of thunderstorms. These particular storms will likely strengthen quickly into strong, long-track supercell thunderstorms that will travel eastward across Southern Alberta through the evening. It’s entirely possible that these supercell thunderstorms could maintain their strength through the evening and overnight as they push deep into Saskatchewan, possibly reaching as far east as Moose Jaw, and maybe even into Regina, in the early morning hours.

The threat from the severe storms in Alberta and into Saskatchewan today is very similar to yesterday, with the potential for golf ball-sized hail, damaging wind gusts in excess of 100km/h, heavy downpours that could lead to localized flooding, and even the possibility of a tornado. However, considering that yesterday’s High Risk from Environment Canada and expectations from weather models didn’t quite materialize, we’ve opted to go with a Slight Risk for Southern Alberta and Saskatchewan today. However, the possibility is still there for strong storms to develop so be mindful of any Watches or Warnings that may be issued.

Strong Severe Thunderstorms with Tornado Threat Possible in Central Alberta, Widespread Severe Risk Throughout Northern Alberta and into Saskatchewan

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Now that a warm front has brought some heat back into Alberta, active weather returns. Severe thunderstorms are possible across Northern and Central Alberta this afternoon, and into Saskatchewan later this evening. Central Alberta, in particular, could see some especially strong storms today, complete with the risk of an isolated tornado.

There have already been some scatted showers in Northern Alberta this morning, mostly in the northwest. Further development of thunderstorms is likely across the region and into Northern Saskatchewan this afternoon. These storms are expected to continue through the evening and into the early overnight hours before tapering off. It’s possible that some of these scattered storms could become severe throughout the day, with the potential for strong wind gusts up to 100km/h, toonie-sized hail, and heavy downpours.

The main area of concern for today, however, is in Central Alberta. Thunderstorms are expected to initiate in this region in the early to mid afternoon, which will gradually track eastward through the remainder of the afternoon and into the evening and overnight.

These storms likely strengthen into strong supercell thunderstorms by the late afternoon, which brings a strong risk to an area from Olds to Drayton Valley and east towards Wainright. There is the threat of hail larger than golf balls, damaging wind gusts in excess of 100km/h, heavy rain, and even the risk of an isolated tornado. These storms could be a major issue for motorists, especially between Red Deer and Edmonton, as they are expected to cross the QE2 during the evening commute.

The severe weather threat should decrease during the late evening and overnight hours, with the storms weakening as they continue along an eastward trajectory towards Saskatchewan. There is still the chance, however, that an isolated storm could remain severe during this time frame, which could still have the potential to produce large hail and strong wind gusts. The tornado risk, however, will decrease greatly.

⛈️ Strong Severe Thunderstorm & Tornado Risk For Ontario on Thursday Evening

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The summertime heat we’ve been experiencing is about to fuel some potentially strong thunderstorms in Ontario on Thursday, July 24, 2025. The main risk is in the evening and overnight hours but some areas could see strong storms in the afternoon as well, especially in Northeastern Ontario.

Some of these storms, particularly from the Bruce Peninsula and east towards Muskoka, Algonquin and potentially through parts of eastern Ontario may see a strong damaging wind storm (MCS), which is showing up on several high-resolution models. The timing looks to be late afternoon into the evening and overnight as it moves east towards Quebec.

Across other parts of Ontario, there is a risk for a cluster or line of storms from as far south as Essex County, all the way up to northeastern Ontario in the late afternoon into the overnight hours. Some models suggest it could arrive in the late afternoon but quite a few are suggesting the storms won’t arrive for most of us until the evening or overnight, especially in the east.

Damaging wind gusts, potentially exceeding 100km/h+, large hail, torrential rainfall with isolated flooding and frequent lightning are the main risks. We’re also seeing the potential for a few isolated tornadoes with this system, especially in orange (3) zone on the forecast map.

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In the image above, Environment Canada has issued their forecast for Thursday, highlighting all of the southwestern, central, golden horseshoe and eastern Ontario regions in a 2/4 “Moderate weather threat”.

Below is a regional breakdown based on Environment Canada’s forecast details:

📍 Location A: Portions of Southern & Northeastern Ontario

Hazards: 🌬️ Wind, 🌨️ Hail, 🌧️ Rain, 🌪️ Tornado, ⛈️ Thunderstorms
Timing: Afternoon and evening

Impacts:

• 🪁 Loose objects may be tossed

• 🏚️ Damage to weak buildings

• 🌳 Broken tree branches and downed trees

• 🌿 Possible damage to plants and crops

• 🌊 Flash flooding and pooling on roads

• ⚡ Power outages likely

Rainfall: Up to 50 mm

Confidence: Moderate
Impact: Moderate

Details:
Storms may bring wind gusts up to 100 km/h, rainfall up to 50 mm, hail up to 2 cm, and the potential for isolated tornadoes. Activity begins in the northwest and tracks southeastward through the day.

📍 Location B: Portions of Southwestern & Eastern Ontario + Greater Golden Horseshoe

Hazards: 🌬️ Wind, 🌧️ Rain, ⛈️ Thunderstorms
Timing: Late afternoon and evening

Impacts:

• 🌳 Broken tree branches and downed trees

• 🌊 Flash flooding and pooling on roads

• ⚡ Possible power outages

Rainfall: Up to 50 mm

Confidence: Moderate
Impact: Moderate

Details:
Scattered thunderstorms may produce wind gusts up to 90 km/h and locally heavy rainfall.

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More details ASAP about this storm risk. Stay safe on Thursday, folks!

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And a big thanks to the sponsor of this forecast; Kempenfest in Barrie! For those who don’t know, our own Adam Skinner will be performing at Kempenfest this year with his new rock band ‘Face The Lion’! They’ll be opening for the one and only Colin James on Saturday, August 2nd!

Here’s some more details on Kempenfest:

”Kempenfest presented by TD, is Barrie Ontario’s signature festival event, celebrating 53 years Aug 1-4, 2025, located across two-kilometres of Barrie’s beautiful waterfront. The annual event is one of Ontario’s largest waterfront festivals, featuring 300 arts & crafts vendors, a midway, community village, antiques, face painters, buskers, great food, a poutine village, and two stages of live music! Evening concert headliners include Shawn Desman, Colin James, The Washboard Union, and The Practically Hip, with many more!”

We hope to see you there!

Severe Storms Possible in Alberta & Saskatchewan Saturday with Tornado and Funnel Cloud Risk

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The cluster of severe thunderstorms that crossed through Alberta yesterday evening and overnight has been weakening as they have continued to track through Southern and Central Saskatchewan this morning. On the backside of these storms, there should be sufficient clearing in order for more severe thunderstorms to develop throughout Central and Southern Alberta and into Southwestern Saskatchewan.

Thunderstorm development should begin in the early to mid-afternoon, with scattered storms in Southern Alberta and into Southwestern Saskatchewan. The majority of these storms in Alberta will possibly become severe, but they aren’t expected to be too strong as they track eastward throughout the afternoon. These storms could bring some strong gusts, small hail, and heavy rain to areas in their path today.

Storms that could form to the north of Medicine Hat, however, and into Saskatchewan are expected to be the stronger, with the possibility to produce damaging wind gusts up to 100km/h and hail as large as Timbits, along with heavy downpours.

The possibility of strong storms developing to the west of Swift Current early this afternoon is worth noting. These particular storms could strengthen into a severe line that extends southward to the US border through the afternoon.

There is also the risk of a tornado or two forming during the early hours of these storms’ lives, in the late afternoon and the early evening, in an area that includes Shaunavon, Swift Current, Assiniboia and just into Moose Jaw. This risk does diminish as the line pushes eastward, with the storms expected to bring a strong wind and hail threat into Regina and to the east throughout the evening hours.

Overall, the intensity of storms will be dependent on how much daytime heating can occur and how much moisture can be funnelled northward following this morning’s active weather.

The dashed line outlines the funnel cloud risk from environment Canada

Back in Alberta, more storms could kick off in the Foothills a bit later in the afternoon. These storms will likely be more organized than the scattered pop-up storms expected earlier in the afternoon. There is a chance of them becoming severe in the evening as they track eastward through Calgary and areas to the south, with the possibility of producing strong wind gusts, toonie-sized hail, and heavy rain which could result in more localized flooding.

There is also the possibility that funnel clouds could develop today southeast of Edmonton, from Camrose to Oyen. It’s important to remember that funnel clouds have the potential to touch down as weak landspout tornadoes so be alert if you’re in this area today.

Widespread Severe Thunderstorm Risk Throughout Central & Southern Alberta, Threat of a Tornado South of Calgary

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A widespread risk of severe thunderstorms is in place for today across Central and Southern Alberta, with the threat of a tornado in parts of Southern Alberta.

Thunderstorm activity will kick off in the early to mid-afternoon through a large stretch of the Foothills, particularly in Central Alberta. These will be slow-moving storms that are expected to develop from the Calgary area to Grande Prairie and could have the potential to bring golf ball-sized hail and strong wind gusts to the region. These storms are also expected to have plenty of precipitation associated with them, which could result in some localized flooding before the storms taper off in the late evening.

There is the chance for storms to also pop up around Calgary and to the south at the same time, but these storms should be slightly weaker and could be short-lived. This will then be followed by some weak storms that will cross into the area from British Columbia in the late afternoon and early evening.

Storms in this second wave are expected to rapidly intensify into supercell thunderstorms as they track east of the Rockies, with the potential to hit the area with damaging wind gusts in excess of 100km/h and hail larger than golf balls. There is also the risk of a tornado or two developing to the south and southeast of Calgary, in an area that includes High River, Claresholm, Lethbridge, and Taber.

The storms in Southern Alberta will track much further east than those expected in Central Alberta earlier in the day. They will likely continue moving eastward towards Saskatchewan overnight, but are expected to lose some intensity during that time period.

Severe Thunderstorms Possible in Southern Alberta & Southwestern Saskatchewan Thursday, Along with Risk of Funnel Clouds

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Despite some cooler temperatures still sticking around, severe thunderstorms are likely today in Southern Alberta and into Southwestern Saskatchewan.

Thunderstorms have already been making their way through parts of Southern Alberta this morning and for the most part, they’ve been fairly weak. As we progress into the afternoon, some of these storms could strengthen to severe levels as they continue tracking east-southeastward. Additional thunderstorm development is also expected to occur closer to the US border through the afternoon, which will also probably become severe. The thunderstorms will track into Southwestern Saskatchewan later in the afternoon and will continue until the late evening hours, at which time they will move south of the border.

The area with the greatest risk of severe weather today will be in deep Southeastern Alberta and Southwestern Saskatchewan, as shown in yellow on the forecast map. In this region, storms could produce strong wind gusts and Timbit-sized hail. These threats also also possible throughout the rest of Southern Alberta and Southwestern Saskatchewan, shown in green, but the risk is slightly lower.

The dashed line outlines the funnel cloud risk from environment Canada

There is also the chance for funnel clouds to form today to the north of where the severe thunderstorms are expected. This will be in the area from Calgary and Olds, eastward through Drumheller and Hanna, and just crossing into Saskatchewan to include the Leader area. If you’re in this region, it’s important to remember that funnel clouds can possibly touch down as weak landspout tornadoes.

Ottawa Area, Eastern Ontario in Bullseye for Thursday’s Widespread Severe Storm & Tornado Risk; Isolated AM Risk for Southwestern Ontario & GTHA

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The oppressive heat that has been locked across Southern Ontario the past week is on the way out. But first that relief will come in the form of a cold front that is likely to clash with the hot air to create some strong thunderstorms ahead of the front.

Some of these storms, particularly in Eastern Ontario during the afternoon on Thursday could reach severe levels with strong wind gusts being the main threat. One or two tornadoes are also possible with the strongest environment being along a corridor from Tweed to Ottawa.

With the cold front already on our doorstep as of early Thursday morning, it is expected to gradually slide across Southwestern Ontario and the Golden Horseshoe through the overnight and pre-dawn hours on Thursday.

While this isn’t ideal timing for storm development, we can’t rule out some nocturnal development. And if these developments occur, the environment could certainly support a few marginally severe storms primarily with strong wind gusts and heavy rainfall.

The tornado risk isn’t zero, but it’s also not particularly strong due to the timing of the overnight storms. But the environment could support a brief spin-up through Southwestern Ontario into the GTA, but it’s very questionable.

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For Deep Southwestern Ontario, we are looking at the bulk of the risk between midnight and 6am with non-severe storms potentially continuing until 9am. These storms could bring isolated damaging wind gusts, nickel-sized hail and 50-100mm of rain.

In Southwestern Ontario, the risk follows a similar overnight pattern as Deep Southwest, though it’s slightly more delayed. The environment will still support some isolated strong wind gusts and localized flooding, but again, the timing works against widespread severe development. The threat of large hail and a brief tornado is low, but not zero. The risk should ease by the time we hit the late morning hours.

For the Golden Horseshoe, storms are expected to roll through in the mid-to-late morning hours, primarily between 6:00 a.m. and 12:00 p.m. Similar to the regions farther west, the overnight timing limits storm strength, but a few marginally severe cells are possible.

Gusty winds, heavy downpours and nickel-sized hail are the main concerns. The tornado risk is quite low, though not completely off the table. Things should quiet down quickly as we head into the early afternoon

In Central Ontario, storms may get going a bit earlier compared to the GTA, potentially arriving in the pre-dawn hours and continuing through the morning.

The main threat here also leans toward damaging wind gusts and flooding, especially if storms repeatedly track over the same areas. Nickel-sized hail is possible, and while the tornado risk is low, it’s not zero. Timing should help reduce the severity, but there’s still a window for a few stronger cells.

Eastern Ontario is where the severe threat becomes much more notable. As the front progresses into a more unstable environment in the afternoon, the potential for strong storms ramps up.

Damaging wind gusts appear to be the most likely hazard, but one or two tornadoes are also possible, particularly along a corridor from Tweed to Ottawa, where models show the strongest instability and tornado environment overlapping.

Hail around quarter-size and localized flooding are also concerns with any stronger storms that develop.

Southeastern Ontario will also be in the bullseye for strong to severe storms, particularly from late afternoon into the early evening. Kingston through Brockville and into Cornwall sits right along the corridor of stronger wind potential.

Wind gusts may reach damaging levels, with a few storms capable of producing quarter-sized hail. Flooding is also possible in areas that get hit by repeated rounds.

While the tornado risk isn’t as pronounced as the Ottawa Valley, it’s still something we’ll be watching closely.

For our updated map, it’s largely unchanged from our preliminary forecast. The main changes we made was shrinking the ‘widespread’ risk zone to cover Eastern Ontario only. The latest data suggests that the Niagara region is less likely to see storms so the support for a widespread risk is no longer there.

We have also extended the isolated risk into the rest of Southwestern Ontario to cover the very questionable severe risk during the overnight and early morning hours.

For the tornado risk, while there is a non-zero risk for a tornado across all parts of the severe risk, we have focused it on the Ottawa Valley. This is where the latest model data continues to show the strongest tornado risk. Mainly during the mid to late afternoon hours.

There is also a more heightened tornado risk along the London to Hamilton corridor during the morning hours. While the risk isn’t super strong, this is where we believe a tornado is most likely to occur if one does occur in the morning.

The storm risk should taper off around the dinner hour as storms move out into Quebec and Upstate New York.

Heat Wave Ends With a Bang: Widespread Severe Thunderstorm Threat for Southern Ontario on Thursday

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As Southern Ontario continues to deal with a prolonged heat wave, there is some relief on the way. A cold front is expected to sweep through the region on Thursday, bringing temperatures back down to near-seasonal levels. But unfortunately, that relief won’t come quietly.

We’re closely watching Thursday for the potential of severe weather across much of Southern Ontario.

Thunderstorms are expected to fire up along the cold front as it moves through the province, with the potential for widespread severe storms especially across Eastern Ontario, Central Ontario and possibly parts of the Greater Toronto Area (GTA) during the morning and afternoon.

These storms may pack a punch, bringing strong wind gusts, large hail, heavy rain and possibly even an isolated tornado. The best chance for any rotating storms (and tornadoes) will be in Eastern Ontario later in the day when the environment becomes more favourable for storm organization.

With more high-resolution models coming into range, we’re getting a better handle on how things may play out. Based on this data, we’ve put together a preliminary forecast map showing where the greatest risk for severe weather currently appears to be.

That said, this event is still just under 48 hours away, and plenty could still change. The timing, placement and severity of storms may shift, so expect updates over the next couple of days. We’ll be keeping a close eye on the data and will continue to post updates as things evolve.

ESTIMATED TEMPERATURE in °C - MAP FROM WEATHERBELL

At this point, it looks like the cold front will reach the western parts of Southern Ontario sometime during the morning hours. The strongest environment for severe weather will be just ahead of the front. But because of the early timing, the threat for severe storms in Southwestern Ontario and along the Lake Huron shoreline looks more limited.

Still, the setup could be just strong enough to trigger a few marginally severe storms by late morning or early afternoon as activity moves into Central Ontario and the Golden Horseshoe.

SIMULATED RADAR - MAP FROM WEATHERBELL

As the cold front continues eastward into the afternoon, this is when we expect storm activity to really ramp up. With daytime heating providing an extra energy boost, we’re watching the Peterborough to Bancroft corridor around noon, with storms potentially reaching Kingston and the Ottawa Valley by early to mid-afternoon.

Storms are expected to move out of Ontario and cross into New York and Quebec around the dinner hour. However, this is subject to change depending on the timing of the cold front.

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Given the setup, we’ve gone with a ‘widespread’ (level 2 out of 5) severe risk for much of Eastern Ontario. This includes the potential for several severe thunderstorms capable of producing damaging wind gusts, hail and heavy rainfall.

We’ve also extended this risk into parts of the Niagara region where some models are hinting at rapid storm development during the early afternoon before storms cross the border.

The rest of Southern Ontario, excluding Deep Southwestern Ontario and the Lake Huron shoreline, falls under an ‘isolated’ (level 1 out of 5) severe risk. Most storms in these areas will likely stay below severe limits, but a few could briefly become marginally severe during the morning or early afternoon.

Currently, Deep Southwestern Ontario and Northeastern Ontario are not in the risk zone for severe weather on Thursday. That’s due to the early arrival of the cold front which will likely move through these areas before storms have a chance to fully develop. That could change should the cold front arrive later in the day when the environment is strongest.

ESTIMATED Morning LOW in °C - MAP FROM WEATHERBELL

In the wake of the cold front, temperatures will drop significantly Thursday night into Friday morning. Some higher elevation areas in Central Ontario could wake up to morning lows in the upper single digits!

Most of Southern Ontario will see lows in the low to mid teens, which will be a welcome change after several nights of muggy 20°C+ lows.

ESTIMATED DAYTIME HIGH in °C - MAP FROM WEATHERBELL

Daytime highs on Friday will also cool back to near-seasonal values, with most of the region seeing mid-20s. But enjoy it while it lasts. A gradual warm-up is expected over the weekend with temperatures climbing back into the upper 20s and even low 30s by early next week.

Strong Severe Storms Possible in Central Alberta & Saskatchewan, Uncertainty Further East and into Manitoba

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There are two areas across the Prairies where there is the risk of severe thunderstorms today. The difference between these two areas, however, is the likelihood of storm development, with storms in Central Alberta and Saskatchewan looking much more likely to occur than those in Eastern Saskatchewan and into Manitoba.

A cold front that will track through Alberta and Saskatchewan today is expected to begin triggering thunderstorm development early this afternoon in West Central Alberta. These storms should intensify into a line of strong severe thunderstorms as they approach the QE2 corridor, particularly around Red Deer.

This line of storms should maintain its strength for several hours, travelling eastward across Alberta through the afternoon. The storms will then cross into Saskatchewan by the late afternoon/early evening and continue their eastward trajectory, gradually weakening later into the evening and overnight.

Borderline destructive wind gusts of up to 120km/h are possible from Red Deer eastward towards Saskatoon as the line of severe thunderstorms move through the region. Furthermore, hail as large as golf balls and localized flooding are concerns, along with the possibility of one or two embedded tornadoes.

Additional scattered thunderstorms could pop up behind the main line in both Alberta and Saskatchewan throughout the day and continuing overnight, but these storms are expected to be weaker. For those attending the Stampede today, there is the chance for an isolated storm, but the greatest risk for severe weather will remain to the north.

Meanwhile, there is also the risk of severe thunderstorms in Eastern Saskatchewan, along the Manitoba border, and eastward into Manitoba as the cold front makes its way into this area. In particular, parts of Southern Manitoba could be the main target of these storms.

Modelled CAPE (Convective available potential energy) as of 5PM CT highlighting southwestern Manitoba as the area with the most energy

All the ingredients for severe thunderstorms are expected to be in place today in this area, with heat and energy funnelling northward throughout the day ahead of the arrival of the front. Despite this, a strong cap will also be in place, so whether or not storms actually form remains questionable. Short-term weather models are not even showing any thunderstorms developing in this area, further cementing the uncertainty here.

IF thunderstorms end up breaking through the cap, it’s not expected to occur until the evening, but the storms could become quite strong. Large hail will be the main concern with these potential storms, with golf ball-sized or larger appearing possible. Strong wind gusts and torrential rainfall, possibly leading to localized flooding, could also be associated with storms that develop. This situation will certainly bear monitoring throughout the day.

It’s also worth noting that temperatures across the Prairies, with the exception of most of Southern Manitoba, can expect to see more comfortable temperatures tomorrow following the passage of the cold front today.