Severe Thunderstorm Risk to Kick Off the Week in Southwestern Ontario on Monday

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It has been quite an active few days when it comes to severe weather across the U.S., with a multi-day tornado outbreak leading to devastating scenes in Nebraska, Iowa, and Oklahoma.

Now, the severe weather threat shifts northeast, including the potential for strong storms in Southwestern Ontario starting Monday afternoon and continuing into the evening hours.

Thankfully, the threat here doesn’t appear to be as severe as what was experienced over the weekend in the U.S. However, we could still see damaging wind gusts of 90 to 100 km/h, hail up to the size of quarters, and there's a low chance of an isolated tornado.

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Storms have already started popping up over Michigan as of the early afternoon, and the latest data suggests that the environment is favourable for continued strengthening as they track northeast.

These storms are expected to cross over Lake Huron sometime between 2 to 5 PM and make landfall between Grand Bend and Kincardine. Strong wind gusts and an isolated tornado risk are the main threats with this cluster of storms.

Further south, there may be a second cluster of storms moving into the Windsor area sometime in the early to mid-evening hours. Some models suggest this won’t occur until after sunset, which would lead to a lower severe threat as the effects of daylight heating diminish.

If the storms arrive earlier than expected, the environment would be capable of supporting storms with damaging wind gusts and small hail as the main threats. Again, the tornado risk is low, but we can’t completely rule out a brief spin-up.

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Non-severe thunderstorms will continue throughout the overnight hours into Tuesday morning. This risk extends from Southwestern Ontario through the Golden Horseshoe and into Eastern Ontario along the Lake Ontario shoreline.

Severe Thunderstorms Target Parts of Southwestern Ontario on Wednesday With Tornado Threat

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The saying "April showers bring May flowers" certainly holds true this year in Southern Ontario, where continuous heavy rainfall over the past few weeks has led to flood watches in various parts of Central and Eastern Ontario due to rising water levels.

Even more rain is expected in the coming days. Rainfall totals over the next few days are predicted to range between 10-20mm, potentially reaching 20-40mm in areas affected by thunderstorms.

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This impending rainfall also carries a risk of severe thunderstorms, particularly on Wednesday in Southwestern Ontario, driven by a surge of warm air that could push temperatures into the 20s in some locales.

This increase in temperature will play a crucial role in the development of severe weather conditions starting Wednesday afternoon. However, this will be primarily localized to Deep Southwestern Ontario, including Windsor, Chatham, and Sarnia, limiting the severe threat to these areas. In contrast, temperatures in Central and Eastern Ontario are expected to struggle to reach double digits.

A line of storms has already started forming in Western Michigan, extending from Grand Rapids to Kalamazoo. This line is anticipated to continue its eastward movement, reaching the Canadian border between 3 to 5 PM.

According to the latest data, conditions seem favourable for these storms to potentially become severe, featuring wind gusts over 100 km/h and large hail, possibly the size of ping-pong balls. The chance of a brief tornado cannot be entirely dismissed.

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Environment Canada has issued a severe thunderstorm watch that notably includes potential tornado risks for the following areas:

  • Chatham-Kent

  • Eastern Lambton County

  • Essex County

  • Komoka

  • Leamington

  • Petrolia

  • Pinery Park

  • Rodney

  • Rondeau Park

  • Sarnia

  • Shedden

  • Strathroy

  • Watford

  • Western Elgin County

  • Western Lambton County

  • Western Middlesex County

  • Windsor

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As the storm line advances towards London and subsequently the Niagara region by early evening, the severe weather threat is expected to wane due to diminishing environmental support. Nevertheless, isolated wind gusts still could reach 90+ km/h, and small to quarter-sized hail remains a possibility.

While Southwestern Ontario and the Greater Toronto Area might experience a few storms later tonight into early Thursday morning, these are likely to be non-severe.

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Late Friday Wind Storm to Give Way to a Snowy Start to the Weekend in Parts of Ontario With Up to 10cm of Snow

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The weather across Southern Ontario has been largely characterized by spring-like conditions, with temperatures soaring into the 20s and the season’s first widespread severe weather event occurring on Tuesday. This pattern continued into Thursday and Friday with heavy rainfall, but a change is on the horizon for the weekend.

Persistent rain across Southern and Northern Ontario on Friday is expected to transition to snow overnight into Saturday morning. For most areas, the snow should melt upon contact, with limited accumulation. However, higher elevations around Georgian Bay and into Northeastern Ontario could see snow accumulations of 5-10cm by Saturday afternoon.

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Before the snow arrives, strong wind gusts are anticipated to develop by Friday afternoon, continuing overnight into Saturday morning.

The strongest gusts, possibly exceeding 90 km/h, are expected along the Lake Huron shoreline and the southeastern shoreline of Georgian Bay.

The hardest hit regions include Kincardine, Goderich, Grand Bend, and Collingwood which could experience wind strong enough to potentially cause damage, including power outages.

In Southwestern Ontario and the Golden Horseshoe, wind gusts are predicted to range from 70 to 90 km/h. Eastern Ontario will see less impact, with wind gusts expected to stay below 70 km/h. The wind is expected to subside by sunrise on Saturday.

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Northeastern Ontario will also experience strong gusts from Friday afternoon into the evening, with the areas directly north of Georgian Bay like Elliot Lake, Manitoulin Island, and Sudbury seeing the strongest gusts, approaching 80-90 km/h.

Widespread gusts of 70-80 km/h are expected in the rest of Northeastern Ontario, with lower gusts further north and west.

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As colder air sweeps into the region overnight, temperatures across Central Ontario and the Dundalk Highlands are likely to hover around the freezing mark into Saturday morning. This will cause the existing rain to transition into wet snow or flurries starting Friday evening.

With temperatures near freezing and recent rainfall, it’s questionable if the snow will stick or accumulate. The best chance for accumulation is in higher elevations such as Shelburne, Orangeville, and the Blue Mountains, where up to 5-10cm of snow could accumulate by Saturday morning.

Surrounding areas extending into Central Ontario, including Barrie, Orillia, Muskoka, and the Kawartha Lakes, might see minor accumulations of 2 to 5cm. This will vary based on local conditions, which could impact the snow's ability to accumulate. Regardless, the area is likely to experience sloppy conditions and icy roads as near-freezing temperatures cause existing rain on roads to freeze and create black ice.

The rest of Southern Ontario will see less than 2cm of snow or no snow at all, as will be the case in Deep Southwestern Ontario, the Golden Horseshoe, and Eastern Ontario.

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Colder temperatures in parts of Northeastern Ontario will allow for better snow accumulation, with areas like Timmins and Cochrane expecting up to 10cm of snow. The rest of Northeastern Ontario, except for regions north of the Georgian Bay shoreline, could see between 5-10cm of snow by Saturday afternoon. Less than 5cm is expected near the Georgian Bay shoreline due to warmer temperatures.

Snowfall is expected to cease across all parts of Ontario by early Saturday afternoon. The weekend will remain chilly for most areas, with temperatures stuck in the single digits on Saturday and Sunday, except in Deep Southwestern Ontario.

Windsor and Chatham may experience a pocket of warmer air, especially on Sunday, with temperatures potentially reaching the 20s and a risk of thunderstorms. The rest of Southern Ontario will see daytime highs in the mid to upper single digits on Sunday.

Severe Thunderstorm & Isolated Tornado Threat on Tuesday for Southern Ontario

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After experiencing a chilly start to April, Southern Ontario is finally feeling the warmth, bringing a more spring-like atmosphere to the region. This warmth will be especially noticeable on Tuesday as temperatures are expected to climb into the upper teens or even low 20s in some areas.

This warming, combined with an approaching cold front later on Tuesday, will set the stage for the development of thunderstorms.

A potent environment conducive to thunderstorm development is expected to materialize across Southwestern and Central Ontario during the afternoon, fueled by ample daylight heating from the warmer temperatures.

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As the cold front sweeps through the province starting in the late afternoon, a line of storms is anticipated to form, extending from North Bay towards Georgian Bay and into regions east of Lake Huron. According to the latest model data, these storms have the potential to become severe, with all types of severe thunderstorm threats being possible.

A slight severe thunderstorm risk extends from Kitchener through Orangeville and Simcoe County into Central Ontario, with a particular emphasis on the corridor from Orangeville to Bracebridge, where models indicate the most conducive environment for severe storm development. The primary window for these storms is between 3 to 8 PM, varying with the arrival time of the cold front.

These storms could bring large hail, up to the size of quarters or ping pong balls, wind gusts of up to 100 km/h, and the possibility of an isolated tornado cannot be ruled out.

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Areas within the isolated severe risk zone might experience a few storms, but the confidence is lower compared to those within the slight severe zone. As the evening progresses, the risk will evolve into a wind threat as the storms merge into a main squall line, advancing towards the Golden Horseshoe and Eastern Ontario.

In Eastern Ontario, non-severe thunderstorms are anticipated around midnight as the weakening line of storms moves through. Although the severe weather risk is expected to be low by the time the storms arrive, small hail and strong wind gusts are still possibilities.

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For Northeastern Ontario, an isolated severe storm threat is forecasted near the North Bay area as storms develop off Georgian Bay. The severity of the storms is expected to lessen further north, with non-severe thunderstorms predicted for the majority of Northeastern Ontario.

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Winter Storm Threat Looms for Ontario With Up to 30cm of Snow and 60mm of Rain by Thursday

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The beginning of April in Ontario is setting the stage for a dramatic shift in weather, as a moisture-laden system promises a variety of conditions across the region. This shift includes the potential for flooding rains, with predictions of 40 to 60mm of rain in parts of the Golden Horseshoe.

In addition, areas of Central, Eastern, and Northern Ontario are on track for significant snowfall, with totals ranging from 20 to 35cm in the most affected areas!

As outlined in our previous forecasts, this bout of active weather kicked off with strong wind gusts on Tuesday afternoon, expected to persist into the night.

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With the wind gradually subsiding, our attention now shifts to the substantial moisture being pumped into our region from the Gulf of Mexico. Initially, this precipitation will begin as heavy rain, with intense downpours expected overnight and into Wednesday morning across the Greater Toronto Area, extending into Central and Eastern Ontario.

However, by late Wednesday, colder air from the northwest will sweep in, prompting a gradual transition from rain to wet snow by the late afternoon in parts of Central and Eastern Ontario. Northeastern Ontario, already under colder air by the morning, may experience snow for the duration of this event.

The challenge in forecasting this system lies in the temperatures hovering near the freezing point, significantly impacting snow accumulation. Additionally, model predictions vary on the timing of the transition from rain to snow, some suggesting it won't occur until late Wednesday evening, while others indicate it will occur around 2 to 5 PM.

By Wednesday night, most regions, including the Golden Horseshoe, are expected to have transitioned to wet snow, with light to moderate snowfall persisting into Thursday morning and afternoon, concluding by Thursday evening.

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Elevation will be a crucial determinant of snowfall totals, with the highest accumulations forecasted southwest of Ottawa in Eastern Ontario's elevated areas. This includes Bancroft, Barry’s Bay, Algonquin Park, and Renfrew, with expected snowfall totals ranging from 20 to 35cm by Thursday's end.

For the Ottawa Valley, including Ottawa, Cornwall, Brockville, and Pembroke, snowfall totals are more uncertain, ranging from 10 to 25cm. This variability will depend on local dynamics and the ability of snow to stick to the ground. There is the potential that some areas will exceed our forecast if the snow can stick more efficiently to the ground.

Further south and westward, snowfall totals are expected to range from 5 to 15cm, including Kingston, Peterborough, Huntsville, and Sundridge. Local areas north of the Greater Toronto Area, particularly along the higher elevations of the Oak Ridges Moraine and Dundalk Highlands, may also see up to 10 to 15cm. This forecast is heavily dependent on temperatures, which may not drop below freezing until Thursday morning, affecting accumulation.

Areas east of Georgian Bay and away from Lake Ontario's shoreline are likely to exceed 5cm but should remain under 10cm. Regions directly along the Lake Ontario shoreline and parts of Southwestern Ontario will experience less than 5cm of snow, as rain will dominate these areas.

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In addition to significant snowfall in Central and Eastern Ontario, significant rainfall is anticipated along Lake Ontario's shoreline, including Prince Edward County, Oshawa, Toronto, Mississauga, Burlington, Hamilton, and Grimsby, with potential totals ranging from 40 to 60mm. This rapid accumulation, especially in urban areas prone to flash flooding, poses a substantial flooding risk.

Rainfall totals for the rest of the Golden Horseshoe, extending to the Dundalk Highlands and the Bruce Peninsula, are projected to range from between 30 to 50mm. Further north and east, where more snow is expected to mix in, rainfall totals of 20 to 40mm are likely.

Southwestern Ontario is expected to see lower rainfall totals of 10 to 30mm, with Deep Southwestern Ontario receiving less than 15mm.

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In Northern Ontario, heavy snow is the main concern, with the highest totals just north of Sudbury, anticipating 20 to 35cm of snow from Wednesday morning through Thursday afternoon.

For Sudbury and North Bay, snowfall predictions range from 10 to 25cm. Lower amounts are expected towards Georgian Bay due to rain mixing in, while totals will decrease sharply further north and west due to limited moisture.

Damaging Wind Storm Possible for Parts of Ontario Late Tuesday With 90+ KM/H Gusts

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March may have gone out like a lamb, but the beginning of April is roaring like a lion across Southern Ontario. This is thanks to a strong low-pressure system expected to track across the region. The system will bring a mix of weather conditions from severe winds and rain to the possibility of substantial snowfall as we advance into Wednesday and Thursday.

The immediate concern, however, arises from strong wind gusts anticipated to strengthen by Tuesday afternoon or evening and persisting into Wednesday morning. High-resolution models suggest that some of these gusts could reach damaging levels, surpassing 90km/h in Southwestern, Central, and Northeastern Ontario.

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The initial wave of moisture linked to this system has begun in Deep Southwestern Ontario by Monday evening. Although most of this moisture is expected to remain south of the border, areas along the Lake Erie shoreline could see heavy rain through the early hours of Tuesday. Rainfall totals of 10-20mm are forecasted, with localized areas around Windsor potentially receiving up to 30mm by Tuesday afternoon.

Following this system's departure towards New England, a second system will make its way into the Lower Great Lakes, rapidly intensifying upon its approach. This swift strengthening is expected to generate powerful wind gusts stretching from Michigan into Southern Ontario by Tuesday evening.

Additionally, there's a notable severe thunderstorm risk south of Lake Erie including Ohio and Pennsylvania for Tuesday evening. It looks like the cool waters of Lake Erie will shield Southwestern Ontario from the brunt of the severe weather.

Nonetheless, we cannot entirely discount the chance of an isolated storm making its way into our area. Should this occur, it could bring the threat of large hail and strong wind gusts. While a tornado remains highly improbable, it is not entirely off the table if a storm does cross over.

We will keep a close eye on this development and may issue a thunderstorm forecast should our confidence grow.

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Wind gusts are expected to gradually intensify through Tuesday afternoon, peaking late in the evening or shortly after midnight. Model predictions vary on the peak strength of these gusts, with the Canadian model being somewhat conservative, suggesting gusts may not surpass 80 km/h. Conversely, other models agree on the likelihood of damaging wind gusts exceeding 90 km/h, possibly nearing 100 km/h in some locales.

The areas most susceptible to the strongest wind gusts are to the east of Lake Huron, where gusts could reach between 100 to 115 km/h, affecting Goderich, Kincardine, Hanover, Owen Sound, and Wiarton.

Southwestern Ontario, extending to the Greater Toronto Area (GTA) and the Georgian Bay shoreline, might see wind gusts nearing 90 km/h, though variances are expected, and this represents a potential worst-case scenario. Some locations may fall short of the 90 km/h threshold.

In other parts of Southern Ontario, wind gusts ranging from 70 to 85 km/h are anticipated, with Eastern Ontario likely experiencing a lesser impact.

Power outages are a possibility in regions most affected, so it's wise to prepare for potential extended disruptions, particularly as the wind will accompany heavy rain overnight.

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In Northeastern Ontario, the strongest winds, possibly exceeding 100 km/h, will occur directly east of Lake Superior, including areas like Wawa and Sault Ste. Marie.

Gusts near 90 km/h are forecasted along the northern Georgian Bay shoreline, including Elliot Lake and Sudbury. The rest of Northern Ontario will generally see gusts below 85 km/h, with impacts diminishing further north and west.

The wind threat should subside by Wednesday morning in Southern Ontario but may linger into the early afternoon in Northeastern Ontario.

Following this wind event, attention shifts to the low-pressure system, which will stall over Michigan and draw in moisture from the Gulf of Mexico. This will funnel a significant volume of moisture into Southern Ontario through Wednesday and Thursday.

As colder air envelops Southern Ontario by late Wednesday, a transition from heavy rain to snow is anticipated, particularly in Northeastern, Central, and Eastern Ontario, potentially starting as early as late Wednesday afternoon. Some areas could see over 30cm of snow before it eases off late Thursday.

With the specifics of this transition and the extent of snow accumulation still uncertain, we are waiting to release our detailed forecast for rain and snow until Tuesday. What remains clear is that we are in for a deluge of precipitation over the coming days, with projections of 50-75 mm for certain parts of Southern Ontario. Flooding is a concern, regardless of whether the precipitation falls as rain or snow.

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Potential Snowy Start to April With Up to 20cm in Parts of Southern Ontario Starting Tuesday

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April Fools' Day might be on Monday, but the first week of April is shaping up to be no laughing matter in terms of weather for Southern Ontario. Starting Monday, the lower Great Lakes region is expected to be impacted by a series of systems throughout the week.

The initial two systems are projected to track south of the border, impacting Ohio and Pennsylvania primarily. There's a risk of severe weather on Monday and Tuesday, with a possibility it could extend into Deep Southwestern Ontario. However, the cold waters of Lake Erie should keep most of the severe risk south of the border. We will be monitoring and will have a forecast if it becomes more certain to have an impact on our region.

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These systems are set to bring heavy rain across the Lake Erie shoreline, from Sarnia to the Niagara Region and southward, with some areas potentially receiving 10-20mm of rain from Sunday night into Tuesday morning.

By late Tuesday, a third system is expected to sweep across Southern Ontario, bringing heavy rain throughout Tuesday afternoon and evening for most regions. Temperatures are set to drop from the low to mid-single digits to around or slightly below the freezing mark, causing the rain to transition to snow overnight into Wednesday morning.

The extent of this changeover, however, remains uncertain. Areas near the Lake Ontario shoreline and Deep Southwestern Ontario are likely to remain warm enough to prevent significant snow accumulation. In contrast, Central and Eastern Ontario, along with the higher elevations of the Dundalk Highlands northwest of the GTA, may experience sustained snowfall.

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This snow is expected to persist into Wednesday, with moderate to heavy snowfall continuing into the evening. Strong wind gusts may also contribute to blowing snow and reduced visibility in some areas. Light snow may linger into Thursday for Central and Eastern Ontario, but it won’t lead to much accumulation.

This forecast is preliminary and subject to changes as the system's path and temperatures near the freezing point could significantly affect overall snowfall accumulation.

As of now, Central and Eastern Ontario, including the Ottawa Valley and Muskoka, are anticipated to see 10-20cm of snow. The higher elevations of Algonquin Park and the Ottawa Valley are expected to be closer to the 20cm mark, with Ottawa and Muskoka likely receiving 10-15cm.

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The Dundalk Highlands area could see heavier snowfall, with Orangeville and Shelburne potentially receiving the most, possibly up to 10-20cm. However, this forecast is less certain due to temperature variations that may prevent freezing and cause some melting.

The rest of Central Ontario and the northern part of the GTA could receive 5 to 10cm by Thursday, with the possibility of higher totals if temperatures drop further than currently expected.

Areas near Lake Ontario's shoreline, the Niagara region, and the Lake Erie shoreline are expected to see less snow, with less than 5cm of accumulation. However, significant rainfall poses a concern for these areas, with potential localized flooding due to upwards of 50mm of rain.

We will continue to monitor the latest data and provide a more detailed forecast shortly. Remember, this forecast is very preliminary and could change significantly by Tuesday.

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Lake Effect Snow Targets Parts of Southern Ontario With Over 20cm of Snow Possible by Thursday

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Environment Canada has issued widespread snow squall warnings around Lake Huron and Georgian Bay today. The warning was issued because of the current frontal squall sweeping through the region, coupled with additional lake-effect snow expected to develop later today, persisting into Thursday morning.

Our forecasts often highlight the variability of snowfall totals during snow squall events due to the narrow bands involved. It's not uncommon for one area of a town to experience significant snowfall while an area just 5-10 minutes away receives barely any snow.

Predicting the precise location of these snow bands is challenging as even a slight shift in wind direction can significantly impact the outcome. Typically, we can provide a general idea of which regions will be most affected.

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However, this occasion is different, and we will not be producing our standard polygon forecast map. The three main high-resolution models we rely on for lake effect snow forecasts, HRRR & NAM from the United States and Canada's HRDPS. These models are showing significantly different outcomes, making it impossible for us to offer a forecast with confidence. We believe it wouldn't be responsible to predict something we're not sure about.

Instead, we're sharing the raw model data from these three models, allowing you to see the range of potential scenarios for your location and prepare accordingly. It's important to remember that model data often overestimates actual snowfall, so the amounts shown are likely too high. However, this data is useful for understanding where each model predicts the heaviest snowfall will occur.

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The models mainly diverge regarding the Georgian Bay squall expected to develop this evening and continue into Thursday morning. This squall is predicted to come ashore between Wasaga Beach and Collingwood, extending inland towards Barrie and possibly reaching the northern York Region.

The HRRR model estimates the most snow from this squall, suggesting over 50cm in areas just southwest of Barrie, including Wasaga Beach, Angus, and Alliston.

Keep in mind, that this is just raw model data, and the estimated 50cm is probably an overestimation, especially since the HRRR model tends to overpredict lake effect snow events. Nevertheless, if the HRRR model is accurate, this region could see 20-40cm of snow by Thursday.

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On the other hand, the NAM and HRDPS models predict a much weaker squall off Georgian Bay, with snow totals more in the range of 5-10cm (locally 15cm), and the NAM showing barely a few centimetres. This illustrates the wide variety of potential outcomes, from a few centimetres to over 20cm of snow.

Regarding the Lake Huron shoreline, there is slightly more consensus on overall accumulation, with all three models predicting over 20cm of snow between Hanover and London. However, this prediction still represents a very narrow band, meaning not everyone will see significant snow, and some may see only a few flakes.

Southern Grey and Bruce counties, along with Huron and Perth counties, are expected to bear the brunt of the heaviest snowfall, with totals ranging from 10-20cm and localized pockets possibly receiving 25-30cm. This includes areas like Kincardine, Goderich, Hanover, Listowel, Wingham, and Stratford. The Kitchener and Guelph region may also experience bursts of heavy lake-effect snow, with accumulations ranging from 5 to 10cm.

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Further south, all models concur on another band of lake effect snow southeast of Lake Huron, stretching from Grand Bend to the London area. This band is not expected to be as prolonged or intense as those further north, so snowfall totals will be more in the range of 5 to 10cm by Thursday afternoon.

As the lake effect snow winds down by Thursday's end, our focus shifts to a system arriving late Friday into Saturday that could bring significant snowfall to parts of Southern Ontario. There's some disagreement on the exact path of the system, and temperatures will hover near the freezing mark, potentially leading to mixed precipitation in some areas, affecting overall snowfall totals.

At this stage, a widespread snowfall of 10-20cm, with local amounts up to 25cm, seems fairly likely in parts of Southwestern Ontario and possibly extending into the Golden Horseshoe. We will issue a preliminary forecast soon, so stay tuned for updates!

Winter Is Not Done Yet! Parts of Southern Ontario Could See Up to 10-20cm of Snow by Monday

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Southern Ontario's recent spell of balmy weather made it feel like an early spring, yet winter has swung back into our forecast. A return of colder air has arrived just in time for the weekend, bringing a fresh batch of lake effect snow—aided by the unusually open waters after our mild winter.

Lake effect snowfall is expected to predominantly impact the southern shores of Lake Huron starting late Saturday and persisting into Sunday. The most affected regions could amass snow totals nearing 15 to 20cm by the end of Sunday.

Simultaneously, the outer bands of a system tracking up the Northeastern United States might deliver accumulating snow, primarily to Ontario's far eastern regions beyond Ottawa. These areas could see accumulations of 10 to 15cm by Monday morning.

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As of Saturday evening, we've witnessed a temperature dip across Southern Ontario, with expectations for the mercury to descend below freezing overnight. This shift sets the stage for lake effect snow development along the Lake Huron and Georgian Bay shorelines, particularly overnight and into Sunday morning.

Heavy lake effect snow is forecasted for areas stretching from Goderich to southward through Grand Bend and even into London, and south of Georgian Bay, encompassing the Meaford and Collingwood area.

The peak of this lake effect snow event is predicted for the pre-dawn hours on Sunday, continuing into early afternoon and gradually lessening by evening.

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Snow Squall Accumulation Disclaimer

Forecasting the exact snowfall accumulation for a specific location in a lake-effect snow event is extremely challenging. This is because of the highly localized nature of snow bands, which can lead to significant variance in totals even over short distances.

Therefore, you may notice our forecast shows significantly more snow than your weather app (including our own app). App-based forecasts often struggle with lake effect snow events due to their localized nature and reliance on data focused on larger macro-level weather events. This results in a failure to accurately capture the squalls, which operate at a micro-level, leading to intense snowfall totals.

Our forecast may still be off if the wind direction varies slightly from what the models predict, causing the snow squall band to form further north or south. That's why our forecasts use broader zones to account for this variability, meaning not everyone within these zones will see the significant totals. Essentially, we're indicating that a location within this area could see the forecasted amount.

The latest data indicate the most substantial snowfall will be found in areas like Goderich, Grand Bend, Lucan, and London, where totals may surpass 10cm, with localized areas potentially receiving 15-20cm. Elevated regions southwest of Collingwood are also likely to see over 10cm of snow.

Neighbouring regions such as Port Elgin, Wingham, St. Thomas, Meaford, and Collingwood might see up to 10cm, depending on the strength of the lake-effect snow. Lesser amounts, under 5cm, are anticipated for the rest of Southwestern Ontario and the Golden Horseshoe.

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Beyond the lake effect, heavy snow is forecasted to develop overnight in far Eastern Ontario as outer bands of precipitation from the slow-moving Eastern Seaboard system linger in the region.

Persistent snowfall will continue across areas east of a line from Kingston to Ottawa throughout Sunday, possibly continuing overnight before fizzling out just after Monday's sunrise.

Regions including Hawkesbury, Alexandria, and Cornwall could see totals exceeding 10cm by Monday morning. The area from Ottawa south to Brockville might approach snowfall close to 5cm. As we move westward, expected accumulations will quickly decrease, with less than 5cm forecasted due to the sharply declining precipitation gradient.

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Messy System Targets Ontario This Weekend With Significant Rain to the South and Heavy Snow to the North

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The opening week of March has been notably calm in Southern Ontario, with minimal active weather events and a generous serving of above-seasonal warmth and predominantly clear skies. A few rain spells have visited us over the last several days, with temperatures occasionally leaping into the 20s, setting records on Tuesday and Wednesday in some locations.

Yet, as we move towards the weekend, we anticipate a shift, with a looming system poised to bring substantial rainfall across Southern Ontario. In contrast, those in Northeastern Ontario should ready themselves for a considerable snowfall, with some areas potentially seeing up to 30cm.

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Following the departure of this system by late Saturday, a period of sub-freezing temperatures will return to Southern Ontario on Sunday, extending into Monday. This shift sets the stage for the possibility of snow accumulation in parts of Central Ontario, particularly Eastern Ontario and near Lake Huron and Georgian Bay, at the onset of next week.

Southwestern Ontario has already begun to experience heavy rain on Friday evening, anticipated to last into Saturday. The heaviest downpours are expected overnight and into the morning hours. The rain will start around midnight for Eastern and Central Ontario and is likely to persist into early Saturday afternoon.

Accompanying the rain on Saturday will be a surge of mild air, with daytime highs expected to reach the upper single digits, and potentially the low teens throughout Southern Ontario. While the Northern parts of the province will see a more resilient cold air mass, resulting in snow rather than rain.

Northeastern Ontario will see the onset of snow around midnight, with the mixing line expected near Elliot Lake to slightly north of Sudbury. Areas north of the line, including Chapleau and Timmins, will experience significant snowfall overnight into Saturday morning, with intense snow at times throughout the day.

Both the rain in the south and snow in the north will diminish as the evening progresses, as the system departs our region. By Saturday evening, a switch from rain to snow is possible in the northern regions of Central and Eastern Ontario. However, with the ground still saturated from previous rains and temperatures hovering just above freezing, significant accumulation is not anticipated.

Overnight into Sunday, light to moderate snowfall may occur in regions traditionally affected by lake-effect snow around Lake Huron and Georgian Bay. Eastern Ontario might also receive some flurries from the lingering bands of system-related precipitation. Currently, we predict a few centimetres of snow at most, though certain areas along the Lake Huron shore and south of Georgian Bay could receive up to 5-10cm. A more detailed forecast for Sunday's snow will be released on Saturday.

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Regarding total rainfall, Central and Eastern Ontario are set to receive the highest totals, with 25 to 40mm expected by Saturday's end, which may cause localized flooding. Widespread totals of 15 to 30mm are projected across most of Southern Ontario. Areas near the Golden Horseshoe, along the southern Georgian Bay shoreline, and over Algonquin Park could see a dry pocket leading to slightly less rain, with 10 to 20mm anticipated.

As for Northeastern Ontario, snow will be the dominant story with snowfall totals of 20 to 30cm in a broad swath encompassing Timmins, Kirkland Lake, Cochrane, and Kapuskasing. A sharp drop-off in accumulation is forecasted closer to the rain-snow mix to the south and drier areas to the north.

The Chapleau area can expect 10 to 20cm of snow, while less than 10cm is predicted for North Bay, Sudbury, Elliot Lake, and Sault Ste. Marie, with rain as the primary form of precipitation for those regions.

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Foggy & Warm Days Ahead for Southern Ontario: Widespread Dense Fog Starting This Weekend and Double-Digit Temperatures on Monday

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March has ushered in a tranquil period for Southern Ontario following the whirlwind of weather experienced in the final stretch of February. With temperatures climbing above the seasonal norm for the weekend, an area of fog has begun to descend across the region, foreshadowing a week that will start with several mornings blanketed in dense mist. While light drizzle is expected to accompany the fog, significant rainfall is not anticipated.

We are also watching the potential for what could be some of the warmest air we’ve seen this year so far across Southern Ontario starting Monday.

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As of Saturday afternoon, fog has started to materialize in parts of Southern Ontario. Current models predict that this fog will thicken as the day progresses into the night, with much of Eastern, Central, and Southwestern Ontario, along with the Golden Horseshoe, expected to face near-zero visibility conditions overnight and into Sunday morning.

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Sunday will see the fog dissipate to some degree after sunrise, but it may persist in certain areas throughout the day. This break will be short-lived, as a more extensive blanket of fog is forecasted to envelop almost all of Southern Ontario by Sunday evening, remaining into Monday morning.

This persistent fog could lead to school bus delays or cancellations on Monday, so it would be wise to prepare for potential disruptions. The fog is slated to make a return on Monday night, continuing into Tuesday, which could once again impact school transportation for a second consecutive day.

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The weather story of this week continues with a resurgence of mild conditions, particularly pronounced on Monday through Wednesday. A swath of the area will experience highs in the double digits, with the Windsor region potentially flirting with the 20°C mark on Monday for the second time this year!

As Tuesday gives way to Wednesday, steady rainfall is expected to sweep across Southern Ontario, predominantly in the latter half of Tuesday, persisting into Wednesday. Rainfall totals are forecasted to be modest, in the range of 5-10mm by Wednesday's end. Moreover, the potential for a thunderstorm on Tuesday cannot be discounted, although the severity is not anticipated to come anywhere close to what we saw last week.

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From Record-Breaking Heat to Blizzard; Snow Squalls Could Dump Upwards of 15-30cm on Parts of Ontario by Thursday

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The last 48 hours have been a weather whirlwind across Southern Ontario, beginning with thunderstorms and the season's first 20°C temperature recorded in Windsor on Tuesday.

This brief 'heatwave' has abruptly ended, ushered out by a sharp cold front that sent temperatures tumbling on Wednesday. By overnight into Thursday morning, we're bracing for wind chills that could make it feel like it's in the -20s!

The return of Arctic air to Southern Ontario typically means one thing: Mother Nature is about to fire up the lake effect snow machine over the usual snowbelt regions. The upcoming day will be no exception as we anticipate intense snow squalls affecting the Lake Huron and Georgian Bay shorelines, potentially dumping 15 to 30cm of snow by Thursday's end. Accompanying the heavy snow will be strong wind gusts, leading to blowing snow and localized blizzard conditions over the next 24 hours.

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The cold front in question has already made its way across our region as of early Wednesday afternoon, with temperatures in Southwestern and Central Ontario swiftly falling below freezing. This trend is expected to persist, bringing even colder air by evening.

Lake effect snow is set to begin this afternoon, initially starting off as disorganized and light. Expect light to moderate snowfall along the Lake Huron and Georgian Bay shorelines through the afternoon and evening. In Northeastern Ontario, snow squall activity is underway, focusing on the southeastern shoreline of Lake Superior between Wawa and Sault Ste. Marie.

As we move into Wednesday evening, models predict a more intense, focused squall developing between Wiarton and Kincardine, extending over Georgian Bay to come in land around Simcoe County. The Sault Ste. Marie region will also face relentless snow squall activity through the evening and overnight.

This squall is particularly noteworthy due to its significant moisture content, benefiting from an optimal fetch across Lake Superior, Lake Huron, and Georgian Bay. Consequently, we expect high snowfall rates, with the potential for the band to reach far inland, possibly affecting parts of the Northern GTA.

Driving conditions in Grey, Bruce, and Simcoe Counties, among other regions, will become treacherous overnight into Thursday morning. With wind gusts of 60 - 80 km/h, near-zero visibility and rapid snow accumulation are anticipated, raising the possibility of highway closures overnight.

Further south, areas away from Lake Huron like Listowel and Hanover may experience more scattered, less intense lake effect snow compared to the squall to the north.

By sunrise on Thursday, the main snow squall is expected to begin dissipating, although it will likely persist through the morning and early afternoon. The shifting wind direction may cause the squall to drift, dispersing snowfall over a broader area.

Lake effect snow activity off Lake Superior and Lake Huron/Georgian Bay is anticipated to wind down by mid to late afternoon on Thursday, as a slight temperature rise creates conditions less conducive to lake effect snow development.

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Snow Squall Accumulation Disclaimer

Forecasting the exact snowfall accumulation for a specific location in a lake-effect snow event is extremely challenging. This is because of the highly localized nature of snow bands, which can lead to significant variance in totals even over short distances.

Therefore, you may notice our forecast shows significantly more snow than your weather app (including our own app). App-based forecasts often struggle with lake effect snow events due to their localized nature and reliance on data focused on larger macro-level weather events. This results in a failure to accurately capture the squalls, which operate at a micro-level, leading to intense snowfall totals.

Our forecast may still be off if the wind direction varies slightly from what the models predict, causing the snow squall band to form further north or south. That's why our forecasts use broader zones to account for this variability, meaning not everyone within these zones will see the significant totals. Essentially, we're indicating that a location within this area could see the forecasted amount.

The areas hardest hit in Southern Ontario are expected to be Wiarton, Owen Sound, Chatsworth, Meaford, Collingwood, and Barrie, with 15 to 30cm of snow accumulation possible by Thursday's end.

It's important to note that models significantly diverge on the strength of these squalls, with some indicating potential for up to 50cm of snow in localized areas. Thus, there's a possibility for some regions, especially if the squall remains stationary overnight and into Thursday morning, to experience higher than anticipated snowfall totals.

Surrounding areas such as Port Elgin, Hanover, Keswick, and Orillia are generally expected to see 10 to 20cm, although the snow accumulation gradient will be extremely tight, meaning some areas may see little to no snow.

Less than 10cm of snow is forecasted for the rest of Southern Ontario, with accumulations above 5cm confined to regions east of Lake Huron and around Lake Simcoe. Durham region could approach 10cm of snow, depending on the inland reach of the Georgian Bay snow squall. Eastern Ontario and the Golden Horseshoe are expected to see less than 2cm of snow.

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In Northeastern Ontario, snow from a system will continue affecting the northern regions, including Timmins, Kapuskasing, and Cochrane, with 20 to 30cm of snow possible.

Lake effect snow will be more localized, with Sault Ste. Marie anticipated to receive 15 to 30cm of snow before the squalls taper off late Thursday. The rest of Northeastern Ontario can expect widespread totals of 5-15cm, with some areas seeing up to 20cm.

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Flash Freeze Threatens Wednesday Afternoon/Evening Commute Across Southern Ontario

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After experiencing a series of thunderstorms and Ontario's first 20°C temperature of the season recorded in Windsor on Tuesday, we're on the brink of a significant shift as we head into Wednesday. It feels like we're at the peak of a roller coaster, about to dive back down into winter-like temperatures.

This transition will be marked by a sharp cold front, leading to a rapid decrease in temperatures. Expect to see temperatures plummet from the upper single digits or low teens to well below the freezing mark within just a few hours on Wednesday. With roads and surfaces still wet from previous rainfall, a 'flash freeze' is almost certain, where all moisture on surfaces will quickly freeze, turning to ice.

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The severity of the flash freeze will differ across regions, with Central and Eastern Ontario witnessing the most dramatic temperature drops — from near double digits to the freezing mark within an hour or two in the afternoon to early evening. In Southwestern Ontario and the Golden Horseshoe, the temperature will initially drop to just above freezing, with a more gradual descent toward the freezing mark. This difference in temperature change rate will significantly impact the flash freeze threat, with a slower onset for these areas.

Following the cold front, lake effect snow will begin to form around Lake Huron and Georgian Bay from Wednesday evening into Thursday. While specifics will be detailed in a separate forecast, it's likely that traditional snowbelt regions could see upwards of 20-30cm of snow by week's end. However, this snow won't linger, as milder air is forecasted to return by the weekend.

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Wednesday morning will greet you with temperatures well above seasonal, in the mid to upper single digits through Central and Eastern Ontario, and possibly even double digits in the southwest. This warmth is extraordinary for this time of the year, especially considering it will occur in the morning, typically cooler than peak daytime temperatures. Windsor, Chatham, and Sarnia could see temperatures ranging from 12 to 15°C, making them the expected hotspots.

The onset of change will start later in the morning as the cold front approaches. Much of Southern Ontario will still experience mild temperatures of 6 to 9°C, except along the Lake Huron shoreline, where temperatures will be closer to 3°C, and near-freezing on the Bruce Peninsula.

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Northeastern Ontario will display the stark contrast in temperature gradients. North Bay and Sudbury will enjoy continued warmth from the south, with temperatures of 2 to 6°C, while Elliot Lake and areas towards Temiskaming Shores will be among the first to experience the cold plunge raging from -3 to -12°C.

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By early afternoon on Wednesday, the cold air will start to dominate, pushing the warm air east and causing temperatures to drop below freezing across much of Southwestern and Central Ontario. The Grey-Bruce region will see temperatures between -3°C to -5°C by 1 PM. The freezing line will sweep across Central Ontario and the Golden Horseshoe early in the afternoon.

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Northeastern Ontario will see Sudbury's temperatures drop from 3-5°C in the morning to near -9°C by the afternoon. While North Bay will follow Sudbury’s lead by the mid to late afternoon hours.

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By 4 PM, the last areas to experience the drop will be in the Ottawa valley, with temperatures nearing 12°C in the Brockville and Cornwall area. The rest of Southern Ontario will have already experienced the temperature drop and will hover at or slightly below the freezing mark through the afternoon.

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As night falls, the entire region of Southern Ontario will see temperatures plummet, with Eastern Ontario experiencing the drop around dinner time. Expect temperatures to range from -3 to -5°C in Southwestern Ontario and the Golden Horseshoe, while Central Ontario might see temperatures dip into the negative double digits.

By Thursday morning, the cold will intensify, with wind chills potentially making it feel like the -20s in parts of Southern Ontario. Be sure to bundle up before heading out the door on Thursday!

Rare February Severe Thunderstorm Risk for Parts of Southern Ontario on Tuesday

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As we bid farewell to February, Southern Ontario is set for a wild weather ride, with a rapid-fire succession of seasons in the span of just a few days. This climatic roller coaster is set to take off on Tuesday, bringing an influx of temperatures that are notably higher than what we're used to this time of year. Alongside the warmth, we brace for another hallmark of spring: the threat of thunderstorms.

Looking ahead, we have two distinct thunderstorm risks within a 48-hour window. The early birds in Southern Ontario might be in for a surprise with the first bout of storms expected during Tuesday's morning hours. Coming later in the day, there's the potential for more storm activity that could approach severe levels in the late afternoon and evening.

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As dawn breaks on Tuesday, we expect to see scattered showers and thunderstorms bubble up during the mid to late morning in Southwestern Ontario. Given the environment and minimal energy, these initial storms aren't likely to reach severe thresholds, but they may still pack a punch with lightning, potential for small hail, and strong wind gusts.

These storms will continue to track to the northeast toward Central Ontario and around Georgian Bay, lasting through the morning and into the early afternoon. Throughout the day, a surge of warm air from the southwest will see temperatures soaring into double digits across Southern Ontario.

While everyone across Southern Ontario will feel the heat on Tuesday, the highest temperatures will be found in Deep Southwestern Ontario, affecting locations like Windsor, Chatham, and Sarnia. The extent of this warm spell varies across the different weather models, but don't be shocked if Windsor sees its first 20°C day of the year on Tuesday!

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Progressing into the late afternoon, the escalating heat is likely to stir up atmospheric instability, setting the stage for thunderstorms starting late Tuesday afternoon. These storms are forecasted to pop up to our west, over Michigan and neighbouring states, where a robust environment for severe storms could take shape. However, this forecast remains up in the air, with some of the latest models suggesting storm development could be pushed back to the evening or even overnight which would lead to a lower severe threat.

If storms do materialize, we can't dismiss the possibility of an isolated severe storm tracking into Deep Southwestern Ontario. The primary hazards would be large hailstones, possibly as big as quarters, wind gusts reaching 90 km/h, and heavy downpours. While the tornado risk is not entirely absent, it's expected to remain primarily a concern on the American side of the border.

Another consideration is the lake temperatures this early in the season. While this winter hasn’t been cold by any measure, the lakes are still fairly cold compared to what we would see in the late spring or summer. Colder lakes have a tendency to drain storms of their energy as they cross over the lake and into our region. However, the stretch between Sarnia and Windsor is less shielded by the lakes, leaving it more vulnerable to severe storms crossing the border with little hindrance.

Storms are expected to persist across Southern Ontario into the overnight hours, leading into Wednesday morning. There is a questionable isolated severe risk for the Lake Erie shoreline and into the Niagara region just after midnight that is being picked up by some models.

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Apart from thunderstorms, Tuesday night is shaping up to be unusually mild, rolling into Wednesday morning with temperatures climbing overnight to remain in the double digits for much of Southern Ontario.

But don't be deceived by the unseasonably warm start to your Wednesday. A stark cold front is scheduled to slice through Southern Ontario from the northwest to the southeast beginning late Wednesday morning. This will result in a drastic drop in the temperature from the mid-teens to sub-zero levels in a matter of hours.

The potential for a flash freeze is particularly concerning, especially considering the preceding rain from the storms. Roads are expected to swiftly transition to treacherous sheets of black ice, complicating Wednesday afternoon's commute.

Stay tuned for more comprehensive details on the flash freeze threat, along with an update on the potential for snow as we move into late Wednesday and Thursday.

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Weather Whiplash in Ontario With Record-Breaking Heat, Severe Thunderstorm Risk & Flash Freeze This Week

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Get ready for a wild weather ride, Ontario! The old saying will hold true this week: "If you don't like the weather in Ontario, just wait five minutes—it'll change!" And change it will, with a full spectrum of seasons unfurling over the next 48 hours.

As we previously hinted, a ‘heatwave’ is set to roll in for Tuesday and Wednesday, with temperatures climbing into the teens. Parts of Deep Southwestern Ontario are even teasing the 20°C mark, according to some models!

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Thunderstorms are on the agenda for Tuesday, starting with morning storms and a potential severe risk by the afternoon and evening.

Fog, a recurring theme this season, is slated to make a comeback in certain areas on Tuesday and Wednesday. This will be accompanied by heavy rain, dumping 15-30mm by Wednesday morning. For parts of Northern Ontario, we could be looking at significant snowfall totals as the cold air hangs on there. This includes Kenora, Dryden, Kapuskasing, Cochrane and Timmins.

Take a look at Windsor's 10-day forecast—it's a real temperature roller coaster. We're climbing to the first high on Wednesday with temperatures soaring over 15°C, then taking a dive back to near seasonal norms by Thursday.

But hold on tight! We're heading back up for another warm spell this weekend, with the mercury potentially flirting with the 20°C mark by Monday.

For some perspective, the average high for Windsor at this time of year hovers around 3°C. However, the upcoming forecast anticipates highs that will consistently top the seasonal average. And this pattern of temperature swings? It's set to stick around into the early days of March.

Download our free app to view your local forecast.

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But don't pack away your winter gear just yet!

Remember, it's still February, despite what the balmy temperatures might suggest. Winter is gearing up for a comeback by Wednesday morning and afternoon. A sharp cold front will sweep through the province, one of the steepest we've seen in quite some time, with temperatures plummeting from the teens to below freezing in just a few hours.

Given the expected rain and mixed precipitation during this cooldown, we're likely to see road conditions turn treacherous with ice on Wednesday. A tricky commute is on the cards for Wednesday afternoon, and we can't dismiss the potential for school bus cancellations if the flash freeze risk materializes as the models predict.

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From late Wednesday into Thursday, snow squalls are expected to revisit the usual snowbelt regions, with wind chills plunging to near -20°C—a stark contrast to Tuesday's near-record warmth.

And the temperature roller coaster doesn't stop there. As we look towards the weekend and into early next week, another significant warm-up is on the horizon. Because these rapid temperature fluctuations are definitely healthy for our ecosystem! 🫠

We're putting together a detailed forecast, complete with several maps to navigate this complex weather pattern. It's a bit of a task, so bear with us as we compile all the necessary information. Stay tuned!

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Severe Thunderstorm Risk on Tuesday Close to Southwestern Ontario

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The Storm Prediction Center (SPC) in the United States has identified a 15% severe risk area in their Day 4 thunderstorm outlook for Tuesday, February 27, 2024.

This 15% severe risk zone is approaching Deep Southwestern Ontario, including Windsor. Currently, it stops just shy of Detroit, but the SPC's trend has been to extend it progressively northeast with each new forecast update.

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The SPC's forecast states, “As thunderstorms develop ahead of the front during the late afternoon and early evening, a severe threat is expected from the Ozarks northward into the southern Great Lakes. Wind-damage, and perhaps a few tornadoes would be possible with supercells and/or the stronger bowing line segments.”

Although it's unlikely for the severe threat to cross the border at this stage, the proximity to Windsor will make it something to watch. The potential for an isolated storm, primarily presenting strong wind gusts as a threat, cannot be entirely dismissed.

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Regardless of the severe threat, we're on the cusp of a welcome warm-up, accompanied by a few non-severe thunderstorms expected between Tuesday and Wednesday.

Stay tuned as we continue to monitor the situation and will provide updates as it evolves.

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