Update: Wintry Mix Continues, Pocket of Sub-Freezing Temperatures to Increase Snowfall Totals Tuesday

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It’s been a messy start to the week across parts of Alberta and into Southern Saskatchewan, with a low pressure system bringing mixed precipitation to the region today. This storm has been progressing as expected so far, but the latest data from weather models has resulted in some slight revisions to our forecast for Tuesday.

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Throughout the day Monday, we’ve seen temperatures above freezing across most of Southern and Central Alberta, resulting in precipitation falling as a rain-snow mix, and limiting overall snowfall accumulations. The exception to this has been in the Grande Cache area, where the temperatures have remained below 0°C and the precipitation has fallen as snow.

The single digit temperatures will continue overnight across most of Southern Alberta and Saskatchewan, but with being only being a degree or two above, or even at, freezing, we expect there to be a bit more snow accumulating beginning in the early morning hours Tuesday. This has been reflected by an increase in the forecasted snowfall for Taber, Brooks and north towards Strathmore and Drumheller.

As the temperatures begin to climb after sunrise, we will see the transition back to a rain-snow mix across the region. However, there is a small pocket where sub-zero temperatures will persist throughout the day, particularly in Medicine Hat, Maple Creek and the surrounding area. Steady snowfall will increase accumulations amounts to 5-10cm with locally higher amounts of up to 15cm possible in this area by the end of the day.

It is also expected that the precipitation from this system will push further eastward into Saskatchewan Tuesday afternoon and evening. By the late afternoon Tuesday, Arctic air will flood into the Prairies so the remaining light precipitation in Southern Saskatchewan at that point will fall as snow. As a result, we have extended the area covered by the 2-5cm range to include Outlook, Moose Jaw, and Assiniboia. Meanwhile, Saskatoon, Watrous, Fort Qu’Appelle, Estevan, and areas in between can now expect trace amounts (less than 2cm) of snow. The snow will diminish overnight, but scattered light flurries are possible in Southeast Saskatchewan Wednesday morning.

Temperatures to Soar Above 20°C Across Southern Ontario on Tuesday With Gusty Winds

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As we step into the first days of November, the temperatures outside might have you double-checking the calendar, as the unusually warm trend of this fall continues. This lingering seasonal tug-of-war between cold and warm air has led to temperature swings from near-freezing to over 20°C in the past few weeks.

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Despite the calendar saying November, it’ll feel more like early fall on Tuesday as temperatures rise to around 20°C across much of Southern Ontario. Accompanying this brief warm-up will be strong wind gusts, reaching 70-80 km/h in some areas.

A warm front moving across Southern Ontario is bringing in this surge of mild air, making its presence felt overnight into Tuesday. Already, spots around Lake Erie in southwestern Ontario are feeling this effect, with temperatures climbing near the 20°C mark by Monday evening.

In contrast, parts of Central Ontario and the Ottawa Valley have remained in the single digits, with areas near Ottawa hovering close to freezing. But don’t worry; that’s about to change as warmer air spreads in!

Overnight, temperatures will gradually rise, with most of Southern Ontario waking up to mild conditions in the mid to upper teens. In Central and Eastern Ontario, expect to start the day with temperatures in the lower teens.

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Throughout Tuesday, the warm-up will continue, with daytime highs near 20°C or slightly higher in some areas. The latest data suggests the warmest air will be centred along the Golden Horseshoe and deep southwestern Ontario, including cities like Windsor and Chatham, where temperatures could reach 21-24°C. Some locations may even approach record highs, though with records around 23-25°C in many spots, breaking them might be a tall order.

The rest of Southern Ontario, except for the Bruce Peninsula and northern parts of Central Ontario, will enjoy temperatures around 18-21°C. Northern regions, including Tobermory, Parry Sound, Huntsville, and Algonquin Park, will see slightly cooler temperatures around 15-18°C. Meanwhile, Northeastern Ontario will experience mild conditions, with highs in the low to mid-teens.

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TEMPERATURES 10-14°C ABOVE SEASONAL- MAP FROM WEATHERBELL

If 20°C temperatures in November seem strange, you're right! Daytime highs for this time of year are typically in the upper single digits or low teens, so we’re looking at temperatures around 10-14°C above average across Southern Ontario on Tuesday.

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Winds will also be a key feature on Tuesday, with gusts approaching 70 km/h across much of Southern Ontario by the morning. These winds should weaken somewhat later in the day but are expected to pick up again overnight into early Wednesday.

A few areas—particularly around Lake Erie, Niagara, higher elevations east of Lake Huron, and northeast of Georgian Bay—could see stronger gusts up to 80 km/h, although this will be highly localized. Most places should expect gusts around 70 km/h, with winds easing off by late Wednesday morning.

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Northeastern Ontario will see heavy rain beginning early Tuesday morning and lasting through the day and night, with rainfall totals reaching 30-50 mm by Wednesday afternoon in some spots.

Southwestern Ontario will also see moderate to heavy rain starting early Wednesday morning, which will then spread eastward to the Golden Horseshoe and Eastern Ontario by late morning. However, some models indicate that the rain might weaken before reaching Eastern Ontario, resulting in only a few millimeters. Southwestern and Central Ontario could see rainfall amounts of 5-15 mm.

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Wednesday will bring a dramatic change as a cold front sweeps across Southern Ontario, leading to a significant temperature drop by the day’s end. By Wednesday evening, temperatures across much of Southern Ontario will fall sharply into the low to mid-single digits, giving us a reminder that winter is just around the corner.

Messy Wintry Mix to Impact Alberta & Saskatchewan for the First Week of November

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The first week of November is going to have an active and messy start across Southern Alberta and Saskatchewan. The arrival of a low pressure system will bring widespread precipitation Monday and Tuesday, but the dominant type of precipitation that falls will vary throughout the region.

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The low pressure centre will cross into Alberta Monday morning in the Grande Cache area, bringing steady light snow to the area. As the low gradually travels southeastward across the province throughout the day and overnight, the precipitation will follow and spread across much of Central and Southern Alberta and continue for most of the day Tuesday. The low will move into Saskatchewan by early Tuesday morning, bringing precipitation to the southwest region of the province throughout the morning and into the late evening before dissipating.

The exact snowfall accumulation across Alberta and Saskatchewan from this system has been tough to forecast, with temperatures in the single digits for a large part of the region, meaning that the precipitation will fall as a mixture of rain and snow. This, combined with still mild ground temperature, should greatly reduce overall snow accumulations. As a result, we’ve gone with a more conservative snowfall forecast. The areas with the greatest snowfall potential, and the least mixing, will be found to the west of the low pressure system, behind its associated cold front and in the area with the coolest air, namely in the Grande Cache area and through the Rockies.

Spooky Skies Ahead! Southern Ontario Could See Warmest Halloween on Record; Up to 10-15cm of Snow Could Haunt Northern Ontario

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Excitement is brewing as Halloween night approaches, and the streets are set to fill with little ghosts, goblins, and creatures of the night. However, it seems Mother Nature may have skipped the “or” in Trick-or-Treat this year. While Southern Ontario is in for an unusually warm treat, there’s also a wintry “trick” in the forecast, as the first messy winter system of the season stirs up across the northern portion of the province.

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Before we dive into the chilly details, let’s savor the treat: a Halloween night warmer than most! Unlike Halloweens past, where bone-chilling temperatures hovered near or below freezing, this year brings weather that feels more like late summer or early fall. Temperatures across Southern Ontario will keep that warm spell lingering, with some areas possibly experiencing record-breaking highs for Halloween.

In years past, Canadian trick-or-treaters have bundled up with extra layers under their costumes to ward off the cold. This Halloween, they may find themselves shedding layers, with temperatures expected to reach the upper teens and even low 20s in some spots.

Prime trick-or-treating time around 8 PM will bring readings of 16-20°C across much of Southern Ontario, with slightly cooler temperatures between 14-16°C around Algonquin Park and the Bruce Peninsula. Daytime highs earlier in the day may reach the low or even mid-20s, with some areas potentially setting new temperature records.

However, Halloween night won’t stay warm for long. A cold front will sweep through late in the evening, quickly dropping temperatures as it ushers in much colder air overnight. Those celebrating late into the witching hour should brace themselves for temperatures plunging into the single digits by early Friday morning.

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Northern Ontario’s Ghostly Chill

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While Southern Ontario basks in warmer weather, the tale turns a bit chillier in Northern Ontario. Southern portions of Northeastern Ontario, including Elliot Lake, Sudbury, and North Bay, will enjoy temperatures between 12-16°C during Halloween evening. But for Central Northeastern communities like Chapleau, Temiskaming Shores, and Kirkland Lake, temperatures will drop to single digits, adding an extra shiver to the festivities.

Northwestern and Far Northern Ontario will already be feeling the effects of the cold front by trick-or-treat time, with temperatures hovering near or just below the freezing mark. In these areas, those venturing out for Halloween night will definitely need to incorporate extra layers into their costumes.

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So, Where’s the Trick?

PRECIPITATION TYPE FOR Halloween EVENING - MAP FROM WEATHERBELL

You may be wondering, with all this warm weather, where’s the trick in this Halloween forecast? The trick this year will be what’s coming down from the sky. Scattered rain showers are set to creep into Southern Ontario starting Thursday afternoon, with the heaviest rainfall likely in parts of Northeastern Ontario and along the western areas of Southern Ontario.

In fact, there could even be isolated thunderstorms around Georgian Bay. So if you’re out collecting candy, keep an eye on the skies, and take cover if you see lightning or hear thunder. Trick-or-treaters in Eastern Ontario, on the other hand, might just escape the rain until later in the evening.

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Fortunately, rainfall amounts across Southern Ontario are expected to stay light, with 5-15 mm in areas seeing the heaviest showers. Thunderstorm activity could increase these totals in very localized spots, but nothing overly dramatic.

The heaviest rain will be concentrated in Northeastern Ontario, stretching from Sault Ste. Marie through Sudbury and up to North Bay. Some of these areas are currently under a rainfall warning from Environment Canada, with up to 60 mm of rain possible from Wednesday night through Friday morning.

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A Halloween Surprise: Snow in Northern Ontario!

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And now, for the big Halloween scare! As rain moves across Ontario, colder air in the north will bring a chilling twist, transforming rain into snow by Thursday afternoon in some areas. The spooky snowfall is set to begin from Wawa up through Kapuskasing, with heavy snow expected to continue through the overnight hours into Friday morning.

For those areas in the “snow zone,” accumulation could be significant. A corridor stretching from Wawa to Kapuskasing may see up to 10-15 cm of snow by Friday morning, though actual amounts may vary based on temperatures near the freezing mark, which can affect how well snow sticks to the ground.

Surrounding areas, including Wawa, Kapuskasing, Timmins, and Cochrane, could see 5-10 cm of snow accumulation. However, warmer ground temperatures may mean that some snow melts on contact, reducing the totals.

Northeastern Ontario, north of a line from Sault Ste. Marie to Sudbury, may also pick up a dusting to a few centimetres of snow Thursday night into Friday, with up to 5 cm possible. Thunder Bay could even see a few flurries, though no accumulation is expected there.

So, Ontario, prepare for a Halloween that’s part treat, with warm weather for many, and part trick, with rain and snow making an appearance in others. However, you plan to celebrate, have a safe and spooky Halloween night!

Spooky Snow May Make an Appearance in Parts of Ontario to Kick Off Halloween Week

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The month of October has mostly brought calm and mild conditions to Ontario, with temperatures occasionally climbing above seasonal averages and minimal precipitation. But as we approach the final days leading up to Halloween, colder air is making a return, setting the stage for a possible wintry “trick” in parts of the region.

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This past week, temperatures in some areas reached the upper teens and even low 20s, but now a noticeable chill has settled in. Many spots across Southern and Northern Ontario are already experiencing single-digit highs as the warm air retreats.

As the weekend progresses, the cold will only deepen, with Sunday morning expected to bring temperatures near or just below freezing across the province. Afternoon highs will provide little relief, as most places in Central and Eastern Ontario will likely struggle to rise out of the single digits.

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A Weak Weather System and a Chance of Snow

PRECIPITATION TYPE FOR SUNDAY EVENING - MAP FROM WEATHERBELL

On Sunday, a weak weather system will begin to make its way into Northeastern Ontario and eventually move toward Central Ontario by the afternoon. This will likely bring some light rain showers to areas like Sault Ste. Marie, Sudbury, North Bay, and Muskoka. As colder air continues to push southward after sunset, temperatures will drop quickly, setting the stage for a possible transition from rain to wet snow in the evening.

While surface temperatures are expected to stay just above freezing until after midnight, colder air moving in aloft may allow the rain to change to snow as the night progresses. Precipitation will gradually spread southeastward, reaching Bancroft, Kingston, and possibly the Ottawa area.

There is some uncertainty about whether Ottawa itself will see any snowflakes, as models suggest that a dry air pocket may limit snowfall, keeping the bulk of moisture just to the south.

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Potential for Accumulation and a Hard Freeze

ESTIMATED MINIMUM TEMPERATURE ON MONDAY MORNING - MAP FROM WEATHERBELL

Temperatures will continue to drop overnight, leading to what is referred to as a “hard freeze” in areas like Sudbury, North Bay, Algonquin Park, and the Ottawa Valley. During a hard freeze, temperatures remain several degrees below freezing for extended periods, which could kill sensitive plants.

The drop in temperature may also allow for some light snow accumulation, with a dusting of 2-3 cm possible by Monday morning in some areas. Though not a significant amount, it could be enough to create slippery conditions on roads, making for a potentially slow and hazardous Monday morning commute.

Light flurries may linger across parts of Central and Eastern Ontario into late Monday morning, gradually tapering off around noon. With temperatures hovering close to the freezing mark throughout the day, any snow that does manage to accumulate will likely melt slowly. Motorists should remain cautious, as wet or slushy conditions could persist longer than usual.

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Midweek Warm-Up on the Horizon

ESTIMATED DAYTIME HIGH TEMPERATURE ON WEDNESDAY - MAP FROM WEATHERBELL

For those hoping for a break from the cold, a warm-up is expected by midweek. By Tuesday, daytime highs in parts of Southwestern Ontario could rebound into the low to mid-20s, with the warmer air spreading to Central and Eastern Ontario by Wednesday.

However, the return of milder weather may be accompanied by some wet conditions. A fast-moving weather system is forecast to pass through Southern Ontario on Tuesday, bringing the potential for 15-30 mm of rainfall across Central and Eastern Ontario between late Tuesday and Wednesday.

While the exact track remains uncertain, some models suggest the rain may shift further north, potentially impacting the area differently than initially expected.

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What’s in Store for Halloween?

ESTIMATED TEMPERATURE FOR HALLOWEEN AT 8 PM - MAP FROM WEATHERBELL

With Halloween fast approaching, many Ontarians are wondering what the weather will be like for Trick-or-Treating. As of now, forecasts indicate a chance of widespread rain across much of Southern Ontario during the afternoon, possibly lingering into the evening. Afternoon temperatures are expected to start in the mid to upper teens, but a cooling trend may bring them down to the low teens or even upper single digits by the time Trick-or-Treaters hit the streets.

There is still some disagreement among models regarding the exact timing of the rain. While it seems the heaviest precipitation may fall earlier in the day, there is a chance that skies could clear in time for the evening festivities, especially in Southwestern Ontario. Meanwhile, Eastern Ontario may be among the last regions to see any potential clearing.

Stay tuned as more details emerge in the days leading up to Halloween, and be prepared for whatever weather “tricks” or “treats” may come your way!

First Significant Snowfall of the Season Expected Across Alberta to Start the Week

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On the heels of some mild temperatures for the past week, a drastic cool down is already on its way courtesy of a strong cold front. Precipitation is expected along this cold front and unfortunately, the temperatures will dip low enough across much of Central and Southern Alberta for some of that precipitation to fall as snow, hitting the region in two rounds.

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The cold front has already started to make its way through Alberta from the north, bringing single digit temperatures to areas north of Red Deer and a large band of precipitation behind it spanning the width of the province. Most of this precipitation has been falling as rain, but to the west, through Grande Cache and Grande Prairie, there has been light snow. The rain will transition to snow moving eastwards this evening and overnight as the temperatures continue to fall and a low pressure centre moves in from the west, pushing the front and its associated precipitation towards Saskatchewan.

South of this first round of snowfall, conditions will stay dry until late Monday morning when additional precipitation will push its way into the region from British Columbia, crossing eastward across Alberta through the afternoon and evening. With the passage of the expected low pressure centre and a second cold front, temperatures will actually drop throughout the day so a large swath of Southern Alberta will see precipitation start off as rain, but transition to snow later in the afternoon as the temperature continues to drop. The exception to this will be in the Rockies, where the precipitation is expected to fall predominantly as snow, leading to upwards of 20cm of snowfall accumulation.

Forecasting the exact amount of snowfall for this event has been tough because the temperatures will not fall too far below 0°C, only a few degrees in most places. Furthermore, the ground is still warm across much of the province, meaning that overall accumulation should be limited to just a few centimetres beyond the mountains. Despite this, roadways could still become slick, so make sure to exercise caution when travelling over the next couple of days.

Early October Windstorm Will Blow Across the Prairies This Weekend

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The first weekend of October is shaping up to feel like true fall across the Prairies, with a strong low-pressure system bringing powerful wind gusts of 70-100 km/h. These winds are set to begin later this afternoon and continue throughout the day on Saturday. The prolonged high winds will likely strip many trees of their remaining leaves and could pose a serious hazard to traffic, especially for transport trucks and trailers

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The windstorm will kick off in the Alberta Foothills this afternoon, quickly spreading across Southern Alberta as the evening progresses. Expect pockets of gusts exceeding 90 km/h along the QE2 corridor south of Calgary and near the American border. These intense gusts won’t last long in Alberta, though, as the winds are expected to ease overnight.

The storm will move eastward into Saskatchewan through the evening and overnight hours. By morning, the low-pressure centre will stall and the winds will intensify, leading to widespread gusts approaching, and in some areas surpassing, 100 km/h across much of Southern Saskatchewan. These fierce winds will persist into the late afternoon and early evening.

The system will push into Manitoba by late Saturday morning, with strong winds continuing throughout the day before gradually subsiding. The strongest gusts, reaching over 90 km/h, are expected in the southwest corner of the province, but many parts of Southern Manitoba will still experience significant gusts.

Temperatures will cool down a bit following this windstorm, serving as just a taste of the fall storms we can expect as the season progresses.

Late Season Storms Bring a Slight Severe Risk for Southern Saskatchewan Tuesday Evening and Through Wednesday Morning

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As we continue later into September, it seems that summer is still hanging on, with some active weather this morning and into the afternoon and additional stronger severe storms beginning later this evening that will continue into Wednesday morning. The combined wind, hail, and tornado threat from the impending storms has resulted in a Slight Risk for a large portion of Southern Saskatchewan.

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The storms will start to develop as individual cells along the border in the early to mid-evening in Southwest Saskatchewan. This will be followed by a line of storms from south of the border that will make their way northward into the province later in the evening and into the overnight hours. A final round of storms is expected to arrive a few hours later, spreading much further north into Central Saskatchewan and weakening later into the morning. Due to the positioning of the low pressure that these storms will the centred around, areas closer to the Alberta border could see steady moderate rainfall lasting throughout Wednesday afternoon and evening.

These storms are expected to produce hail that could be larger than a toonie, along with damaging wind gusts upwards of 100km/h, and the possibility of one or two tornadoes. There is also the concern of localized flooding, particularly further west, where the storms and the subsequent extended period of rainfall could bring up to 100mm of rain.

Slight Risk for Severe Thunderstorms in Southern Manitoba This Afternoon and Into Tuesday Morning

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Following some morning and early afternoon rain, Southern Manitoba can expect more active weather with severe thunderstorms beginning this afternoon and continuing into Tuesday morning. The possibility of large hail and flooding caused by heavy downpours make this a Slight Risk in Southeast and South-Central Manitoba.

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The activity will begin this afternoon with a line of storms pushing northeastward into the region from North Dakota. Development of further storms will continue through the evening and into the pre-dawn hours of Tuesday, resulting in some locations seeing multiple rounds of thunderstorms. The storms that develop later into the evening could be more organized and are expected to be stronger that the afternoon storms.

These storms may bring some large hail, up to the size of a timbit, as well heavy rains that could result in areas of localized flooding. There will be some strong wind gusts that are expected to top out in the 90-100 km/h range and the possibility of an isolated tornado can not be completely ruled out.

Smoky Skies Ahead as Upper-Level Wildfire Smoke Sets In Across Ontario

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Over the weekend, Ontario experienced an early taste of late fall weather, with flurries making an appearance in parts of Northern Ontario. Meanwhile, out west, temperatures have been heating up, fuelling a resurgence of wildfire activity.

Now, this same weather pattern has shifted into Ontario, bringing rising temperatures along with increased wildfire smoke from out west including fires in Saskatchewan and Alberta. With a stagnant air mass in place, the smoke is expected to linger over the next few days.

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The good news is that most of this smoke will remain high in the atmosphere, resulting in limited impacts on air quality. However, some minor smoke may reach the surface, which could affect those sensitive to air pollution. The most noticeable effect of the smoke will be at sunrise and sunset, creating a striking orange-red hue in the sky.

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We began seeing smoke move into the region late Wednesday, and it’s expected to thicken overnight into Thursday. By sunrise, two pockets of heavy smoke are forecast over Southern and Northwestern Ontario.

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Throughout Thursday, the smoke will continue to blanket the skies, with the densest areas concentrated over Northern, Central and Eastern Ontario. Expect a stunning sunset on Thursday evening—perfect for photography!

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By Friday morning, the air mass will begin to shift westward, gradually clearing the smoke near the Manitoba border. However, Northeastern and Southern Ontario will likely remain under smoky conditions through Friday.

The heaviest smoke on Friday is expected along the Lake Superior and Georgian Bay shorelines.

Aside from the smoke, conditions will be ideal for this time of year, with above-average temperatures settling in across Ontario. This warm trend is expected to continue in the short term, with mild temperatures forecast into next week.

Stormy Start to Long Weekend in Southern Ontario With Potential Severe Risk on Friday

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As we kick off the Labour Day long weekend, traditionally seen as the unofficial end of summer in Southern Ontario, we're keeping an eye on the potential for some active weather on Friday.

Friday is likely to be the warmest day of the long weekend, with temperatures soaring into the mid to high 20s during the afternoon, and the humidex making it feel into the 30s. The only exception is Eastern Ontario, where daytime highs will peak in the low to mid 20s.

This warm air will fuel thunderstorms expected to develop later in the afternoon and continue into the evening hours. The main risk zone covers Southwestern Ontario along the Lake Huron shoreline, but parts of the Golden Horseshoe and Central Ontario could also see some severe storms.

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Based on the latest model data, instability will increase throughout the afternoon as daytime heating builds energy in the atmosphere. Earlier data suggested that storm development might be delayed until late evening or even overnight, which would significantly reduce the available environment to fuel these storms.

However, the newest model data shows storm development occurring much earlier, as soon as 4-5 PM—right during the prime time when conditions are most favorable. Most models agree on storms developing over Lake Huron in the late afternoon, then moving ashore between Owen Sound and Goderich. Initially, storms are likely to be isolated but could merge into a cluster as they track eastward through Grey and Bruce counties along the southern shoreline of Georgian Bay.

Additional storm development is possible to the southwest around Windsor, Sarnia, Grand Bend, and London, where the environment is actually stronger than in the north. Although there's lower confidence in storm development here, any storms that do form could become quite severe, with all hazards on the table, including a risk of an isolated tornado.

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Looking towards the evening, the earlier cluster of storms is expected to reach the Lake Simcoe region by early evening. By this time, the storms will likely have lost some intensity but could still pose a marginal wind damage risk through the northern GTA and parts of Central Ontario, including Simcoe County, Muskoka, and the Kawartha Lakes region.

Storms are likely to linger into the early overnight hours across Southwestern Ontario and the Golden Horseshoe. There are indications of a flooding risk, with storms ‘training’—where multiple storms move over the same area like a train—leading to significant rainfall amounts. It’s unclear exactly where these storms might set up, but if they occur over urban areas that are more prone to flash flooding, significant flooding could occur overnight on Friday.

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Currently, we’re going with a ‘slight’ (level 2/5) risk for severe storms in Southwestern Ontario on Friday. This is driven by the potential for fairly widespread damaging wind gusts. Hail up to the size of quarters and an isolated tornado risk are also possible hazards. We may need to introduce a more targeted ‘strong’ (level 3/5) risk zone in an updated forecast if confidence increases in where the storms will develop.

For those in Central Ontario and around the Golden Horseshoe, we’re assigning a ‘marginal’ (level 1/5) risk, mainly due to the potential for 90 km/h wind gusts later in the evening, along with flash flooding from multiple rounds of storms. While the tornado risk isn’t zero, it will be less of a concern by the time the storms reach these areas.

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Summer’s Last Hurrah as Heat Returns to Southern Ontario & Conditional Strong Severe Threat on Tuesday

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Ready or not, the end of summer is rapidly approaching, with just one week left before students head back to school. Signs of autumn are already peeking through, with Environment Canada issuing a frost advisory last week in Northern Ontario, and of course, the arrival of pumpkin spice latte season!

However, it seems that Mother Nature has decided to give us one last taste of mid-summer weather. The start of this final week has brought steamy conditions, with warmer air making it feel like the 30s or even low 40s in some areas thanks to the humidex.

Along with the return of hot temperatures, we can expect some active weather, with multiple rounds of thunderstorms likely on Tuesday, possibly extending into Wednesday. While there is some uncertainty regarding the exact strength and timing of these storms, there is a risk that some could reach severe levels, bringing damaging wind gusts, large hail, and the potential for one or two tornadoes.

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As mentioned, the dynamics of Tuesday’s storm risk remain highly conditional on timing. Some models suggest that decaying thunderstorm activity from Michigan could track into Southwestern and Central Ontario during the morning hours. If this occurs, it could deplete the atmospheric energy needed for storms later in the day when conditions are more favourable.

It's important to highlight that the potential for a "bust" in this event is moderately high, which is why we're focusing on the overall storm threat based on the environment, should storms develop.

The strongest conditions are expected along the southeastern shoreline of Lake Huron, extending into Deep Southwestern Ontario during the afternoon and evening hours. Storms could begin developing anytime between 12-1 PM and continue until sunset around 8 PM.

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There is higher confidence in storm development further northeast around Lake Simcoe and into Central Ontario, though the environment isn't as strong in these areas. Multiple rounds of thunderstorms throughout the afternoon and early evening could impact the North Bay, Muskoka, Parry Sound, and Algonquin Park regions, with flash flooding being the primary concern.

In addition to the daytime storm risk, there are indications of a nocturnal storm risk around midnight, continuing into the pre-dawn hours of Wednesday. A strong line of storms could form over Michigan or Lake Huron and track across Southern Ontario. However, this will depend on earlier storms and how much energy remains in the atmosphere.

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Regarding expected storm hazards, we're assigning a 'strong' risk (level 3 out of 5) for parts of Southwestern Ontario, including Windsor, Chatham, Sarnia, Grand Bend, and London, based on the potential for widespread wind damage—again, this is conditional on storm development. Large hail up to the size of toonies and one or two tornadoes are also possible threats.

There is a widespread 'slight' risk for the rest of Southwestern Ontario and into Central Ontario. All storm hazards are possible, including strong wind gusts, large hail, and an isolated tornado. As mentioned, storms in Central Ontario could bring a flash flooding threat, with rainfall totals potentially reaching 100 to 150mm in the hardest-hit locations.

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Further east, the Golden Horseshoe and a portion of Eastern Ontario are under a 'marginal' risk, where some storms later in the day or overnight could approach severe limits, primarily due to strong wind gusts and hail up to the size of quarters.

Threat of Massive Hail is the Driving Force Behind a Widespread Strong Severe Risk in Southeast Manitoba Sunday Afternoon IF Storms Develop

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It’s been a very active few days across the Prairies and this morning was no exception, with destructive wind gusts pummelling parts of East Central Saskatchewan and the Westman and Parkland Regions.

Unfortunately, this trend of dangerous severe weather will likely continue this afternoon, but this time the target will be Southeastern Manitoba. The possibility for massive hail across the region has resulted in this being a widespread Strong Risk for severe thunderstorms for this afternoon.

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Once again, weather models are struggling with pinpointing these storms, but the ingredients for severe weather should all be in place and there is a potential for severe storm development, which warrants a forecast. Today will be an “IF day” in the sense that IF storms end up developing, they are expected to be very strong and widespread across the region. With the intense heat and temperatures feeling into the low 40s, along with ample moisture and instability, the environment will be primed for storms, but a strong enough trigger will be necessary for them to occur.

This storm development could begin early this afternoon, as the existing line of storms pushes northeastward through the Interlake Region. Behind this, additional storms could develop along a cold front and make their way eastward through the Red River Valley and Interlake Region during the afternoon and the Eastman and North Eastman Regions in the evening and overnight hours. Whether or not this development actually occurs is still uncertain.

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If the severe thunderstorms end up developing this afternoon, the major threat will be very large hail. Golf ball-sized hail appears to be likely with these potential storms, with even up to tennis ball-size possible. Widespread damaging wind gusts over 100km/h would also be associated with these storms, as well as up to 100mm of rain resulting in localized flooding and the possibility of a tornado.

This could very well end up being a bust, but the threats involved in the event that storms do develop are quite significant and it’s important to be prepared.

Strong Risk for Severe Thunderstorms in Southeast Saskatchewan This Evening and Through Sunday Morning

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Southeastern Saskatchewan is in the crosshairs for severe weather once again, with some storms firing up along the American border later this evening followed by another round of strong storms early Sunday morning. The hail, wind, and tornado risk between the evening and morning storms makes this a Strong Risk along the southern border and a Slight Risk stretching through Southeast Saskatchewan and into East Central Saskatchewan.

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The activity will begin this evening with the development of supercell storms along the Montana border that will push northeastward through the late evening. These storms could be quite strong and will be followed by even more development from south of the border after midnight. This second round is expected to be more organized and bringing more widespread impacts as they follow the northeastward trend across Southeastern Saskatchewan through the morning.

These storms could be quite impactful with very large hail that will likely be golf ball-sized, possibly even larger, and widespread damaging wind gusts upwards of 120km/h, as well as one or two tornadoes. There is also the concern of localized flooding with heavy downpours that could bring up to 100mm of rain.

Greatest Severe Thunderstorm Threat for Saturday Afternoon Shifted West; Still Slight Risk for Southern Manitoba

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Following this morning’s thunderstorms, we are still expecting more severe weather for Southern Manitoba later today, however the anticipated strength of those storms has diminished and the area they’re expected to hit has also changed. The strongest storms of the day are now expected in Southern Saskatchewan, but the potential for damaging winds, large hail. and localized flooding still result in a Slight Risk for severe thunderstorms in the Westman, Parkland and Northern Interlake Regions.

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The exact timing of these storms is tricky to establish due to uncertainty between weather models, leaving three possible scenarios.

Scenario 1

Large storms could begin to develop in the mid-afternoon just east of the Saskatchewan border in the Parkland Region as isolated supercells which would travel northeastward across the province. Development of additional storms would continue through the evening and early overnight, following the same northeastward trajectory. These storms would then be followed by a more organized cluster of storms crossing through the region Sunday morning.

Scenario 2

Smaller storms could start to develop in the Parkland Region in the mid to late afternoon and quickly become more organized into a strong line that spreads into the Northern Interlake and travels southeastward through the evening before starting to fall apart approaching the Central Plains overnight. In this scenario, the storms Sunday morning would be weak, if they occur at all.

Scenario 3

A handful of small storms could pop-up starting in the later in the afternoon, once again in the Parkland Region, and continuing into the late evening, but not amount to anything too concerning. Then, in the early morning hours, a large cluster of storms could push northeastward into the region from Saskatchewan, followed by a second round of strong storms later in the morning.

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Regardless of which of the three scenarios unfolds, it is likely that there will be strong storms in Manitoba over the next 24 hours. The threats from these storms will be the large hail, with up to toonie-size likely and damaging wind gusts that could exceed 100km/h, as well as one or two tornadoes . There is also the concern of localized flooding because these storms are expected to occur over the same area. It’s important to note that the level of uncertainty between weather models means that this could very well end up being a classic “bust” day, but we believe that it is better to be prepared in the event that any one of these scenarios materializes.

Slight and Strong Risk for Severe Thunderstorms Across Southern Manitoba Saturday, Hitting in Multiple Rounds

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It will be a hot day across Southern Manitoba on Saturday, but there will be some active weather, in the form of a line of severe thunderstorms, to contend with before the temperatures start to climb. More storms will hit the region later in the day, but the timing remains a little unclear. Regardless, the risk of large hail and damaging wind gusts, along with the possibility of a tornado makes this a Strong Risk for severe thunderstorms in Southwestern Manitoba, including Brandon, and a Slight Risk across much of the rest of Southern Manitoba.

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The first line of storms will make their way into Southwestern Manitoba around sunrise Saturday morning, packing a punch with strong winds and large hail. These storms will lose steam as they travel eastward across the width of the province throughout the morning and into the early afternoon. Following this line of storms, it will be a hot day across the region, feeling closer to 40°C with the humidity, which should provide ample fuel for another wave of storms. The exact timing of this second line of storms is still uncertain. Some models are suggesting that the additional storms could start Saturday evening and make their way across Southern Manitoba overnight and into Sunday morning. On the other hand, there are other models that show the second line of storms developing in the early morning hours of Sunday and continuing into the early afternoon, followed by a third line of storms beginning Sunday evening. Due to this uncertainty, we will likely have a revised forecast for the secondary storm development posted Saturday afternoon.

The threats from these storms will be the large hail, with up to golf ball-size possible, as well as widespread damaging wind gusts that could exceed 100km/h and approach 120km/h, along with the possibility of a tornado or two touching down. There will also be a flooding risk, with these storms expected to bring up to 100mm, particularly to areas that will experience multiple rounds of storms.

UPDATE: Slight Risk for Severe Thunderstorms for Friday Now Extends into Calgary

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In an update to the forecast that was posted yesterday evening, we have extended the boundaries of the Slight Risk region to include Calgary and the entire Highway 2 corridor south of the city. The combination of damaging wind gusts, large hail, and the possibility of an isolated tornado from today’s has resulted in the Slight Risk for this area, along with Lethbridge, Medicine Hat, and Drumheller.

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Thunderstorms have already begun to develop in Montana, moving northward towards the border. They will start to cross into Alberta later this afternoon and early evening, spreading across Southern Alberta throughout the rest of the evening and overnight. It’s possible that the storms could become organized into a line that will push northeastward starting later in the evening which will impact a more widespread area than just isolated storms.

The main threat from these storms will be the hail, with up to toonie to timbit-size likely, as well as damaging wind gusts that could exceed 100km/h and even approach 130km/h. At this time, there does not appear to be too much of a flooding risk, with these storms expected to bring less than 50mm of rain over the span of a few hours. An isolated tornado can also not be completely ruled out.

Slight Risk for Severe Storms in Southern Alberta to Finish the Week; Forecast Could be Upgraded

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Friday will be another hot day across Southern Alberta and along with that heat comes severe thunderstorms. A combination of damaging wind gusts, large hail, and the possibility of an isolated tornado means that there will be a Slight Risk in an area that includes Lethbridge, Medicine Hat and north towards Drumheller.

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The storms will cross into Alberta from Montana in the south starting in the late afternoon and early evening, spreading across the region throughout the evening and overnight hours. It’s possible that the storms could become organized into a line that will push northeastward starting later in the evening that will impact a more widespread area than just isolated storms.

The main threat from these storms will be the hail, with up to toonie-size likely, as well as damaging wind gusts that could exceed 100km/h. At this time, there does not appear to be too much of a flooding risk, with these storms expected to bring less than 50mm of rain over the span of a few hours. An isolated tornado can also not be completely ruled out. The risk level could change with more data from short-range models so stay tuned for any updates to this forecast.

UPDATE: Isolated Strong Risk for Severe Storms in Southern Saskatchewan Beginning Wednesday Evening

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It will be another stormy day in Southern Saskatchewan on Wednesday, with active weather beginning later in the day and continuing through to Thursday morning. A combination of very large hail, damaging wind gusts and the possibility of tornadoes has led to us upgrading this forecast to a Strong risk, surrounded by a Slight Risk in the Southeastern region of the province.

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The storms are anticipated to start in the early evening Wednesday in the southwest as some isolated cells. These individual storms will quickly merge and become large clusters of storms that will move northeastward across Southern Saskatchewan throughout the rest of the evening and into the early morning hours of Thursday. The storms will become more organized as they move across the province, as well as becoming more intense, thus increasing the threat from Marginal, Slight and in an isolated area that includes Regina, a Strong risk.

The main threat from these storms will be the hail, with toonie to timbit size with isolated hail up to golf ball size, as well as damaging wind gusts that could exceed 100km/h. Heavy downpours will be associated with these storms and some areas, particularly in Southeast Saskatchewan, could see over 50mm of rainfall. There is also the risk of these storms producing one or two tornadoes so be sure to keep an eye out for watches and warning being issued by Environment Canada later in the day.

Heavy Rain and Moderate Winds Will Mark Ernesto's Passage South of Newfoundland Monday

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While tracking Hurricane Ernesto for the past few days, there was some uncertainty between models when it came to the path that the storm would take either through or around Newfoundland. Thankfully, it became clearer, as the storm continued its approach, that it would pass south of the Avalon Peninsula, greatly limiting the impacts to land.

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Ernesto restrengthened to a Category 1 Hurricane on Sunday and it will maintain that intensity as it makes its final push into Canadian waters later Monday morning. Precipitation from its outer bands will spread across most of Newfoundland as light to moderate rain starting in the mid-morning along the South Coast and moving northward across the province into the afternoon. Total rainfall amounts will be 5-20mm from this early rainfall.

By the time the storm travels to south of the Avalon Monday evening, it will have weakened to a tropical storm with wind gusts at its centre of 110km/h. The intensity of the winds will decrease further away from the centre and the strongest winds on land are expected in the Southeast Avalon, topping out at 70-90km/h. Across the rest of the Avalon and through the Burin Peninsula, wind gusts will be in the 50-70km/h range during the evening and into the overnight hours.

This is also the time frame in which Ernesto will bring the most precipitation to Southeast Newfoundland. The rain could be very heavy at times during this 6 hour window and up to 50mm could easily fall across most of the Avalon Peninsula and up to 30mm for the Burin Peninsula, with higher amounts locally. The rain and large waves from the storm could result in some coastal flooding, particularly along southwest-facing shorelines so be sure to exercise caution in these areas. By Tuesday, the storm will be well east of the island and the large waves will start to subside, marking another hurricane in the books for Newfoundland.

Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 18th at 9Pm