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.

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.

MODEL MAP FROM WEATHERBELL

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.

MODEL MAP FROM WEATHERBELL

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!

MODEL MAP FROM WEATHERBELL

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.

Snowy Surprise: Parts of Ontario & Quebec Could See Season’s First Snowflakes This Weekend

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As we enter the first full weekend of meteorological fall, Mother Nature is set to deliver a taste of autumn across Ontario and Quebec. A brief blast of cold air will cause temperatures to drop near the freezing mark during the pre-dawn hours on Saturday and Sunday.

Precipitation currently affecting Southern Ontario is expected to linger throughout the weekend. The heaviest rainfall totals are expected overnight Friday into early Saturday in Eastern Ontario, with localized amounts of 20-40 mm of rain possible.

The bigger story is when that precipitation wraps around into Western Quebec and Northeastern Ontario later on Saturday, continuing into the early morning hours of Sunday. With temperatures cooling into the low single digits and even colder air aloft, some of that precipitation may fall as wet snow.

It appears that locations like Timmins, Cochrane, Kirkland Lake, Temiskaming Shores, Deep River, and Algonquin Park in Ontario could see their first snowflakes of the season. In Quebec, areas such as Ville-Marie, Rouyn-Noranda, Amos, and Val-d'Or may also experience wet snow.

While it's unlikely that snow will accumulate, as it will be mixed with rain and ground surfaces are still too warm, there's a chance that colder-than-expected conditions could lead to a few slushy centimetres in some areas. Any accumulation will melt quickly after sunrise on Sunday as temperatures gradually rise.

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Speaking of Sunday morning, this is when the coldest air of this brief "cold snap" is expected across Ontario and Quebec. Morning lows will likely drop into the single digits across much of Northern and Southern Ontario and Quebec. In Northeastern Ontario and the Algonquin Park region, temperatures could dip to near freezing during the pre-dawn hours, increasing the risk of frost in addition to the potential for wet snow.

Further south, the coldest temperatures in Southern Ontario will be in the higher elevations of Central Ontario, east of Muskoka, where temperatures may plunge to around 2-5°C. It will be moderately warmer in Southwestern Ontario, the Golden Horseshoe, and Eastern Ontario, with morning lows ranging from 5-10°C. Those along the shorelines of Lake Ontario, Lake Erie, Lake Huron, and Georgian Bay will benefit from the warmer lake waters, keeping temperatures above 10°C.

In Quebec, expect low to mid-single-digit temperatures in the western portion of the province near the Ontario border on Sunday morning. Eastern Quebec, including Montréal and Québec City, will see lows in the upper single digits, ranging from 6-12°C.

WATERSPOUT RISK FOR GREAT LAKES ON SATURDAY MORNING (SORUCE: ICWR)

This cold air will also contribute to a potential waterspout outbreak over the Great Lakes this weekend. The highest risk is on Saturday, especially in the morning and afternoon, with a focus on Southern Lake Huron and Western Lake Erie. Waterspouts are also possible over Southern Georgian Bay, Western Lake Ontario, and even Lake Simcoe.

While waterspouts rarely threaten land, they can be hazardous for those on the water. In rare cases, waterspouts can come ashore, causing minor damage along the immediate shoreline.

The waterspout risk will persist into Sunday, with a focus on Eastern Lake Ontario.

Looking ahead to next week, warmer weather is expected to return to Ontario and Quebec. By late in the week, temperatures could climb back near the 30°C mark in Southern Ontario. So, while this brief taste of fall may be shocking, it looks like summer isn't quite finished yet.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

Rainy Start to the Week Across the Maritimes as Hurricane Ernesto Passes Offshore

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While tracking Hurricane Ernesto for the past few days, it was been clear that the storm would stay well offshore of Nova Scotia. This has been good news because it means that there would be very little impact from the storm across the Maritimes. The greatest threat will be moderate to heavy surf, along with riptides, that have already begun to arrive along the Atlantic Coast of Nova Scotia this evening which will continue through the day Monday and into early Tuesday. Despite the storm staying over open water, the Maritimes can expect a wet start to the week.

A band of thunderstorms will make its way northward from Ernesto and cross in Nova Scotia shortly after midnight tonight along the length of the province, but more concentrated to the eastern mainland and Cape Breton. This will be followed by a secondary band in the mid-morning, once again focused more along the eastern half of the province. These storms will bring localized downpours and could bring up to 30mm by the lunch hour. The threat of isolated onshore storms will continue throughout the afternoon and into overnight which could push into Southern New Brunswick and across PEI with some light rain.

Meanwhile, a secondary tropical air mass will bring rain to Northern New Brunswick beginning Monday afternoon, lasting until late in the day Tuesday. This rain will be quite heavy at times, especially in the Edmundston area, and could lead to up to 50mm falling. These two rounds of precipitation make for a very interesting looking rainfall map!

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

Hurricane Ernesto's Track Through Atlantic Canada Becoming Clearer; Could Maintain Category 1 Strength Deep into Canadian Waters

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Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 17th at 9Am

Hurricane Ernesto made landfall on Bermuda early this morning as a Category 1 Hurricane. The storm luckily weakened from a Category 2 in the few hours before landfall, but it still packed a punch with 135km/h winds. Now the storm will continue to churn northeastward into Atlantic Canada for the beginning of next week.

The Canadian Hurricane Centre is now issuing their own forecast track and there has been very little change in their prediction with their 9am update compared to the maps from the past two days. They maintain that the centre of Ernesto will stay well offshore of Nova Scotia and pass south of the Avalon Peninsula. Major weather models have made a shift since yesterday morning and now there is agreement that the centre of the storm will stay off the coast of Newfoundland. This is certainly good news because this will keep the strongest winds from hitting land, but it will still be an impactful storm.

Now that we’re starting to see a clearer picture of Hurricane Ernesto’s path through Atlantic Canada, we can more accurately forecast the impacts of the storm, especially for the Maritimes. Pounding surf will hit the Atlantic Coast of Nova Scotia beginning late Sunday and continuing through Monday. Rip currents will also be a concern in these coastal areas. Light rain from the storm will spread across Nova Scotia and even into PEI and Southern New Brunswick, with rainfall totals at this point expected to be in the 5-30mm range across the region for Monday. Exact amounts and locations will become clearer by this time tomorrow. Since the storm will be passing so far offshore, winds will not be a concern in the Maritimes.

Newfoundland, particularly the Burin and Avalon Peninsulas, will get hit harder than the Maritimes since Ernesto will be passing much closer. Southwest-facing coastlines can expect to begin seeing the ocean swell from the storm beginning late Sunday with large waves and hazardous surf starting late Monday and continuing into Tuesday. These waves and the storm surge will likely result in coastal flooding along these southwest-facing shores. Since Ernesto is expected to pass close to the Avalon late Monday, the winds won’t be as strong on land as they will be closer to the centre of the storm. Nonetheless, wind gusts of up to 100km/h can be expected along the southern shores of the Avalon, especially from Saint Vincent’s to Cape Race, and weakening further inland. Rainfall will be heavy for a brief period of time late in the day Monday for Eastern Newfoundland, including into Bonavista. Light rain will spread across the rest of the Island ahead of the storm Monday afternoon. It is still a bit too early to predict exact totals, but at this point the Avalon could see 30-50mm of rain in a 6 hour period.

Model Forecast Tracks for Hurricane Ernesto, Courtesy of Tomer Burg.

While the track of Ernesto through Atlantic Canada has become clearer, the intensity at which it will travel through the region appears to have also become clearer. The Canadian Hurricane Centre predicts that Ernesto will maintain hurricane strength up to its final approach of Newfoundland, with winds of 120km/h, which is just above the threshold for a storm to be considered a hurricane. Then, just as it passes south of the Avalon, it will transition to a post-tropical storm.

Previous forecasts from the CHC/NHC showed that Ernesto would weaken somewhere between being offshore of Nova Scotia and around the Avalon, with no indication of where this transition may take place. This has now become clearer now that the storm has passed over Bermuda. Ernesto will experience a decrease in shear, giving the storm a chance to recover from ingesting so much dry air and it will undergo a short period of restrengthening tomorrow before hitting the point in which sea surface temperatures drop below 26°C and it begins to lose fuel. The image below shows that wind speeds at the storm’s centre will increase between Hour 24 and Hour 48, indicating this window of restrengthening. As a result of this strengthening in the storm, it will then take a bit longer to weaken to a post-tropical storm and it will maintain its status as Category 1 Hurricane deeper into Canadian waters. We will continue to monitor the storm and we will have our own rain and wind forecasts coming later tomorrow.

Forecast Track and Intensity of Hurricane Ernesto with Sea Surface Temperatures, courtesy of Tomer Burg.

Wet & Unsettled Weekend Brings Threat of Severe Storms and Significant Rainfall to Southern Ontario

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As we approach the final weeks of summer, with the back-to-school season around the corner and the arrival of astronomical autumn just under a month away, it seems Mother Nature is continuing the trend of a wet summer. The upcoming weekend is set to bring multiple rounds of rainy weather, and by early next week, we might even get a taste of early fall-like conditions, with possible single-digit lows for parts of Southern Ontario.

Rain over the next few days will come in waves, starting Friday afternoon in Southwestern Ontario and lingering through the weekend. Thunderstorm activity will play a significant role in this weekend’s rainfall, potentially leading to localized totals approaching 80mm. The rain should taper off by early Monday, with Eastern Ontario seeing the last of the precipitation.

MODEL IMAGE FROM WEATHERBELL

As of Friday afternoon, the first wave of rain is already moving into Southwestern Ontario, extending into regions around Lake Huron and Georgian Bay. This cluster of rain and embedded thunderstorms is expected to gradually track eastward into the Golden Horseshoe and Central Ontario by Friday evening.

Rainfall amounts will be highly variable due to the thunderstorm component, but widespread totals of 5-15mm are expected by Saturday morning. Localized amounts could reach 25-50mm for areas that experience thunderstorm activity, though it’s difficult to pinpoint exactly where this will occur.

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Moving into Saturday, the rain will become less widespread, with a focus on Eastern Ontario and Southwestern Ontario during the morning hours. Eastern Ontario is expected to see lingering precipitation from Friday night’s first wave of rain.

We are also closely monitoring the risk of pop-up thunderstorms in Southwestern Ontario, extending into the Golden Horseshoe through late morning and early afternoon on Saturday. While these storms are expected to be mostly non-severe and primarily a rainfall risk, we can’t rule out a marginal severe threat, as the environment could potentially support some hazards, including hail and damaging wind gusts. An isolated tornado can’t be ruled out, though the risk is relatively low.

MODEL IMAGE FROM WEATHERBELL

More isolated pop-up thunderstorms are expected across Southwestern Ontario, the Golden Horseshoe, and Central Ontario throughout Saturday afternoon and evening. There is concern that these storms will be slow-moving, with some areas experiencing multiple rounds of storms in a short time frame. This could lead to a heightened flash flooding risk, particularly in more urban parts of Southern Ontario, such as the Greater Toronto Area.

Due to the localized nature of the rain on Saturday, some areas may not see a drop, while others could receive upwards of 50-75mm of rain. The heaviest rain appears to be concentrated along the Hwy 401 corridor between London and Toronto, with other pockets of heavy rain in Central Ontario. However, this is just a general idea from one model and could shift depending on where the storms develop.

There should be a break in the rainfall overnight Saturday for most areas, although a few localized showers are possible, particularly around Southwestern Ontario and the Golden Horseshoe.

MODEL IMAGE FROM WEATHERBELL

Similar to Saturday, pop-up thunderstorms are expected to return across Southern Ontario on Sunday morning and continue throughout the afternoon. These storms could bring additional heavy rainfall to the same regions affected by Saturday’s storms. Again, actual rainfall totals will vary significantly depending on where the storms hit, but some areas could see another 25-50mm (or more) by the end of Sunday.

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We are also closely monitoring the risk of severe storms in Eastern Ontario later in the afternoon and early evening on Sunday. Storms that develop here could bring damaging wind gusts, large hail, and potentially an isolated tornado. It’s still two days away, so much can change, but it appears that the Ottawa Valley, extending along the international border in Eastern Ontario, could see some marginally severe storms.

Rain is expected to continue overnight into Monday morning for Central and Eastern Ontario, with pockets of heavy rain and embedded thunderstorms. Southwestern Ontario and the Golden Horseshoe should finally see the rain taper off by late Sunday evening, with the rain ending in Eastern Ontario sometime Monday morning. This will give way to clear conditions for Monday afternoon and evening.

However, the calm weather will bring much colder air, with overnight temperatures plummeting into the single digits across much of Southern Ontario on Monday and Tuesday nights. Daytime highs will struggle to reach the 20°C mark on Tuesday and Wednesday, making for a much cooler week compared to what we’ve experienced this summer.

Hurricane Ernesto Still on Track to Impact Atlantic Canada; Could Pass Through Newfoundland

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Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 16th at 6Am

Ernesto is continuing to barrel towards Bermuda, now as a Category 2 Hurricane, with wind speeds up to 160km/h. The centre of the storm is expected to pass near or over the island on Saturday while maintaining its strength at a Category 2.

The Canadian Hurricane Centre and the National Hurricane Center have made very little change to their track forecast for Ernesto in the 6am update as it travels northeastward towards Atlantic Canada beyond Bermuda. There is still a large degree of uncertainty since we are still a few days out and this is reflected in the size of the cone on the forecast map.

Individual weather models, on the other hand, have begun to show a western shift. There still are a few models that are more in line with the NHC forecast that keeps Ernesto passing offshore of the Avalon. However, just as many are now suggesting that the storm could pass over the Peninsula instead and one outlier still has it tracking through Central Newfoundland. We may see a change in the official forecasts from the CHC and NHC that reflects this western shift in the models.

There is definitely more agreement in the path of Ernesto as it passes offshore of Nova Scotia on Monday. The amount of rain it brings to the Maritimes will be entirely dependent on just how far offshore it stays. Nova Scotia will most likely see rain, but if the storm passes closer to the province, we could see rain move into New Brunswick and PEI as well. Given its offshore track, strong winds likely won’t be much of an issue, but pounding surf is expected to begin for the Atlantic Coast of Nova Scotia ahead of the storm on Sunday and continuing until after its passing on Tuesday.

The exact impacts to Eastern Newfoundland will be entirely dependent on the path that Ernesto takes either around or through the province. The strongest winds will be found around the centre of the storm and at that point in the storm’s life, gusts are projected to be around 110km/h so hopefully it will stay offshore. Rainfall across the province will also vary, with higher amounts expected closer to the middle of the storm. These impacts will become clearer once there is more consensus in the track. The hazardous surf will hit south-facing shores of Newfoundland beginning late Sunday and large waves should impact the Avalon and Burin Peninsulas throughout the day Monday. The large waves, combined with storm surge. could result in coastal flooding so be sure to exercise caution in these areas.

Model Forecast Tracks for Hurricane Ernesto, Courtesy of Tomer Burg.

Ernesto strengthened into a Category 2 late yesterday and further strengthening stalled overnight, despite being in warm water, likely due to continued ingestion of dry air. It is expected to continue to strength through today, but that could be limited by an increase in wind shear, which works against hurricanes. At this point, Ernesto will top out at a Category 2.

Hurricane Ernesto will begin to lose strength after it hits Bermuda and pushes northward into cooler waters and experiences increased shear. It will enter Canadian waters as a weak Category 1 Hurricane and it should rapidly weaken into a post-tropical storm as it approaches Newfoundland mostly due the much cooler sea surface temperatures, but also even more wind shear. Hurricanes need water temperatures of at least 26°C to survive and Ernesto will lose that as it tracks into Atlantic Canada. Nonetheless, winds at the centre of the storm are still expected to be in the 110-150km/h range as it moves through the region.

Forecast Track and Intensity of Hurricane Ernesto with Sea Surface Temperatures, courtesy of Tomer Burg.

Hurricane Ernesto Likely to Impact Atlantic Canada; Uncertainty Looms on Exact Track

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Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 15th at 12pm

Hurricane Ernesto is currently a Category 1 Hurricane and is still moving northeastward towards Bermuda. While it is fairly certain that the island nation will take a direct hit from the storm, its track as it continues northward into Canadian waters is much more uncertain.

In the 12pm update from the Canadian Hurricane Centre, in conjunction with the National Hurricane Center in the US, Ernesto is still expected to have some sort of impact to the Maritimes and Newfoundland, despite the uncertainty in the exact track.

Guidances from different individual weather models, as shown below, indicate potential paths that the centre of the storm may take over the next few days. In some cases, the storm may stay well offshore and only sideswipe Newfoundland with heavy rain and wind while missing the Maritimes completely. On the other hand, one model has the storm tracking straight though Central Newfoundland, which would not only greatly impact the island, but this track would also bring rain and wind further west into the Maritimes.

However, we are starting to see some agreement between some of these models that would see Ernesto stay well offshore of Nova Scotia, with only a bit of rain hitting the province, before passing just south of the Avalon Peninsula, bringing strong winds and heavy rain to Eastern Newfoundland and strong surge to coastal areas across Atlantic Canada. The swells are expected to arrive in the Maritimes beginning Saturday, with more dangerous surf starting Sunday, ahead of the storms arrival to the region early Monday.

Model Forecast Tracks for Hurricane Ernesto, Courtesy of Tomer Burg.

So what are we looking at strength wise? Ernesto is currently a Category 1 in 29°C waters. This sea surface temperature will certainly help the storm strengthen, however, dry air is being pulled into the centre of the storm which is limiting its organization. The warm waters and dry air, combined with some moderate vertical shear (which needs to be low in order for a hurricane to survive and strengthen), means that Ernesto will strengthen to a strong Category 2 Hurricane.

As the storm continues to travel north-northeastward beyond Bermuda, it will encounter cooler waters and shear will increase, which will work to weaken it back down to a Category 1. As it moves into Canadian waters, the sea surface temperatures fall below 26°C. This is the magic number for hurricane development and growth so at this point, it will weaken even further. Ernesto expected to travel through the region starting as a low-end Category 1 and weakening to a post-tropical storm, with winds in the centre of the storm in the range of 110-150km/h.

Forecast Track and Intensity of Hurricane Ernesto with Sea Surface Temperatures, courtesy of Tomer Burg.

Slight Risk for Severe Storms in Southern Saskatchewan for Tuesday into Wednesday

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In a repeat of Monday, storms will be likely in Saskatchewan again Tuesday and continuing into early Wednesday. This time, however, the threat has increased to a slight risk across a large swath of Southern Saskatchewan which could see as much as 100mm of rain, the occasional wind gust exceeding 90km/h, up to toonie-size hail and the possibility of an isolated tornado.

The initial storm activity is anticipated to start mid-afternoon Tuesday in the west with some isolated cells, but things will begin to ramp up as we approach the evening hours. This is when we expect these individual storm cells to begin to merge, creating clusters of storms that will push eastward across the southern half of the province throughout the evening and overnight and into the early morning hours of Wednesday.

The main threat from these storms will be the hail, with up to toonie-size likely, as well as wind gusts that could reach 100km/h. There is also the possibility of training thunderstorms, multiple storms that follow the same track, so flooding will be a concern as some areas could see up to 100mm of rain in only a few hours. It seems unlikely based on the data, but an isolated tornado can not be completely ruled out.

Post-Tropical Depression Debby Will Bring Up to 50mm to New Brunswick, Lesser Amounts to Nova Scotia and PEI Over the Weekend

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After tracking the shifts in the potential path for Tropical Storm Debby over the past few days, the storm will finally make its way into the Maritimes beginning Friday morning with the outer bands of rain. Thankfully, the impacts of this storm will be limited, as opposed to some of the late season post tropical storms we’ve seen in the recent past, like Fiona two years ago.

Rain will move into the region from the southwest beginning mid-morning Friday as light showers. Steady light rain can be expected across Nova Scotia and Prince Edward Island throughout much of Friday and Saturday and into Sunday morning.

The precipitation, however, will intensify to heavy rain in Northern and Western New Brunswick starting Friday afternoon and continuing into Saturday afternoon before starting to taper off. This area of heavier rain will coincide with the path of the center of the storm as it tracks through the region. The Canadian Hurricane Centre’s track forecast from 6pm Thursday is included below. Embedded thunderstorms are expected from the remnants of Debby and this will likely locally increase rainfall totals closer to 50mm along the western edge of the province.

Winds are expected to increase across the entire region in the early morning hours Saturday and lasting for approximately 18 hours before calming. Gusts are expected to top out in the 70-80km/h range, not nearly as strong as we’ve seen in past post-tropical storms.

The Canadian Hurricane Centre Track Forecast for Debby Issued on August 8, 2024 at 6pm ADT

Debby to Bring Flooding Threat to Parts of Southern Ontario on Friday With Up to 50-100mm of Rain Possible

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After making landfall in Florida earlier this week, what was Tropical Storm Debby has brought significant rainfall along the US East Coast. Now a post-tropical system, Southern Ontario is on track to feel the effects of the remnants of Debby over the next few days.

Significant rainfall is in the forecast with a particular focus on Eastern Ontario, which could see up to 100mm by the end of the week. This is not what many across Southern Ontario will want to hear, considering this year's unusually wet summer.

There is still some uncertainty about the exact track of the system, as it won’t arrive until Friday. A more eastern track would shift the heavier rain across the border into the Northeastern US and Quebec.

On the other hand, if the system tracks further to the west, we could be talking about more widespread significant rainfall totals, potentially extending into Central Ontario and the Golden Horseshoe. Hence, it’s important to note that the forecast may change as we get closer to the arrival of the system.

MODEL IMAGE FROM WEATHERBELL

At this point, we are expecting to see some isolated pop-up showers and non-severe thunderstorms develop throughout the day on Thursday across Southern Ontario. This is in advance of the system on Friday, which is when we expect the bulk of the rainfall to occur.

Due to the localized nature of these storms, the rainfall totals will be extremely variable, ranging from a few millimetres to up to 15-20mm in the heaviest pockets by the end of Thursday.

MODEL IMAGE FROM WEATHERBELL

One thing we are closely monitoring is the potential for a persistent band of precipitation with embedded thunderstorms to develop late Thursday and carry into Friday. Current data suggests it will set up somewhere around Woodstock/Kitchener, stretching across Lake Simcoe and into Central Ontario.

This line could produce locally significant rainfall totals overnight and Friday morning as it essentially locks in place as the remnants of Debby approach from the southeast. Keep in mind that this line could shift and will be extremely localized, so not everyone will see the heavy rain. Local rainfall totals could approach 25-50mm by Friday morning, perhaps even higher if a particular area sees multiple rounds of thunderstorms.

The precipitation associated with the system is expected to spread across Eastern Ontario by Friday morning, which is when we expect to see the bulk of the forecasted rainfall. This will only heighten the flooding threat since it will all happen within the span of a few hours.

In addition to the rain, we are also likely to see some embedded thunderstorm activity within the bands of precipitation throughout the morning and afternoon on Friday.

These storms should stay mostly non-severe, but we’ve seen in the past that these tropical systems have a tendency to present a tornado threat, especially along the western side of the system, which is where Southern Ontario will be positioned.

This is certainly not a guarantee for tornadoes, but we will be closely watching this aspect of the system and will issue a more detailed forecast if it becomes more likely.

MODEL IMAGE FROM WEATHERBELL

Rain is expected to taper off in the west through Central Ontario into the Golden Horseshoe by early afternoon on Friday. For Eastern Ontario, heavy rain is expected to continue throughout the afternoon and early evening hours on Friday.

We should begin to see some clearing in the west by dinner time, with the rain finally coming to an end around midnight for the Ottawa Valley and those along the St. Lawrence.

As we’ve mentioned, the highest impact of this system is expected in Eastern Ontario, which will be closest to the track of the system. Rainfall totals are likely to generally range from 50-100mm, but some localized pockets could even exceed the 100mm mark based on some of the latest model data.

It is important to keep in mind that thunderstorm activity will play a big role in the rainfall totals, so the actual totals could vary significantly between locations. That’s why we have a large range of 50mm - it’s hard to nail down the exact totals due to the localized nature of thunderstorms.

The forecasted rainfall totals drop off quite fast once you head further west. We are projecting between 25 to 50mm of rain for the Golden Horseshoe and parts of Central Ontario around Lake Simcoe.

At this point, we are expecting 15-30mm of rain for the Greater Toronto Area (GTA) along the Lake Ontario shoreline into the Niagara region. That could change if that line of rain overnight Thursday shifts into the GTA, as the latest models suggest should develop just to the northwest.

Less than 20mm of rain is expected for Southwestern Ontario, with even lower totals for Deep Southwestern Ontario, which may see barely a drop of rain from this system.