Rapidly Strengthening Bomb Cyclone Expected to Bring Heavy Rain and Wicked Winds to the Maritimes

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Hang on to your umbrellas! We have an incoming bomb cyclone that is set to not only drench the Maritimes, but bring some intense winds to the region as well. A bomb cyclone is a storm that undergoes rapid intensification, called bombogenesis, that results in a drop in central pressure of at least 24mb over a 24 hour period. A system has begun travelling northward along the American Atlantic Coast and the further north it travels, the stronger it is expected to become under this rapid intensification.

The storm will bring precipitation to the Maritimes in two rounds. It will start off with warm, moisture-laden air being funnelled up from the Gulf along the warm front, leading to temperatures climbing into the double digits. Following a break in the precipitation from the first round, the length of which will be dependent on the distance from the centre of the storm, a second round of rain will move in along the cold front. Behind this cold front, temperatures are expected plummet and will fall below 0°C across New Brunswick, leading to the risk of a flash freeze. Combined, these two rounds of rain will bring a widespread 10-50mm of rain across most of the Maritimes.

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New Brunswick

Things in New Brunswick will certainly get messy over the coming days due to this incoming storm. The first wave of precipitation will move into Western New Brunswick around sunrise Wednesday morning. The temperatures will rise with the arrival of the warm front and rain, but there will still be some isolated pockets of cold air near the surface that could persist for several hours, leading to freezing rain. Luckily any ice accretion will quickly melt as temperatures rise.

The rain will continue throughout most of the day and it will start to taper off, from south to north beginning in the evening. Due to its proximity to the centre of the storm, there won’t be a break between to the rounds of precipitation in Northwest New Brunswick. As a result, this is where the highest rainfall amounts of close to 50mm are expected. The rest of the province will start to see this second wave move in from the west overnight. It will lose intensity as it pushes eastward and the heaviest rain will fall over the western half of the province, where 25-50mm of rain is expected overall with the storm and only 10-25mm to the east. This second round won’t last long and will exit the province by the late morning.

There will be a unique problem in New Brunswick that the rest of the Maritimes won’t have to worry about. Some parts of the province have a considerable snowpack over 30cm which will end up melting with temperatures rising into the double digits through the day Wednesday. However, when combined with the amount of incoming precipitation and the ground likely remaining at least partially frozen, standing water and flooding becomes a concern. To make matters worse, the temperatures will drop drastically across most of the province overnight Thursday, to well below the freezing mark, which could lead to a widespread flash freeze.

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Nova Scotia

The scenario across Nova Scotia with this storm will be a little less complicated, in regards to precipitation. The first wave of rain will make its way into Western Nova Scotia in the mid to late morning Wednesday. The rain will be heavy at times across the western half of the Mainland and it will then dissipate across the province through the evening. The second round of rain will then arrive early Thursday morning and is only expected to last 4 hours or so as it crosses the province, before the storm finally makes its way out of the region in the evening. Most of Mainland Nova Scotia and along the South Coast of Cape Breton Island can expect 10-25mm of rain while the rest of the province will see 5-10mm

Prince Edward Island

Prince Edward Island, much like Nova Scotia, has a fairly straightforward forecast with this storm. The first wave of rain will impact the Island starting early Wednesday afternoon and continuing into the evening. Then, the second wave will move in after sunrise on Thursday and cross the Island in the span of 3-4 hours. Rainfall amounts of 10-25mm are likely in Prince and the western half of Queens County and 5-10mm in Kings County and the eastern half of Queens County.

Strong winds will also be a factor with the incoming bomb cyclone. In this model image showing 1:00 AM Thursday, we can get a good look at both the size and structure of the storm, along with the precipitation types and their intensities. What we also see is the projected internal pressure of the storm, in millibars, as well as the lines of equal pressure, in black, known as isobars. Winds are driven by air moving from areas of high pressure to those of low pressure and when isobars are really close in strong storms, as seen in this case, we know that the winds will be quite strong.

The strong winds will start making their way into the Maritimes Wednesday evening and they will peak overnight. The entire region will get hit by sustained winds above 40km/h and gusts over 70km/h, but Western Nova Scotia and Southwest New Brunswick in particular will be hammered by gusts in excess of 100km/h. These will be onshore winds so pounding surf and some coastal flooding are very likely along the Atlantic Coast of Nova Scotia and along the Fundy Coast to the west of St. John starting late Wednesday and continuing through Thursday morning.

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.

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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.

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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.

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

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.

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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

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.

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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.

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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.

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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.

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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.

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.

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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

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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.

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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.

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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.

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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.

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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.