Northern Ontario: Thunderstorm Outlook for Friday, June 11, 2021

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Forecast Discussion

A questionable risk of storms exists for Northwestern Ontario along the Manitoba border which may see storms enter the province from Manitoba and Minnesota later in the day on Friday. The exact strengthen of these storms is currently unclear and depends on the timing. If they show up too late in the night then it will bring just a non-severe nocturnal thunderstorm risk.

Northern Ontario: Thunderstorm Outlook for Thursday, June 10, 2021

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Forecast Discussion

A decaying cluster of thunderstorms that brought severe weather to parts of Manitoba and Northwestern Ontario late Wednesday is expected to continue to track eastward through the region overnight into Thursday morning. The environment is no longer favourable for these storms to remain severe so these nocturnal storms should be non-severe with small hail, strong wind gusts and heavy rainfall. They’ll reach Northeastern Ontario to the east of Lake Superior during the early morning as they slowly fizzle out by the afternoon hours. Widespread rainfall amounts between 25-50mm are possible within this line of storms so isolated flooding could be an issue. As mentioned, the storm threat will come to an end by late morning on Thursday.

Northern Ontario: Thunderstorm Outlook for Thursday, June 10, 2021

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Forecast Discussion

Non-severe thunderstorms expected to cross into the province late Wednesday will continue to track across the province during the early hours of Thursday. These storms won’t be particaully strong and should fizzle out later in the morning. The main risk is some strong wind gusts, small hail and heavy rainfall along with frequent lightning strikes.

Northern Ontario: Thunderstorm Outlook for Wednesday, June 9, 2021

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Forecast Discussion

Severe thunderstorms are expected to develop over central and western parts of Manitoba during the afternoon and evening hours of Wednesday. These storms will cross into Northwestern Ontario sometime late in the evening with the main threat being damaging wind gusts and large hail. There is also a marginal tornado risk with the storms, but it appears that the tornado risk will be highest over Manitoba in the early lifespan of the storms. The storms will continue to track eastward throughout the evening and into the overnight hours although they’ll begin to weaken and should be fully non-severe by midnight once they reach Thunder Bay and regions around Lake Superior. Non-severe thunderstorms are possible for Northeastern Ontario early in the morning on Thursday although this will be covered in Thursday’s thunderstorm outlook.

Southern Ontario: Thunderstorm Outlook for Wednesday, June 9, 2021

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Forecast Discussion

A cluster of slow-moving thunderstorms could develop through parts of Southwestern Ontario during the afternoon and early evening on Wednesday. These storms will be similar to what we’ve seen over the past few days so they should be the typical garden variety non-severe storms. However, due to the slow-moving nature of these storms, it could produce some localized flooding if a region gets stuck under one of these cells for a few hours. The main area of concern for this flooding potential is through the London, K/W and Brantford area along with Huron and Perth counties. This is where the latest data indicates most of the storms will develop although this zone may shift around depending on how the environment materializes. Storms will quickly fizzle out after sunset once the daylight heating that was fuelling them disappears.

Northern Ontario: Thunderstorm Outlook for Wednesday, June 9, 2021

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Forecast Discussion

There could be some thunderstorm activity along the Manitoba border in Northwestern Ontario with non-severe storms during the morning and some more potential severe storms developing in Southeastern Manitoba and tracking into Northwestern Ontario during the evening hours on Wednesday. It is unclear exactly how strong these storms could be and the timing which could have a huge influence if the worst stays in Manitoba or is able to cross over the border.

Northern Ontario: Thunderstorm Outlook for Tuesday, June 8, 2021

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Forecast Discussion

Thunderstorms related to severe weather on late Monday across Minnesota are expected to reach the international border around Fort Frances overnight and into Tuesday morning. By the time the storms reach Ontario they’ll be quite weak so severe weather is unlikely. The main risks with these storms are some strong wind gusts, heavy rainfall and lots of lightning. They will quickly die out over Lake Superior during the late morning. Another round of storms should develop later in the day through the afternoon and evening hours east of Lake Superior in southern parts of Northeastern Ontario. One or two of these storms could bring some severe weather including damaging wind gusts, sizable hail and heavy rainfall. Flash flooding will be a major concern since these storms will be moving slowly and could easily dump 50-100mm over a location within a few hours. The storm threat will come to an end after sunset.

Southern Ontario: Thunderstorm Outlook for Wednesday, June 9, 2021

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Forecast Discussion

Another day of slow-moving pop-up thunderstorms is expected during the afternoon and evening hours on Wednesday for a small area stretching from Sarnia through London and around the GTA. The latest data indicates the strongest potential for the storms around in the Huron/Perth counties and K/A area. There could also be a flooding threat due to the slow-moving nature of the storms with localized rainfall totals over 50mm.

Southern Ontario: Thunderstorm Outlook for Tuesday, June 8, 2021

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Forecast Discussion

Two rounds of thunderstorms are expected to affect Southern Ontario on Tuesday starting with a cluster of storms developing around the London area during the early morning hours and tracking through the GTA during the mid to late morning. These storms will be non-severe but they could be moving quite slowly and like with the storms we saw on Monday, flooding could be an issue with localized rainfall amounts exceeding 50mm. The second round will occur during the afternoon and evening hours with pop-up storms developing around the Golden Horshoe into Southwestern Ontario along with another zone in Northeastern Ontario including Sudbury, North Bay and Algonquin Park. Any storms that develop will again pose a flooding threat along with some small to moderate size hail. The environment is much stronger up towards Northeastern Ontario which is why we’ve included an isolated severe risk for this area due to stronger wind gusts and sizable hail. Storms will quickly fade out after sunset and the daylight heating that was fueling them disappears.

Northern Ontario: Thunderstorm Outlook for Tuesday, June 8, 2021

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Forecast Discussion

A decaying complex of non-severe thunderstorms is expected to move into Northwestern Ontario around the Fort Francis area from Minnesota during the early morning hours on Tuesday. These storms will be slowly weakening as they track eastward along the International border through Thunder Bay and regions around Lake Superior throughout the late morning. It will likely fade out before reaching Northeastern Ontario, but the environment is favourable for storm development throughout southern parts of Northeastern Ontario such as Sault Ste. Marrie, Timmins and Sudbury during the afternoon and evening. Not all models show storms developing despite the high instability although if they do fire up, there is a questionable severe risk with the storms that develop. We may need to upgrade some areas to the isolated severe risk category if storm development is looking more likely.

Southern Ontario: Thunderstorm Outlook for Tuesday, June 8, 2021

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Forecast Discussion

Widespread scattered thunderstorms are expected to affect Southern Ontario starting with a round of storms early in the morning for Southwestern Ontario and into the Golden Horseshoe. Another round will develop later in the day throughout the region bringing the potential for mostly non-severe wind, hail and rainfall. There is also some questionable severe risk mainly through Northeastern and Eastern Ontario where high instability exists (shown in the ‘questionable severe risk’ zone), but storm development appears to happen further south where the environment is less favourable. At this point, we’re sticking with a non-severe risk but some areas may need to be upgraded to an isolated severe risk if storm development in the area with the stronger environment is looking more likely.