ONTARIO: Thunderstorm Forecast for Saturday, July 8, 2023

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FORECAST DISCUSSION

There is the risk of non-severe thunderstorms in Deep Southwestern Ontario extending into regions east of Lake Huron. Thunderstorms are expected to develop over Michigan and may cross into Ontario sometime during the afternoon and early evening on Saturday. These storms should be fairly weak, however, there is a very questionable risk for strong storms toward the Windsor, Sarnia and Chatham regions.

The strongest environment for severe activity is expected to remain south of the border, but it isn’t out of the question that one of these storms sneak across the border. Although the confidence is too low for us to introduce an isolated severe risk.

NORTHERN ONTARIO: Thunderstorm Forecast for Saturday, July 8, 2023

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FORECAST DISCUSSION

Thunderstorms are currently not expected across Northern Ontario on Saturday.

ONTARIO: Thunderstorm Forecast for Friday, July 7, 2023

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FORECAST DISCUSSION

Thunderstorms are currently not expected across Southern Ontario on Friday.

NORTHERN ONTARIO: Thunderstorm Forecast for Friday, July 7, 2023

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FORECAST DISCUSSION

A line of thunderstorms is expected to sweep across Northwestern Ontario during the afternoon on Friday. A few of these storms may become severe with up to quarter-sized hail, 90 km/h wind gusts and heavy rainfall. An isolated tornado can’t be ruled out either.

ONTARIO: Thunderstorm Forecast for Thursday, July 6, 2023

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FORECAST DISCUSSION

On Thursday, a cold front is forecasted to sweep across Southern Ontario, bringing the risk of thunderstorms. During the early afternoon, a line of storms is expected to develop along the front, starting from Georgian Bay and extending southwest towards London. Throughout the afternoon and early evening, the line will track eastward.

Considering the environment, there is potential for these storms to become severe. The strongest threat zone will be through Southwestern Ontario and into parts of Central Ontario including Simcoe County and Muskoka. Storms here could bring the potential for up to toonie-sized hail, 100 km/h wind gusts and heavy rainfall. One or two tornadoes are also possible (see below).

The rest of Southwestern Ontario and the Golden Horses can expect an isolated severe threat. Storm threats include 90 km/h wind gusts and quarter-sized hail.

Tornado Risk

Tornado risk on Thursday will be focused on a very similar area as last week stretching from around the Southern shoreline of Georgian Bay through Muskoka and into Algonquin Park. Models indicate that multiple isolated storms could develop over this region and combined with the prime environment, may produce one or two tornadoes.

An isolated tornado threat exists in surrounding areas including Southwestern Ontario and through parts of the GTA.

NORTHERN ONTARIO: Thunderstorm Forecast for Thursday, July 6, 2023

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FORECAST DISCUSSION


The North Bay and Sudbury region faces the risk of severe thunderstorms as isolated storms develop over Georgian Bay in the afternoon and track into the area. The highest risk is concentrated in the southeastern tip of Northern Ontario, particularly in North Bay. In this area, there could be threats of 100 km/h wind gusts and hail the size of toonies. While an isolated tornado cannot be ruled out.

Moving further west, Sudbury and Englehart also have an isolated risk of severe weather, including 90 km/h wind gusts and hail the size of quarters.

ONTARIO: Thunderstorm Forecast for Thursday, July 6, 2023

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FORECAST DISCUSSION

On Thursday, a cold front is forecasted to sweep across Southern Ontario, bringing the risk of thunderstorms. During the early afternoon, a line of storms is expected to develop along the front, starting from Georgian Bay and extending southwest towards London. Throughout the afternoon and early evening, the line will track eastward.

Considering the environment, there is potential for these storms to become severe. The main threat associated with them will be damaging wind gusts exceeding 90 km/h. Although not the primary concern with this storm mode, there is also a possibility of nickel to quarter-sized hail. Additionally, an isolated tornado cannot be ruled out.

However, there is some uncertainty regarding the timing and the exact strength of the environment. Therefore, at this point, we are maintaining an 'isolated' risk. After reviewing the latest data, we may consider upgrading some areas to a 'slight' risk in our update on Wednesday evening.

ONTARIO: Thunderstorm Forecast for Wednesday, July 5, 2023

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FORECAST DISCUSSION

Thunderstorms are currently not expected across Southern Ontario on Wednesday.

NORTHERN ONTARIO: Thunderstorm Forecast for Wednesday, July 5, 2023

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FORECAST DISCUSSION

Scattered thunderstorms are expected to develop across Northeastern Ontario during the afternoon on Wednesday. Some of these storms could become severe around the Chapleau, Timmins and Cochrane regions. The main risks will be up to quarter-sized hail, 90 km/h wind gusts and maybe even an isolated tornado. This severe risk will diminish by the evening as the line of storms slowly weakens.

ONTARIO: Thunderstorm Forecast for Tuesday, July 4, 2023

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FORECAST DISCUSSION

A few isolated pop-up thunderstorms are possible in Eastern Ontario during the afternoon and early evening on Tuesday. Based on the environment, it may allow for one or two storms to briefly become severe with nickel-sized hail, 90 km/h wind gusts and heavy rainfall. However, these storms will be extremely localized and most of those in Eastern Ontario will stay dry. The highest chance for storms will be around the Quebec border east of Ottawa.

NORTHERN ONTARIO: Thunderstorm Forecast for Tuesday, July 4, 2023

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FORECAST DISCUSSION

Thunderstorms are currently not expected across Northern Ontario on Tuesday.

ONTARIO: Thunderstorm Forecast for Monday, July 3, 2023

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FORECAST DISCUSSION

Scattered non-severe thunderstorms are possible across Southern Ontario on Monday afternoon and evening. The thunderstorm activity will be more concentrated around Georgian Bay and along the northern shoreline of Lake Ontario. There is also a secondary risk zone in Deep Southwestern Ontario. We may see the potential for funnel clouds which in rare cases can produce landspout tornadoes.

NORTHERN ONTARIO: Thunderstorm Forecast for Monday, July 3, 2023

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FORECAST DISCUSSION

A decaying line of thunderstorms is expected to cross into Northwestern Ontario from Manitoba just after midnight during the early hours of Monday morning. There is an isolated severe risk associated with this line, but the timing should limit the overall severe threat to 90 km/h wind gusts and quarter-sized hail.

Later on Monday, there is an additional severe risk to the east around Armstrong and west of Thunder Bay. An isolated tornado can’t be ruled out. Non-severe storms are also possible around the Quebec border in Northeastern Ontario.

ONTARIO: Thunderstorm Forecast for Sunday, July 2, 2023

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FORECAST DISCUSSION

Isolated non-severe thunderstorms are possible during the afternoon and evening on Sunday. The potential for storms stretches through Southwestern Ontario through the Golden Horseshoe and into Extreme Eastern Ontario. There is some indication that the environment could be favourable for the development of funnel clouds in Southwestern Ontario. While funnel clouds don’t usually pose a risk to the ground, in rare cases they can touch down and become a landspout tornado.

NORTHERN ONTARIO: Thunderstorm Forecast for Sunday, July 2, 2023

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FORECAST DISCUSSION

Thunderstorms are currently not expected across Northern Ontario on Sunday.

ONTARIO: Thunderstorm Forecast for Saturday, July 1, 2023

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FORECAST DISCUSSION

During the afternoon on Saturday, scattered thunderstorms are forecasted to develop in a line extending from Petawawa through Lake Simcoe and into the northern Greater Toronto Area (GTA). This line of storms will then track southeastward, with conditions favouring the potential for some of these storms to become severe.

A slight risk for severe weather exists in areas around Ottawa, Renfrew, and Peterborough. The main threats associated with these storms include wind gusts reaching 100 km/h, hail up to the size of a loonie, and heavy rainfall. While the possibility of an isolated tornado cannot be ruled out, the risk is questionable.

Surrounding regions, including the rest of Eastern Ontario and the GTA, have an isolated risk of severe weather.

NORTHERN ONTARIO: Thunderstorm Forecast for Saturday, July 1, 2023

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FORECAST DISCUSSION

Scattered non-severe thunderstorms are possible during the afternoon and evening in Northeastern Ontario. The highest chance of storms will be along the Quebec border. At this time, it doesn’t appear that these storms will present any severe threats. Small hail, strong wind gusts and heavy rainfall are still possible with any of the storms.

NORTHERN ONTARIO: Thunderstorm Forecast for Friday, June 30, 2023

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FORECAST DISCUSSION

Scattered thunderstorms are expected to develop across Northeastern Ontario on Friday afternoon. A few of these storms could become severe in a zone stretching from North Bay through Timmins and into Kapuskasing. The main risks are 100 km/h wind gusts, quarter to toonie-sized hail and an isolated tornado threat.

ONTARIO: Thunderstorm Forecast for Friday, June 30, 2023

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FORECAST DISCUSSION

During the mid to late afternoon on Friday, several isolated storms are expected to form in a line extending from North Bay southwestward to Southwestern Ontario.

Based on the latest model data, the environment these storms will encounter suggests the potential for some to become severe. The main risks associated with these storms include large hail ranging from toonie to golf ball size and wind gusts of up to 100 km/h. The possibility of one or two tornadoes cannot be ruled out, as discussed below.

As the evening approaches, the storms are expected to rapidly weaken as the supportive environment diminishes. However, some strong winds could still affect parts of Eastern Ontario and the Golden Horseshoe.

Severe weather is also possible in Southwestern Ontario, although the exact location of storm development remains uncertain according to current model data. It is more likely to be concentrated in the Georgian Bay and Central Ontario areas during the later afternoon

TORNADO RISK

The highest risk for tornadoes associated with these storms is forecasted to stretch from Orangeville through Simcoe County and into Muskoka. This region carries the potential for one or two tornadoes. There is also an isolated tornado risk for the rest of Southwestern Ontario and its surrounding areas.

ONTARIO: Thunderstorm Forecast for Friday, June 30, 2023

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FORECAST DISCUSSION

Friday afternoon and evening will feature a risk of severe thunderstorms extending from Southwestern Ontario to areas around Georgian Bay. Current model guidance suggests the potential development of a line of storms within this risk zone. These storms are likely to be severe, with the primary risks being strong wind gusts and sizable hail. While there is also a tornado risk, it remains uncertain due to the storm mode.

There is a possibility of upgrading the risk level to slight or even strong on Thursday as we gain more confidence in the exact location of the strongest storms. However, models currently disagree on the area of storm development. Therefore, we are maintaining a more widespread isolated risk until we can better determine the specific threat.