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Scattered Severe Thunderstorms to Start October Across Southern Ontario; Isolated Tornado Possible

We are watching the risk for scattered severe thunderstorms across Southwestern and Central Ontario with an isolated risk across Southeastern Ontario. We are also watching the risk of an isolated tornado or two.

Thunderstorm Forecast, for Southern Ontario. Issued October 1st, 2019.
Thunderstorm Forecast, for Southern Ontario. Issued October 1st, 2019.


Areas in yellow and marked with a '3' can expect a moderate risk for severe thunderstorms. The first region in this area extends from Owen Sound over to Midland and Washago extending south towards Woodview, Peterborough, Toronto, Hamilton, and London. This area also includes Sarnia, Kitchener, Niagara, Kincardine, Mount Forest, and the most remaining locations in Southwestern Ontario. Scattered showers and thunderstorms are likely to develop across the Northern throughout Bruce and Grey County and over Southern Michigan. Thunderstorms will converge south and east across Southwestern Ontario forming a line of thunderstorms. As the storms approach Lake Erie and New York State, due to timing, the storms are likely to fall about. The main threats are heavy rain and gusty winds from the front. An isolated tornado is possible but generally unlikely in this area.

The second region in the 'moderate' or yellow area is through Southeastern Ontario extending from Ottawa over to Cornwall, Perth, Brockville, and Kingston. In Quebec, this region includes Gatineau, Montevello, Rigaud and Huntindon. The environment in this region is rather strong, although, models are having a difficult time getting storms developed in that region. If storms develop in this region, an isolated tornado or two, possibly strong, may be possible in this region. Otherwise, heavy rain, gusty winds and small to moderate-sized hail are possible. This area has been placed under an 'area of interest.'

Thunderstorm Forecast, for Southern Quebec. Issued October 1st, 2019.
Thunderstorm Forecast, for Southern Quebec. Issued October 1st, 2019.

Areas in green and marked with a '2' can expect a low risk for severe thunderstorms. This extends from Tobermory over to Parry Sound, Haliburton, Bancroft, Cobden and Sharbot Lake. As described before, thunderstorm development may initiate over this area or slightly further north, allowing time for severe thunderstorms to move in this region. This is increasingly unlikely.

Throughout Eastern Ontario, as stated before, development is lacking on the models despite the rather strong environment. Development is less likely in this region than in the yellow or moderate region, although, it's possible for strong to severe thunderstorms, including an isolated tornado in the 'area of interest'. This region also extends into Quebec and includes Duhamel, Montreal, and Sabrevois.

The second area of low severe weather extends along the Lake Erie shores. As described above, severe thunderstorms will likely begin to weaken before passing over this area bringing a threat of heavy rain and sub-severe wind gusts.

Elsewhere in blue, non-severe thunderstorms are possible.


Following the thunderstorms this afternoon and evening, another round of heavy rain and thunderstorms, possibly sub-severe or isolated severe, will move across Southwestern Ontario from Lake Huron southeast towards Niagara. The main impacted locations extend from Huron County through to Brant County and Niagara Falls.

We will be watching today and update as needed.

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