Heat wave, severe storm threat persists in Ontario, Quebec Thursday
A significant spell of heat and humidity will fuel additional rounds of severe thunderstorms through the day Thursday
A stormy couple of days across Ontario and Quebec will continue into Thursday as a heat wave fuels additional rounds of severe weather across the region.
Pay close attention to watches and warnings in your area. Have a plan in place to act quickly if dangerous thunderstorms threaten your location. Avoid sleeping in rooms where falling trees or tree limbs could pose a hazard.
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Thursday threat builds again over Ontario, Quebec
Days of intense daytime heating have provided two key ingredients for yet another day of severe weather: instability and moisture. Those combined with an approaching cold front will trigger a risk for severe thunderstorms throughout the afternoon and evening hours on Thursday.
The cold front is forecast to slide southward on Thursday afternoon and evening, triggering a line of thunderstorm development along its boundary.
We could see stronger storms with embedded rotation develop northwest of Toronto, around the Guelph area, as well as east of Toronto, around Cobourg.
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The main tornadic threat, however, will be for the Ottawa area, as there is a better chance for wind shear to spin up the storms.
Torrential rainfall will be the primary threat with the high humidity in place. Storms could drop 30-50 mm of rain in a short period of time, which may lead to ponding or flash flooding.
The strongest storms could produce damaging wind gusts of 100 km/h, which may cause tree damage and power outages
Some storms could also produce hailstones 2-4 cm in diameter across the Ottawa Valley and into the Eastern Townships. A non-zero threat for rotation also exists along part of Lake Ontario's north shore and in the Eastern Townships.
There’s considerable uncertainty in the exact location of Thursday’s thunderstorm development with high heat in place and small-scale features acting to trigger the unsettled conditions.