ONTARIO: Thunderstorm Forecast for Friday, May 19, 2023

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MAY 19 UPDATE: The latest data continues to support our previous forecast so it remains unchanged. We may tweak it in the morning or afternoon as needed.

A line of heavy rain with embedded thunderstorms is expected to move across Southern Ontario during the late afternoon and evening hours on Friday. There is the potential for some isolated severe activity in Southwestern Ontario with the primary risks being 90 km/h wind gusts and flash flooding due to ‘training’ storms. The risk for non-severe storms stretches into Central Ontario along with the Golden Horseshoe after the dinner hour on Friday.

Training: Training thunderstorms are a meteorological phenomenon in which multiple thunderstorms continuously form and pass over the same geographical location, following one after the other much like cars on a train track. These storms can be particularly dangerous as they often result in a high amount of rainfall over a relatively small area, leading to a significant risk of flash flooding. The term "training" is used to describe this pattern because the storms typically move along a "track" of atmospheric conditions that are favorable for thunderstorm development, repeatedly impacting the same region.