Rainy Thursday With the Potential for Severe Thunderstorms and Flash Flooding in the Afternoon & Evening Throughout Southwestern Ontario and the Niagara Region
/Valid: Thursday, August 27, 2020
NOTE: The tornado risk zone outlines the region with the highest probability of tornadoes, but tornadoes may occur outside of the zone.
Timing |
Southwestern: 3PM - 12AM
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Not sure what region you are in? Click here for a map showing the regions across Southern Ontario. Northeastern Ontario is north of North Bay (not shown on map).
Thunderstorm Threatcast
Thunderstorm Confidence |
Very High (90%) |
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Severe Confidence |
Low (25%) |
Tornadoes |
Isolated |
Max Wind Gusts |
90+ kmh | 56+ mph |
Max Hail Size |
Quarter |
Max 24-hr Rainfall |
~100 mm | ~4" |
Forecast Discussion
Thunderstorm activity will continue to linger throughout the overnight hours and into Thursday morning as another wave of storms sweeps through Central and Eastern Ontario during the early morning. These storms should remain non-severe although flooding could be a concern particularly in the heavier thunderstorm activity where upwards of 50mm is possible east of Georgian Bay. This nocturnal activity will come to an end by noon as they move across the border and into Upstate New York.
Another round of storms is possible later in the afternoon and into the evening where some of them could reach severe limits, especially with the flooding threat. This threat will be focused on Extreme Southwestern Ontario and along the Lake Erie shoreline although it could make its way into the Western GTA and Niagara region. As mentioned, the flooding threat is the main concern because storms could ‘train’ over a specific location for several hours leading to locally over 100mm of rainfall accumulation. Moderate size hail and strong wind gusts are also possible. The tornado threat isn’t particularly strong but an isolated one can’t be ruled out around the Sarnia, Chatham-Kent and London corridor. The storm threat will end near the midnight hour.
