Nocturnal Severe Thunderstorm & Tornado Threat for Southwestern Ontario Late Wednesday
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THUNDERSTORM RISK
Confidence is increasing in the potential for an active and stormy night across Deep Southwestern Ontario on Wednesday. A complex of strong to severe storms is expected to develop over Illinois and Michigan in the late afternoon and evening. These storms carry a significant tornado threat, with the Storm Prediction Center in the US placing the Chicago area under a rare 10% significant tornado threat for today.
The environment appears favourable to support the strong cluster of storms as they track across lower Michigan and reach Deep Southwestern Ontario late in the evening. There may even be some isolated storm development ahead of the main line between 8 - 11 PM around Windsor and Chatham.
Both the isolated storms and the complex of storms later in the evening could bring strong severe threats, including large hail up to the size of ping pong balls, wind gusts of 100-120 km/h, and intense rainfall. The Windsor-Essex region faces the strongest tornado risk.
The severe threat will continue into the early overnight hours after midnight, with an isolated severe risk as far north as Goderich and Kitchener, mainly due to the wind threat. Non-severe nocturnal thunderstorm potential will extend northeastward into the Golden Horseshoe and Central Ontario throughout the overnight hours.
tornado RISK
The window of maximum tornado risk is expected to be between 8 PM and 12 AM, spanning Windsor, Essex, and Leamington. If storms arrive before midnight, there is potential for one or two tornadoes, as even a small trigger could result in a spin-up. Conversely, the tornado risk is lower if storms arrive after midnight.
There is an isolated tornado threat from Sarnia through Strathroy, extending into the London region, primarily during the late evening into the early overnight hours.
fLOODING RISK
Apart from Deep Southwestern Ontario, the main concern associated with these storms will be the potential for flooding overnight and into Thursday morning. Current model data suggests a widespread area from Windsor through London, around Lake Simcoe, and the Petawawa region could receive between 50 to 100mm of rain. Localized areas may even exceed 100mm due to thunderstorm activity.
The flooding risk will be isolated and dependent on the track of this cluster of storms. The provided map gives a rough indication of where the heaviest rainfall is anticipated, but the exact track may shift west or east, affecting overall rainfall totals. It is important to be prepared for significant overnight rainfall occurring within a short timeframe.
