Severe Thunderstorm Risk and Heavy Rain to Kick Off the Weekend Across Southern Ontario
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It has certainly been a rollercoaster month for the weather in Southern Ontario! Last week, we experienced near-record-breaking temperatures, giving us a taste of summer. This week, reality hit with chillier temperatures and accumulating snow in some areas. As we approach the weekend, warmer air will return with daytime highs in the upper teens and low 20s on Friday. However, this warmer air brings a risk of thunderstorms and heavy rainfall over the weekend.
The warmth comes from tropical air being pumped into our region from the Gulf of Mexico, but it also carries the threat of rainfall over the next 36 hours across Southern Ontario. Pop-up showers have already begun developing over Michigan and Southwestern Ontario, with rain expected to expand eastward throughout the afternoon and evening, reaching the Golden Horseshoe by dinner time and Eastern Ontario by late evening.
We're also monitoring the risk of a few embedded thunderstorms developing later this afternoon and early evening in advance of this system. The environment is favourable for these storms to become marginally severe, primarily around the Hamilton and Niagara region, extending across the GTA and into Kingston later in the day. Our main concern is large hail up to quarter to loonie size and wind gusts near 90 km/h.
Models consistently show the Niagara region at the highest risk of these storms, so we've given them a slight risk of severe storms. However, this risk is questionable, and we were on the fence between isolated or slight risk zones. We don't expect much of a tornado risk with these storms, but as always, it can't be completely ruled out with any severe thunderstorm.
There's also a questionable risk of a severe thunderstorm on Saturday in parts of Eastern Ontario. At this point, it looks like an isolated risk, and storm development may not even happen. We will be watching and will issue a forecast tonight or early Saturday based on the latest data should severe storms still look possible.
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Aside from the severe risk, this weekend is shaping up to be quite wet across Southern Ontario. Rainfall totals across a wide swath of our region, including London, K/W, Toronto, Barrie, and Muskoka, will range from 15 to 30mm by Sunday morning. This could worsen the flooding experienced in some parts of the province, as is typical during this time of year.
Deep Southwestern Ontario and Eastern Ontario can expect slightly less, with 10 to 20mm of rain anticipated. Scattered showers may linger into Sunday, adding a few additional millimeters of rain in some areas. Remember that with the risk of thunderstorms, localized regions may exceed the forecasted rain and approach 30-40mm.
