Possible Severe Thunderstorms on Sunday to End Off a Stretch of Summer-Like Weather Across Southern Ontario This Week

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As the saying goes, 'All good things must come to an end,' and that will become apparent on Sunday as we cap off what has been a stellar week when it comes to the weather. We saw temperatures well into the 20s for multiple days this weekend, which is rare in April. A cold front is expected to slide across the region during the afternoon and evening on Sunday, ushering in much colder air. In addition to providing a sharp drop in temperatures, the front will also spark off another common summer weather phenomenon - thunderstorms!

A line of rain is expected to develop ahead of the front and track across Southwestern Ontario and into the Golden Horseshoe starting just after the lunch hour and continuing throughout the evening. This line will likely have embedded thunderstorms which should remain non-severe for the most part. However, the environment is strong enough to allow an isolated storm to briefly become severe, with the main threat being 90km/h wind gusts and up to pea-sized hail.

The risk zone for the isolated storm includes all of Deep Southwestern Ontario and into the Hamilton/Niagara region. Remember, this is only an isolated risk, and any strong storms will be very localized. Not everyone will see a severe storm tomorrow. Outside of the severe threat, non-severe thunderstorms could deliver heavy rainfall and frequent lightning strikes across much of Southern Ontario. Eastern Ontario could see a few lightning strikes later overnight and pre-dawn Monday, but we didn't include them in the map as this is for Sunday only.

We will continue to monitor the latest data and may update this forecast by early Sunday afternoon if needed. Stay safe!

First "Elevated" Severe Thunderstorm Risk of 2023 Incoming to Southern Ontario (Wed, Apr 5, 2023)

A line of severe thunderstorms is possible across Southwestern Ontario on Wednesday and the risk will extend into isolated parts of Central, Niagara and the GTHA. The morning will bring heavy rain, hail and thunderstorms but the afternoon and evening will bring the strongest risk for damaging wind gusts (120km/h+), large hail (2-4cm), isolated flooding (50mm+) and frequent lightning. While the strongest risk remains stateside, the possibility of intense storms crossing continues to increase with each model run.

We’ve also identified an isolated tornado risk for much of Southwestern Ontario, stretching into parts of the GTHA and Niagara. There is a slightly more enhanced risk in deep southwestern Ontario closer to the US border and Lake Erie as well. However, we’ve seen models suggesting the risk could be a bit more widespread and further to the north. We may upgrade this risk but for now, we feel an isolated tornado region covers the chance of isolated tornado spin-ups tomorrow.

Be sure to stay informed and monitor weather updates as this potent storm system approaches. The impact of freezing rain, heavy rainfall, and possible severe thunderstorms, combined with significant ice accretion and potential power outages, could cause some disruptions to daily routines and travel plans.