Widespread Severe Thunderstorm Risk Across Southern & Northeastern Ontario on Wednesday
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As we welcome the first days of June across Southern Ontario, the warmer temperatures are a noticeable change from the end of May. Just last week, we were dealing with frost advisories in parts of the province. Now, temperatures are well into the 20s or even low 30s.
However, the bubbling heat will come at a cost with the return of thunderstorms, fueled by the hot temperatures. A line of storms, along with isolated cells ahead of it, is expected to extend from Northeastern Ontario southward into Southwestern Ontario sometime Wednesday afternoon or early evening.
Based on the predicted environment, these storms will have the potential to bring a ‘slight’ severe risk with damaging wind gusts up to 100 km/h as the primary threat. Hail up to the size of quarters and an isolated tornado threat can’t be ruled out.
There is some disagreement on exactly where this line will develop, which is associated with a cold front cutting across the region and bringing an end to the warmer temperatures. When this front arrives will be key to the overall storm threat. While storms could develop ahead of the line, the bulk of the severe threat will be concentrated with the squall line setup stretching from Lake Superior down into Michigan.
The latest data suggests that this line could form earlier in the day and start to cross over Lake Huron by the late afternoon or around the dinner hour. If it does end up arriving this early, the storms will be moving into a strong environment, allowing the squall line to potentially bring widespread damaging wind gusts as it tracks into Southwestern Ontario.
On the other hand, a later arrival in the evening would likely lead to the line of storms being weaker than expected and may only reach marginally severe levels. We do expect some gradual weakening in the line throughout the evening as it tracks into Central and Eastern Ontario by the mid to late evening hours. Non-severe thunderstorms could continue overnight and into early Thursday morning for Eastern Ontario.
As mentioned, we could see a few isolated cells pop up in Southwestern Ontario and maybe even around Lake Simcoe and Georgian Bay during the late afternoon ahead of the main line. If these storms can establish themselves, they could bring all severe hazards, including damaging wind gusts and up to toonie-sized hail. A tornado can’t be ruled out as these storms will have all the environment to themselves.
It should be noted that confidence in the isolated storms ahead of the line is questionable in Southern Ontario but could be more of a problem as we look at Northern Ontario.
For Northeastern Ontario, the confidence in isolated storms is much higher as we could see several cells develop along the Sudbury to Geraldton corridor during the afternoon and early evening. Similarly to Southern Ontario, these storms could bring damaging wind gusts and large hail, and the tornado risk is a little more elevated here due to a stronger environment.
This is also in addition to the squall line that will cross into the region from Lake Superior sometime around the dinner hour. At this point, the main threat will be damaging wind gusts up to 100 km/h, but we could still see some marginally severe hail and an isolated tornado. The squall line will gradually weaken as it tracks towards Quebec by the midnight hour.
There is a slight risk for severe storms stretching from Manitoulin Island through Elliot Lake and into Geraldton and Armstrong. This also includes the Lake Superior shoreline between Sault Ste. Marie and Marathon. The rest of Northeastern Ontario has a marginal severe risk.
For Northwestern Ontario, there could be a few pop-up storms during the afternoon and evening with a marginal risk around Thunder Bay. This risk will quickly diminish after sunset, which is providing the fuel to the pop-up cells.
