Southern Ontario: Thunderstorm Outlook for Thursday, July 8, 2021

Forecast Discussion

A line of heavy rainfall will track across Southern Ontario starting during the late morning on Thursday and continuing right through to the early evening. This line will also feature some embedded thunderstorms that could be quite strong with wind gusts and very heavy rainfall rates. Although these storms should remain non-severe. The risk will come to an end later in the day as the area of rain moves out of the province.

Southern Ontario: Thunderstorm Outlook for Wednesday, July 7, 2021

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Forecast Discussion

An area of heavy rainfall with embedded non-severe thunderstorms is expected to track into parts of Southwestern Ontario and Central Ontario from Michigan overnight into Wednesday morning. Any thunderstorm will be quite weak, but widespread rainfall totals between 15-30mm and even up to 50mm for those that see thunderstorm activity is possible. So isolated flooding could be an issue especially since we’ve seen lots of rain over the past few weeks.

Later in the day, there could be some storms that develop through Extreme Southwestern Ontario. The environment is favourable for a few of these storms to reach severe levels with strong wind gusts and large hail possible. It doesn’t look like the tornado risk is particularly strong so we haven’t included it on the map, but keep in mind that it never is out of the question when we’re dealing with severe storms. Storms will weaken and move out of the region by midnight with potentially some non-severe thunderstorms and rain continuing overnight into Thursday.

Southern Ontario: Thunderstorm Outlook for Tuesday, July 6, 2021

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Forecast Discussion

A few pop-up non-severe thunderstorms are possible along the northern Lake Erie shoreline during the afternoon and early evening on Tuesday. These storms will be extremly isolated so not all locations will see them. Current indicaqtions suggest that any storms that develop will move quite slowly so flash flooding could be an issue with 50+mm of rain in a short timeframe. Other threats include moderate-sized hail and strong wind gusts, but they should remain non-severe aside from the flooding risk. The storm threat will come to an end late in the evening as the storms fizzle out after sunset.

Northern Ontario: Thunderstorm Outlook for Monday, July 5, 2021

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Forecast Discussion

There is a risk for severe thunderstorms throughout much of Northeastern Ontario during the afternoon and evening on Monday. The focus will be on regions just to the north of Georgian Bay where the strongest threat exists with even the potential for an isolated tornado.

Other parts of Northeastern Ontario along the Quebec border and northwards towards James Bay can expect a few isolated severe storms with strong wind gusts and moderate-sized hail as the main risk. The storm threat will come to an end late in the evening as the storms move out of the province and into Quebec.

Southern Ontario: Thunderstorm Outlook for Monday, July 5, 2021

Forecast Discussion

A very stormy start to the week is expected throughout Southern Ontario as hot, humid temperatures will lead to a fairly strong risk for thunderstorms with some of them reaching severe levels on Monday. The current target zone includes the shoreline around Georgian Bay and the northern parts of Lake Huron where we expect storms to develop sometime during the mid to late afternoon hours and track to the east or southeast.

This severe risk will also encompass the northern GTA and into parts of Central and Eastern Ontario with the main threat being damaging wind gusts over 100km/h as the line of mature storms sweeps across the region around the dinner hour. As for the tornado risk, it’s very questionable as the general storm mode favours more of a wind risk rather than tornadoes or large hail. Regardless, we’ve included a tornado risk on our map around Georgian Bay as there are some indications that a slight chance of a tornado or perhaps even a tornadic waterspout over Lake Huron or Georgian Bay that comes onshore is possible earlier in the lifespan of these storms.

The storm threat will continue late into the evening as the line of storms progresses into Eastern Ontario. It looks like the storms should weaken enough by midnight that they won’t pose a severe risk, but strong winds and heavy rainfall could continue to be an issue even into Extreme Eastern Ontario along the international border.

Northern Ontario: Thunderstorm Outlook for Monday, July 5, 2021

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Forecast Discussion

Thunderstorms are possible during the afternoon and evening on Monday throughout Northeastern Ontario. These storms should be mainly non-severe although one or two near-severe storms can’t be ruled out. However, the confidence in this event is low at this time.