Severe Thunderstorms Possible Across Southern Ontario Starting Late Sunday Into Monday Morning; Second Round of Storms for Eastern Ontario Monday Afternoon/Evening

Forecast Discussion

A very stormy day is ahead for Southern Ontario with multiple waves of potentially severe thunderstorms track across the province. The first wave will come late Sunday evening just before midnight as some decaying storms from Michigan reach Southwestern Ontario around the Windsor area. There are some indications that these storms could bring damaging wind gusts with localized gusts over 100km/h along with small hail and heavy rainfall. The tornado risk appears to be fairly low especially since it’ll be very late in the evening when they reach the area, but it can’t be completely ruled out since there is a tornado risk on the other side of the border. These storms will track to the northeast during the early overnight hours and could bring isolated damaging wind gusts as far east as the KW and Hamilton/Burlington region.

Another cluster of storms is expected to track over Lake Huron and move into parts of Northeastern Ontario just to the north of Georgian Bay early Monday morning. There could be the potential for strong wind gusts and moderate-sized hail associated with these storms as they affect the Manitoulin Island, Sudbury and North Bay area through the morning and even early in the afternoon.

The second and what could be the strongest round of the day will come later on Monday as a line of storms develops during the mid-afternoon somewhere in Central or Eastern Ontario. This line of storms will track eastward into the Ottawa Valley with the ingredients in place for very strong severe storms including damaging wind gusts, large hail, heavy rainfall and even one or two tornadoes. There is still some uncertainty on where this line will develop and how fast it’ll strengthen - it’s possible that the storms may not blow up until they cross into Quebec and Upstate New York which would decrease the threat on the Ontario side of the border.

This main threat for severe storms will be mainly during the late afternoon and early evening although it may linger later into the evening until the storms move out of the region. We’ll continue to monitor this and issue an updated outlook tomorrow morning or early afternoon based on how the morning storms progress.