ONTARIO: Thunderstorm Forecast for Friday, July 28, 2023
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FORECAST DISCUSSION
After a brief respite from the stormy skies on Thursday, we're closely monitoring the reemergence of severe thunderstorms for parts of Southwestern, Central and Eastern Ontario on Friday.
Central and Eastern Ontario, particularly the Ottawa Valley, will take the early spotlight as the afternoon and early evening present the perfect environment for isolated supercells. The exact location of storm initiation is unclear but could start as far west as Muskoka and Simcoe County by the early afternoon.
These storms will continue to track eastwards into Eastern Ontario where the environment is only expected to get stronger throughout the day. In light of this, we've gone with a 'significant' severe risk, encompassing Renfrew, Ottawa, and the eastern regions like Cornwall. Our main concern is the potential for an isolated strong tornado due to the potent atmospheric conditions. Additionally, large hail up to the size of golf balls and wind gusts surpassing 100 km/h are other possible threats.
Keep in mind that the risk in Central and Eastern Ontario will be very isolated. We anticipate only a few scattered storms, with most locations within our severe risk forecast likely remaining untouched. As always, the actual risk hinges on storm development taking advantage of the expected environmental factors.
Meanwhile, Southwestern Ontario remains a key area of focus, echoing the recurring pattern of strong severe thunderstorm risks over the past weeks. Models indicate the potential for yet another widespread damaging wind threat, originating from Michigan and crossing into our region. The timing, as always, holds the key to the actual risk on our side of the border.
Earlier in the evening, around dinner time, there are signs of a few isolated storms popping up over Lake Huron and southward into Sarnia and Windsor. These initial storms could present all severe hazards, ranging from hail up to ping pong ball-sized, 100 km/h wind gusts, and one or two tornadoes.
As the night progresses, a mature line of strong to severe storms is expected to impact Deep Southwestern Ontario between 10 PM to 1 AM. The strength of this squall line remains uncertain due to the event's timing, though it does appear more likely to pose a damaging wind gust threat, with localized pockets potentially reaching 110-115 km/h. Additionally, an isolated tornado can't be ruled out.
Further northward development ahead of the line could bring an isolated severe threat to areas around Kincardine and Lake Simcoe during the evening hours. As the line of storms tracks eastward along Lake Erie, it will impact the GTA with the potential for severe wind gusts lingering past midnight.
Localized flash flooding could also be an issue in both Eastern and Southwestern Ontario. This is because we expected rainfall totals could potentially exceed 100mm in localized areas that see multiple rounds of storms.
