Last Day of Summer on Wednesday to Feature Potentially Dangerous Thunderstorms Including Tornado Risk Across Southern Ontario
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It appears that the last day of ‘astronomical’ summer (meteorological summer ended at the start of the month) will go out with a bang for parts of Southern Ontario. This is courtesy of a strong cold front expected to sweep across the region on Wednesday and spark off potentially widespread severe thunderstorms starting early in the afternoon and continuing throughout the day. There is some uncertainty regarding the exact timing and intensity of the storms, but the environment is certainly favourable for a widespread damaging wind event along with the risk of tornadoes.
Current data suggest that the target zone for the strongest storms will be around the Georgian Bay shoreline in Central Ontario. However, not all models show storms developing to take advantage of the prime environment or developing too early in the day when daylight heating hasn’t built up enough. The most likely scenario appears to be a cluster of discrete storms developing over Lake Huron or Georgian Bay around the noon hour and tracking to the southeast throughout the early afternoon. This is when we believe the tornado risk will be at the highest as they come onshore around the Kincardine, Owen Sound, Collingwood, Barrie, Midland and Muskoka Lakes region between 12-2 PM (note: this timeframe is preliminary and may need to be changed). Large hail and damaging wind gusts are also possible from these storms.
As the storms continue to race across the region during the early afternoon, we expect to see the discrete cells slowly merge into a squall line with further development in Deep Southwestern Ontario. This means that the main threat will transition into a widespread damaging wind gust event as it tracks into the GTA and Niagara region by the mid to late afternoon. An isolated tornado still can’t be ruled out, but the risk is a lot stronger earlier in the day. It looks like Eastern Ontario will be spared from the worst of this severe threat, however, those in the far southeast including Belleville and Kingston could still be affected as the squall line tracks across Lake Ontario and into Upstate New York.
Keep in mind this is a very preliminary forecast as there is significant disagreement on storm development and exact timing which will determine the overall severity of these storms. It’s likely that we will have to make adjustments to the forecast based on the latest data from this evening and in the morning. While we’ve gone with a significant severe risk based on the environment, we may need to downgrade if it becomes apparent that storm development is more isolated or too early in the day. Be sure to check back on Wednesday for the very latest.
In addition to this, it will certainly feel like fall by the end of the week with colder air moving into Southern Ontario on Thursday and Friday. Some parts of our region will struggle to get above single digits as a daytime high on Thursday with a chill start on Friday morning as temperatures dip to near the freezing mark. We may even have to start talking about the risk of frost in higher elevations of Central and Eastern Ontario!
IMPORTANT: If storms start developing, we will likely be live-streaming via YouTube, Facebook, Twitter, and Twitch as we track every developing storm and notify those in the path of any rotation, tornado reports, damaging winds, and large hail on our free app Instant Weather and via our premium Text Message Alerts. If you don’t have PayPal, you can also subscribe to our text messages directly on our website, however, the PayPal option is automated so it will work immediately as we may not be able to get to everyone who subscribes via our website due to the fact that we have to enter those in manually.
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