FORECAST UPDATE: Widespread Severe Thunderstorm Risk for Monday Across Southern and Northeastern Ontario

NOTE: You can click on the map to open a zoomable image which will be easier to read.


As we mentioned in our preliminary forecast yesterday, there is a risk of severe thunderstorms across Southern Ontario for Monday afternoon and continuing into the evening/overnight hours. While the focus yesterday appeared to be the Lake Simcoe region and the Lake Huron shoreline, we have now expanded the severe risk into the Ottawa Valley. Current data indicates that storms may pop up further to the northeast than expected and combined with a very robust environment, they could become quite severe with all severe threats including tornadoes possible.

Heading into the afternoon, we will be watching two zones for the development of isolated storms through Central and Northeastern Ontario. Storms are expected to pop up around the Collingwood/Barrie area early this afternoon and track to the northeast through northern Kawartha Lakes, Bancroft and Renfrew/Pembroke. These storms have the potential to bring damaging wind gusts, large hail and an isolated tornado. Some models are hinting towards some storm development over Lake Ontario which could affect Prince Edward County and Kingston, but the potential isn’t high enough to warrant upgrading them to the next severe level.

NOTE: You can click on the map to open a zoomable image which will be easier to read.

Similarly, we also expect to see some development in the north around the Wawa and Kapuskasing area this afternoon and slowly track to the east towards the Quebec border. Locations like Timmins, Cochrane and Chapleau have the highest chance of a tornado, but the risk of a tornado can’t be ruled out throughout Northeastern Ontario including Sudbury, Elliot Lake and North Bay.

The squall line that was expected to affect the Lake Huron shoreline will still present a risk but is now expected to develop over Michigan and not reach our region until late evening. As a result, the main threat with this line will be very strong wind gusts (90-100km/h) stretching from Tobermory and all the way into the Windsor area. We have kept the tornado risk along the Lake Huron shoreline and into Deep Southwestern Ontario, but the environment won’t be as strong after sunset so it’s questionable at best. If we do see a tornado, it would likely be right along the shoreline as the storms make landfall late in the evening. It will continue to track to the east throughout the overnight hour, but the severe risk will diminish as the line slowly weakens after midnight.


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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