ONTARIO: Thunderstorm Forecast for Thursday, June 15, 2023

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FORECAST DISCUSSION

There is the potential for strong thunderstorms over Deep Southwestern Ontario this Thursday afternoon and evening, particularly impacting areas such as Windsor, Leamington, and Chatham.

The current data indicate that a series of discrete storms, potentially developing into supercells, are likely to form in Southeastern Michigan near Detroit, moving towards Southwestern Ontario around dinner time. With the strong environmental conditions, these storms pose significant threats, including hail up to the size of golf balls and wind gusts reaching 100 km/h. A tornado threat is also associated with these storms, as detailed further below.

This severe weather threat will predominantly be localized to Deep Southwestern Ontario, with a slight risk extending from Sarnia to St. Thomas. An isolated severe storm might also occur as far north as Grand Bend, Woodstock, and Brantford. Meanwhile, non-severe but sporadic thunderstorms could affect other parts of Southern Ontario, but not everyone will witness these storms.

TORNADO RISK

Tornado potential, particularly in the Windsor, Leamington, and Chatham regions, is another concern we're closely monitoring. These areas, with the strongest environmental conditions, could see one or two tornadoes primarily during the late afternoon and early evening hours. An isolated tornado risk also includes the rest of Deep Southwestern Ontario, encompassing areas like Sarnia and London.

In more northern regions, like the Golden Horseshoe and Eastern Ontario, there are some signs that the environment could support funnel cloud development. These funnel clouds typically don't touch the ground but there's a slim chance they could touch down and become landspout tornadoes. However, this largely depends on whether storms will even materialize in these regions to exploit the given environmental conditions.

Landspout: A landspout is a type of tornado that forms under a weak thunderstorm. Unlike traditional tornadoes, which develop from supercell thunderstorms and are associated with a rotating updraft called a mesocyclone, landspouts form from non-supercell storms and do not have a mesocyclone. These tornadoes are generally weaker and shorter-lived than their supercell counterparts but can still pose a threat to property and life, with wind speeds occasionally reaching up to 160 km/h.