ONTARIO: Thunderstorm Forecast for Thursday, July 20, 2023
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FORECAST DISCUSSION
Get ready for what could be the most significant severe risk of the year (so far) in Southern Ontario on Thursday. The current data indicates a strong environment for severe weather, particularly in Southwestern Ontario during the afternoon and evening. As the day progresses, the severe potential will extend eastward into the GTA and Central Ontario, although the severity is expected to decrease the farther you are from Lake Huron.
However, there is a twist in the severe risk—storm development. While we have high confidence in the overall atmospheric conditions, it will rely on storms taking advantage of the energy. Currently, models show isolated storms initiating over Central Michigan in the afternoon and merging into a line of storms over Lake Huron by the early evening as they approach Southwestern Ontario. However, this timing may be too late for daylight heating to sustain these storms, causing them to weaken.
To heighten the severe threat on our side of the border, we need either an earlier arrival of the storm line (which is possible) or the development of isolated cells ahead of it. These storms could bring all severe hazards, including damaging wind gusts, significant hail, and the potential for one or two tornadoes. Otherwise, the later arrival would put more of a focus on damaging wind gusts with hail and tornadoes being lesser of a threat.
Although the overall environment could support a "significant" severe risk, we are currently maintaining a "strong" risk due to this uncertainty. If we gain more confidence in earlier storm development, we may upgrade the forecast. Stay tuned for further updates as we closely monitor the situation.
