ONTARIO: Thunderstorm Forecast for Wednesday, July 26, 2023
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FORECAST DISCUSSION
A striking sense of déjà vu sweeps over Southwestern Ontario as we face yet another significant severe threat on Wednesday. While this severe risk differs from last week's ‘extreme’ severe risk and will likely be a lot weaker, it could still pack a punch. The hail risk appears less prominent this time, with expected sizes ranging from toonie to ping pong balls, a departure from the baseball-sized hail we saw on Thursday. However, the tornado risk could be similar to last week with an isolated strong tornado risk. Widespread destructive wind gusts are also possible, and models suggest the potential for severe winds extending eastward into the GTA and Niagara region through the evening.
Our localized 'significant' risk target focuses on the Windsor, Leamington, and Chatham regions. An explosive environment combined with storms forming during the dinner hour heightens the danger. Yet, some model discrepancies in storm mode and timing add an air of uncertainty. If the storms appear earlier, they will have a stronger environment to work with while a later arrival would lessen the threat. It looks like a strong squall line of storms will develop over Michigan and track into Southwestern Ontario sometime between 6 - 10 PM.
It’s important to note that there are hints of a potential ‘bust’ with some models showing storms not developing at all or arriving way too late. This forecast is conditional on storm development. We can say the environment is capable to produce these storm threats but it requires a storm to realize these threats. We are hoping that storms don’t develop as this could get quite nasty if they do show up!
🔴 Significant Severe Risk for Deep Southwestern Ontario (Windsor, Leamington, Chatham):
115 km/h wind gusts
Hail up to the size of ping pong balls
Isolated strong tornado risk
Severe threat starts as early as 5 PM and grows by the hour before peaking around 7 - 10 PM. It should diminish by midnight.
🟠 Strong Severe Risk for the Rest of Southwestern Ontario (Sarnia, London, Lake Huron shoreline):
100 km/h wind gusts
Hail up to the size of toonies
One or two tornadoes
Severe threat starts as early as 5 PM and grows by the hour before peaking around 8 - 11 PM. It should diminish by midnight.
As with last week, the extent of storm progression into Ontario remains uncertain, contingent on timing. Nonetheless, the Kitchener-Waterloo, Greater Toronto and Hamilton Area, and Niagara region might face a severe threat later in the evening. At this point, the primary concern will be damaging wind gusts, with tornado and hail risks slightly diminished but not entirely out of the question.
Isolated storms are also possible this afternoon and evening across Central and Eastern Ontario. We have extended the isolated severe risk into this region to account for the pop-up storms possible later in the day.
Moreover, we have serious concerns over flash flooding potential. Model projections indicate some areas might encounter multiple rounds of thunderstorms within a 6-12 hour window, leading to localized rainfall totals exceeding 100mm, possibly even reaching 150-200mm. While not all areas will experience such deluge, urban centers prone to flooding could face significant issues if struck.
We continue to go over the data and will provide an updated forecast by early Wednesday afternoon in case of any last-minute data changes. Stay tuned! Remain weather-aware throughout tomorrow as we brace for potentially ‘grumpy’ conditions.
Intense storms over Central Manitoba are expected to move into Northwestern Ontario on Wednesday evening. These storms could be very severe with hail up to the size of golf balls, 100 km/h wind gusts and one or two tornadoes. The storm risk will diminish after midnight as these storms slowly weaken while tracking to the east. Isolated severe storms are also possible north of Georgian Bay around the Sudbury and North Bay region.
