MANITOBA: Thunderstorm Forecast for Tuesday, August 1, 2023

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Prepare for an eventful day on Tuesday as two rounds of thunderstorm activity are set to impact Southern Manitoba. Here's what you need to know:

🌩️ First Round: Early Morning Severe Thunderstorms

A line of robust and severe thunderstorms are expected to form in the Interlake region early Tuesday morning. These storms will pack a punch as they track southeastward towards the Ontario border, reaching the vicinity of Winnipeg during the mid to late morning. However, the severity of the risk for Winnipeg remains uncertain at this point.

The potential threats associated with this initial line of storms will include hail, possibly reaching the size of quarters, along with strong wind gusts of up to 100 km/h. Additionally, heavy rainfall is expected to accompany these storms.

🌩️ Second Round: Isolated Strong Storms

Later in the day, somewhere between the late afternoon and early evening, we may witness the development of isolated storms in South-central Manitoba, particularly along the US border. While these storms will be highly localized, they have the potential to be quite intense.

With hail possibly as large as ping pong balls, 100 km/h wind gusts, and localized flash flooding, these isolated storms are expected to bring a severe impact to the affected areas. An isolated tornado can’t be ruled out either.

Decoding Thunderstorm Forecasts: Threats Over Probability ⚡️🌩️

When it comes to thunderstorm forecasts, there are two distinct approaches:

  • Forecasting the probability of thunderstorms occurring based on storm development.

  • Forecasting the potential thunderstorm threats based on the environment.

Both methods have their merits, but at Instant Weather, we prioritize focusing on the threats rather than just the probability. After all, it's the possible threats that pose a real danger to you.

We achieve this by carefully evaluating the latest model data and assessing the level of threat posed by each type should storms develop in a particular region. This includes the risk of tornadoes, damaging winds, large hail, and flooding.

Our overall severe risk classification comprises 6 categories: non-severe, isolated, slight, strong, significant, and extreme. The final category is determined based on the maximum threat level among all the individual threat types.

The graphic above highlights the risk levels of each threat type and their correlation with the overall severe risk. Minor regional differences exist between Ontario and the Prairies; for example, tennis ball-sized hail is classified as a 'strong' risk in the Prairies, while in Ontario, it's considered 'significant'. This variation results from the higher frequency of large hail occurrences in the Prairies compared to Ontario.

Please note that our forecast map doesn’t focus on probabilities, so we don't guarantee storms for a specific region.

In fact, most locations within a region may not experience a single storm. The localized nature of storm development makes it challenging to predict. Instead, we aim to inform you about the potential threats IF storms develop in a given area, based on the surrounding environment.

For a comprehensive understanding of how widespread an event could be and the potential for a ‘bust’, we encourage you to read the entire forecast discussion.