WEYBURN — Residents across southeastern Saskatchewan and southern Manitoba are bracing for what forecasters are calling an extreme risk of severe weather Tuesday, with the potential for strong tornadoes, giant hail and widespread destructive winds.
Update: At 4:25 p.m., Environment Canada says meteorologists are tracking a severe thunderstorm capable of producing damaging winds and heavy rains in the RM of Moosomin, including Moosomin, Welwyn and Fleming.
Environment Canada's official forecast outlook warns of a significant severe weather outbreak from this afternoon through tonight. Primary hazards include very large hail, tornadoes that could potentially be strong and widespread damaging wind gusts exceeding 100 km/h. Meteorologists note the conditions are ripe for a derecho, a massive and long-lived straight-line windstorm, alongside torrential rainfall of 50 to 100 millimetres that is highly likely to trigger flash flooding.
The atmosphere across cities such as Weyburn, Estevan and Regina is currently acting like a pressure cooker. A layer of warm air higher in the atmosphere, known as a cap, is holding back the explosive energy building from surface temperatures in the upper 20s and unusually high humidity. While the early afternoon may seem deceptively calm and hazy, forecast models indicate that the atmospheric lid will break rapidly. Yorkton-based storm chaser Ryan Crouse expects the action to begin in the mid-afternoon.
“Storms can actually happen, I would say anything after 3 p.m.,” he said.
Once the cap breaks, explosive supercell thunderstorms are expected to develop rapidly. In the Estevan and Regina areas, the severe weather window opens around 3 p.m. to 4 p.m., bringing an initial high risk of isolated, rotating storms capable of producing tornadoes. Weyburn and Yorkton will likely see this violent eruption closer to the evening commute. For the Yorkton region specifically, Crouse noted the window for severe development is likely between 4 p.m. and 7 p.m.
Crouse said the setup for today is highly unusual for the start of the summer severe weather season, describing the massive scale of the system as an anomaly for this early in the year.
“For the fact that it was literally the start of the storm season, it's actually, for all the years I've been chasing, I would almost consider it very unusual,” he said, noting it is more typical of late-July weather. “So, it's like the southern storms in the States have pushed north, giving us like the American-style storms.”
The threat is expected to unfold in two distinct stages. First, isolated supercells will form in the warm, humid sector ahead of the main system, bringing the highest risk for tornadoes. As the evening progresses, these isolated storms are expected to merge into a massive squall line that will sweep east toward Manitoba. This transition brings a significant danger from torrential rain and damaging gusts.
“The bad thing with that is usually when it becomes a squall line is when it backfills,” Crouse warned. “And when it backfills, you get all the heavy, heavy, heavy wind and heavy rain, much like we had Sunday.”
This heavy, backfilling rainfall is a major concern for communities still recovering from the weekend's intense weather. With an additional 50 to 100 millimetres of new rain forecast for today, the already saturated ground could easily lead to rapid street flooding, particularly under overpasses and in low-lying neighbourhoods.
“I hope everyone who's dealing with these flood situations doesn't get hit again today, because we definitely don't need it,” Crouse said. “I've got friends and family in the Swan River and Minitonas area, and even places like Roxton and Calder that got six and a half inches of rain Sunday night.”
Residents in the path of these storms are urged to remain highly vigilant today. As the intense severe weather window opens late this afternoon, Environment Canada is expected to issue a rapid succession of watches and warnings. Forecasters advise having a reliable way to receive weather alerts and seeking shelter immediately when warnings are issued in your area, as the worst of the explosive energy is expected to impact the region through the dinner hour before tracking east into the night.
