As southeast Saskatchewan deals with an early July heatwave, meteorologists are watching the skies with cautious anticipation. With temperatures expected to reach the low 30s and humidex values pushing 40, the atmosphere over southeast Saskatchewan is primed for potential severe thunderstorms, but whether those storms actually form remains the big question.
“It’s kind of one of those days that’s a bit of a quandary to meteorologists,” said Brian Proctor, meteorologist with Environment and Climate Change Canada. “We have potential instability in the atmosphere, and a bit of a trigger coming in, but at the same point in time, the atmosphere is largely capped.”
The “cap,” or capping inversion, acts like a lid on a pot. While the sun heats the surface and builds energy underneath, a layer of warm air aloft prevents that energy from rising freely. Unless surface temperatures climb high enough or a weather system provides sufficient lift to "pop the lid," thunderstorms struggle to develop.
Thursday’s atmospheric soundings show just how close the southeast is to that tipping point. The afternoon RAP, or Rapid Refresh, model showed convective available potential energy, or CAPE, near 1550 J/kg, more than enough to fuel strong thunderstorms, while the convective inhibition is expected to drop below 90 J/kg around 6 p.m. That’s a significant weakening of the cap compared to the early afternoon, suggesting storms could develop if a trigger arrives.
“If it hits, it’s probably going to happen to have fairly big storms,” Proctor says. “But if it misses, it’ll be because it’s capped, more than anything else, in the atmosphere.”
Meteorologists are estimating a 30 to 40 per cent chance of thunderstorm development late this afternoon into the early evening in the southeast. If storms do form, they could become severe, with large hail, damaging wind gusts, and localized downpours. Tornado potential remains low, but not entirely off the table, particularly near the Manitoba border.
Adding to the local anxiety is the fact that early July tends to be packed full of local events.
Proctor chuckled about how it seems like major events like fairs always have a day or two of a storm moving through.
“Whenever the Calgary Stampede happens, we’re bound to get one or two really good hail events during the Calgary Stampede; it seems inevitable,” Proctor laughed. “Oftentimes we seem to sort of see that analogy that we get these summer fairs or summer events happening, and we get more severe weather, but it’s largely because we do these events in July and August, which tend to be the most active severe weather seasons.”
A modest cooldown is expected over the next few days, with highs dipping to the upper 20s Friday and Saturday and potentially as low as 20°C by Sunday. But it won’t last long.
“We start seeing those temperatures climbing back up into the high 20s, low 30s by Tuesday, and up to the mid-30s by Wednesday,” Proctor added.
You can stay up to date with the latest weather information on the Discover Estevan Weather page.