This weekend won't be particularly ideal for outdoor activities for many parts of the Prairies, with extreme heat, humidity and the ongoing risk for thunderstorms, which could become severe some areas on both days. Saturday includes a very conditional tornado threat in parts of Alberta and Saskatchewan. The latter takes the brunt of the heat Saturday, with daytime highs into low-30s, then pushing into southern Manitoba for Sunday with similar temperatures and humidex values in the 40s. More on the weekend storm threat and just how hot it’ll get, below.
THIS WEEKEND: MULTI-DAY THUNDERSTORM THREAT AMID EXTREME HEAT
Saturday and Sunday will be hot, and possibly stormy, on the Prairies thanks to the heat and humidity, as well as other ingredients in place.
Severe thunderstorms will be possible in southern Alberta and Saskatchewan on Saturday as a low-pressure system advances north from Montana into southern Saskatchewan. Severe thunderstorm watches are in place in southern Alberta.
Isolated to scattered thunderstorms will continue to develop Saturday morning in Alberta with the help of southerly winds ahead of a trough originating from B.C.
There will be a risk of stronger storms by the late afternoon and evening as a low tracks over southwestern Saskatchewan and moves northeast.
With very high CAPE values and shear present within the atmosphere, dynamics are favourable for supercells Saturday in extreme southern Alberta that could track northeast into Saskatchewan, carrying the risk of a tornado into the late-evening hours, along with large hail. The tornado threat is very conditional.
By Sunday, the severe storm potential lingers in southeastern Alberta while pushing farther east into southern Saskatchewan, southern Manitoba and northwestern Ontario as the low-pressure system continues to track in that direction. The possible hazards with severe storms include strong wind gusts, large hail and heavy rain.
However, such extreme heat means there will likely be a cap in place, but storms that are able to break through it will likely turn severe very quickly.
WIDESPREAD HEAT WARNINGS IN EFFECT
In addition to the multi-day thunderstorm threat, days of high heat and tropical humidity will spread from west to east across the southern Prairies this weekend. Daily temperature records and dangerous humidex values are likely.
Heat warnings are in effect across Saskatchewan and southern Manitoba, along with special weather statements, as a heat dome in the southern U.S. will nose the northern part of the ridge into the Prairies.
Widespread low- and close to mid 30-degree temperatures are forecast for southern Saskatchewan on Saturday while southern Manitoba will be the focus for the mid-30°C heat on Sunday.
Humidex values will be into the 40s for parts of the aforementioned regions Saturday and Sunday, respectively.
"Extreme heat affects everyone," says Environment and Climate Change Canada (ECCC) in the heat warning.
"The risks are greater for young children, pregnant women, older adults, people with chronic illnesses and people working or exercising outdoors. Watch for the effects of heat illness: swelling, rash, cramps, fainting, heat exhaustion, heat stroke and the worsening of some health conditions. Drink plenty of water even before you feel thirsty and stay in a cool place. Check on older family, friends and neighbours. Make sure they are cool and drinking water."
Much cooler conditions are expected next week, though remaining warmer at times for parts of Manitoba.
Thumbnail courtesy of Marjorie, taken in Kleefeld, Man.
Be sure to check back for updates this weekend as we continue to fine tune the forecast details on the storm timing and severity.