Tornado warning for central Alberta as supercell activity triggers ...

A tornado warning was issued just after 7 p.m. for a swath of central Alberta, where a line of severe thunderstorms could possibly be producing a tornado. The warning was later dropped around 9 p.m.

Visit Alberta Emergency Alert for the latest details.

After days of high temperatures, a drop in the mercury has also coincided with a low-pressure event that is bringing what Environment Canada calls a “smorgasbord of high-impact weather through to the end of the week, potentially ending the ongoing heat wave with a bang.”

The national weather agency issued watches for tornadoes and severe thunderstorms on Wednesday afternoon across much of central and southern Alberta.

(For a full list of areas affected, visit this Environment Canada website as it will change throughout the day as systems move.)

“After about eight days of heat warnings across Alberta, we now head into different warnings,” said Global Edmonton weather specialist Ciara Yaschuk.

Tornado watches are issued when atmospheric conditions are favourable for the development of thunderstorms that could produce tornadoes.

Strong winds, large hail and heavy rain are also possible in parts of Alberta, Environment Canada said.

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Environment Canada’s daily significant weather discussion said the overall environment looks primed for supercells, with all severe hazards possible, including tornadoes and very large hail.

“A severe thunderstorm watch is currently blanketing the Edmonton area all the way past Calgary, including a tornado watch for all communities between Wetaskiwin and Calgary. Strong winds, large hail and heavy rain are also possible,” Yaschuk said Wednesday afternoon.

Thunderstorms form when moist, warm air rises. The air expands and cools, forming a cloud. Atmospheric instability, such as strong wind shear (the change in wind speed and direction) is essential in the formation of thunderstorms.

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Supercells are the king of all thunderstorms; in Alberta, they typically begin to develop in the foothills throughout the day, building energy before sweeping east across the Prairies in the afternoon and evening.

A supercell is a large, single-cell, severe storm. Supercells are capable of producing tornadoes, hail and damaging winds. It possesses a strong, rotating updraft, or air that is moving up within the developing system.

The updraft, called a mesocyclone, can reach speeds higher than 160 km/h. The rotation of a supercell can often be spotted from the ground.

Environment Canada said while the conditions exist for tornado and severe thunderstorm activity, especially in the QEII corridor between Red Deer and Calgary, wildfire smoke will play a significant role in how the weather develops through the afternoon and evening.

“Should fires over the Rocky Mountains become active this afternoon, large plumes of smoke may enhance the cap and inhibit convection until much later in the day,” the weather summary said.

“Should this be the case, the tornado risk may remain muted although long-track severe thunderstorms will likely continue well into the night as the parent low tracks northeast toward Lake Athabasca by Thursday.”

If that is the case, any late-night convection is highly likely to evolve into more of a wind threat, the agency said.

“The only positive here — Jasper could see five to 10 mm of rain (Wednesday night), which would hopefully help with some of the active fires, including air quality,” Yaschuk said.

To receive the latest severe weather alerts for their region people are highly encouraged to download the government’s Alberta Emergency Alert app.

To get real-time weather for your area, download the Skytracker weather app.

— with files from Nicole Mortillaro, Global News