Thunderstorm leads to heavy flooding, traffic delays in parts of Calgary

A thunderstorm caused heavy flooding in many parts of Calgary on Thursday, leading to multiple road closures and many commuters being stranded on the streets.

The city's northwest was especially hard hit and many residential neighbourhoods were impacted, such as Tuscany, Valley Ridge and Bowness. 

Commuters experienced severe traffic in several areas, including Stoney Trail, Nose Hill Drive, eastbound John Laurie Boulevard and 14th Street N.W. 

"Last night, a thunderstorm formed sort of northwest of the city and slowly drifted over the northwestern corner of the city, dropping quite a bit of rain and a little bit of small hail," said Environment Canada meteorologist Sara Hoffman.

She noted a thunderstorm warning was issued at 5:45 p.m. and it ended at 7:19 p.m., making it a relatively "long-lasting thunderstorm over the area." 

According to the meteorologist, the severity of rainfall was drastically different in some parts of the city with certain areas receiving 20 millimetres of rain while others dealt with as much as 90 millimetres.

Flash floods caused major traffic congestion in some areas, leaving many Calgarians stranded for several hours.

This is not an unexpected outcome, according to Hoffman, who said 20 to 50 mm of rainfall in an hour is enough to cause flooding.

'It was kind of like a test'

According to Hoffman, there's another thing worth considering when it comes to flash floods: hail.

"When you get quite a bit of small hail all at once, followed by a lot of rain, that hail can actually act to kind of clog drainage that would normally take away that rain," she said.

Michael Gretton, who was stuck in traffic for over three hours after running errands in Valley Ridge, was surprised by the gridlock on the roads.

"[I've] never experienced this in Calgary ever. I felt like I was in Toronto or something," he said. 

"For me, it was kind of like a test just to stay calm and not to get too concerned about things [and] just let it ride out."

According to Acting Staff Sgt. Colin Foster of the Calgary Police Service, it's a good idea to check the weather forecast in such situations to ensure it's safe to step out.

He advises the public to avoid heading out in severe weather unless necessary. In case someone gets stranded, Foster recommends heading to safe locations like the underside of bridge decks and garage forecourts.

He added it's best to not stop on the side of a road when you're dealing with extreme weather.

"The actual shoulder on any roadway is one of the most dangerous places you can stop," he said. "A vehicle that may decide to continue driving in these conditions, if they lose control, there's that potential that they're going to come across and strike your vehicle."

Brace yourself — the weather forecast indicates there may be another thunderstorm tonight. 

"We definitely have thunderstorms in the forecast for today, Saturday and Sunday," Hoffman said. 

"We don't anticipate thunderstorms to be severe any of these days, but today the storms definitely have a little bit more energy than Saturday and Sunday."

Learning experience

For Gretton, being stranded on the streets was a learning experience in more ways than one.

He was impressed by how respectful other drivers were even though it was a gridlock with long wait times.

He took away a few major lessons from the incident — always have a tank full of gas, be considerate and … visit the bathroom before heading out.

"You never know how long you're going to be," Gretton said. "I think just, you know, be patient, be kind. You know, these things are beyond our control."