Rainfall warnings west of Calgary, and severe thunderstorms likely

As expected a slow-moving low pressure system moving in to Alberta from southern B.C. has prompted Environment and Climate Change Canada (ECCC) to expand rainfall warnings first issued on Wednesday.

Areas along the foothills – including Kananaskis and Canmore, are now included under this advisory.

“Heavy rain will begin today, with total amounts of 50 to 80 milimetres (expected)," ECCC said.

The weather agency also notes “areas in the foothills will see heavy rain and embedded thunderstorms begin by Thursday afternoon and intensify through the evening hours.”

Strong winds will precede this system, and convective activity is expected to last for a good portion of the day in affected areas, including Calgary.

Daytime heating is often a key element aiding in the development of severe thunderstorm, and if there is a window for surface heating to occur today that will enhance storm energy.

But mechanical lift can also serve to assist in storm development – and that is the more likely scenario for Thursday in southern Alberta.

As of 7 a.m. Thursday, the only advisories that had been issued from ECCC were rainfall warnings – but it would be reasonable to expect to see severe thunderstorm watches or warnings as the day continues.

This low is going to remain slow-moving on the Alberta side of the Rockies, so areas that are caught under it will likely have significant rainfall totals including Calgary, with around 30 milimetres expected.

Sunshine will make a brief return Friday afternoon and Saturday. Rain is likely on Sunday and Monday for Canada Day celebrations.