Intense rain continues; risk of water pooling, falling trees, high streamflow, eroding stream banks

As expected, a slow-moving system is producing intense amounts of rain over Alberta, prompting warnings across most of the province.

A yellow-level rainfall warning was issued by Environment and Climate Change Canada (ECCC) along the eastern half of the province, extending from just south of the northeastern border down to the southern international border, and then west of the QEII and Highway 2 corridors.

The national weather agency explained, “Heavy rain continues, with total amounts of 50 to 100 mm expected. Localized total amounts in excess of 100 mm are possible.”

Water is expected to pool on roadways and in areas at the base of hills as the ground becomes too saturated to absorb any more moisture.

Waterways including the Bow and Elbow Rivers have reported increased volumes and high streamflow rates, and there is concern around bank erosion.

These situations all require caution, as detailed by ECCC, “Don’t drive through flooded roadways. Watch for washouts near rivers, creeks and culverts.”

To the west of this rainfall warning is a weather statement that includes the cause of additional strain to local waterways.

“Rain continues. Total amounts of 40 to 60 mm are expected by the time rain tapers off Tuesday evening. Snow will fall over higher elevations. Total amounts of 10 to 20 cm are possible, with the highest snow accumulations expected above 2,000 m,” ECCC said.

East of Calgary, there is a yellow-level wind warning.

“Strong winds gusting up to 80 km/h will continue through this evening. Saturated soil from heavy rain increases the risk of falling trees. Local utility outages are possible. Some property damage is possible,” ECCC said.

Calgary is expecting at least an additional 25 to 35 millimetres of rain on Monday with more rain Tuesday.

The wind will also be intense in the city, with sustained speeds of 40 to 70 km/h on Monday.

The greatest risks for Calgary are associated with saturated ground and water pooling on paths and roadways, downed trees and power lines and rain damage to property and structures.

A blocking pattern in the upper levels known as an Omega Block is the main cause of this persistent rain and instability.

Hot, dry, and stable conditions remain over central Saskatchewan and Manitoba, where a high-pressure system remains anchored by two low-pressure systems to the southeast and southwest.

That southwestern low sitting just south of the Alberta-Saskatchewan border is expected to funnel moisture east to west against the Rockies until the middle of the week.

Daytime highs will remain well below seasonal until the middle of the week, with Calgary expecting maximum temperatures of 8 C to 9 C on Monday with lows of 7 C.

The normal range this time of year is 18 C and 6 C.