Canada: Adverse weather forecast across southern Alberta, far southwestern British Columbia, and southern Saskatchewan through at least Dec. 7

Heavy rainfall, heavy snowfall, and strong winds are forecast across parts of southern Alberta, far southwestern British Columbia, and southern Saskatchewan through at least Dec. 7. Environment Canada has issued the following warnings:

• Red rainfall warnings (the highest level on a three-tier scale): Elk Valley near Fernie and Morrissey in British Columbia. Rain will continue late Dec. 6 before transitioning to snow early Dec. 7.

• Red freezing rain warnings: southern Saskatchewan. The freezing rain may be mixed with rain or snow and will taper off early Dec. 7 as the precipitation transitions to snow.

• Red snowfall warnings: Airdrie, Banff National Park, Canmore, Caroline, City of Calgary, Cochrane, Forestry Trunk Road Highway 734, Kananaskis, Nordegg, Olds, Rocky Mountain House, and Sundre in Alberta. Snowfall of 10-20 cm (4-8 inches) is forecast through Dec. 7. Precipitation will begin as rain or rain mixed with snow over lower elevations, before transitioning to snow.

• Red winter storm warnings: Crowsnest Pass, Pincher Creek, and Waterton Lakes National Park in Alberta. Heavy snow of 25-35 cm (10-14 inches) is forecast, with the highest snowfall totals likely over higher terrain.

Officials may update and extend the coverage of weather alerts over the coming hours.

The storm system could produce rounds of heavy precipitation (including rain and snow) and strong winds across the affected area. Where precipitation falls as rain, flash and areal flooding is possible. Such flooding is possible in low-lying communities near watercourses and other large bodies of water, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites located downstream of large reservoirs may be subject to flash flooding after relatively short periods of intense rainfall. Precipitation could fall as snow in northern parts of the affected area over the coming days. Wind gusts could cause blowing and drifting snow; decreased visibility is likely in these areas.

Floodwaters and related debris may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around the affected area. Flooding in urban areas could also result in significant traffic congestion. Heavy snow will likely make driving hazardous in some areas; authorities could implement temporary road closures or detours in such locations.

The disruptive weather could cause some delays and cancellations at airports in the region. Authorities may temporarily suspend port operations in coastal areas if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding or snow could block regional rail lines; freight and passenger train delays and cancellations are possible in areas that see heavy rainfall and potential track blockages.

Disruptions triggered by inclement weather and resultant hazards, such as flooding or strong winds, could persist well after conditions have improved - it could take days before any floodwaters recede and/or officials clear debris. If there is severe damage to infrastructure, repair or reconstruction efforts may result in residual disruptions.