Canada: Severe weather forecast across western regions through at least early Dec. 19 /update 1

Severe weather is forecast to continue over parts of western Canada through at least early Dec. 19. A Pacific frontal system will continue to bring heavy rainfall to southwestern coastal areas of British Columbia and snowfall to central and southern interior parts of the province Dec. 18. Heavy snowfall is also likely across parts of south-central and southeastern Alberta and southern Saskatchewan through early Dec. 19. Rainfall totals of 5-10 cm (2-4 inches) are possible in parts of southwestern British Columbia and snowfall accumulations of 10-30 cm (4-12 inches) are expected across parts of southern Alberta, central and southern British Columbia, and southern Saskatchewan. Extremely cold temperatures are forecast across parts of central and northern Alberta and south-central Saskatchewan; wind chill factors below -40 C (-40 F) are possible in these areas. Flooding is possible in areas where heavy rainfall occurs. Hazardous travel conditions are likely in areas where more wintry precipitation falls due to slippery roads and reduced visibility caused by blowing snow. Strong winds may cause property damage and power outages in parts of the affected area.

As of early Dec. 18, Environment Canada has issued red heavy rainfall warnings (the highest level on a three-tier scale) for parts of southern and western Vancouver Island and Metro Vancouver and surrounding areas. Red heavy snowfall warnings are in place for parts of south-central and southeastern Alberta, central and southern British Columbia, and southern Saskatchewan, as well as red snowfall and winter storm warnings for several highway passes across British Columbia. Red strong wind warnings have been issued for parts of the west coast and the far southeast of British Columbia. Grey special weather statements for freezing rain and heavy snowfall are in place for parts of southern British Columbia. Officials could 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 across much 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 will likely cause some delays and cancellations at airports in the region. 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.