Canada: Adverse weather forecast across western regions through at least Oct. 21

Severe weather is forecast across parts of western Canada through at least Oct. 21. A developing atmospheric river is expected to bring heavy rainfall across southwestern and southeastern areas of British Columbia, with strong winds also likely along western and southwestern coastal areas. Rainfall totals of 4-10 cm (1.6-2 inches) are expected across parts of the region, with localized higher amounts up to 20 cm (4 inches). Further to the north, the first significant snowfall of the season is likely in parts of northern British Columbia and southern Yukon. Snowfall accumulations of 5-25 cm (2-10 inches) are forecast in affected areas. Flooding is possible in areas where heavy rainfall occurs and hazardous travel conditions are likely in areas where more wintry precipitation falls due to slippery roads and reduced visibility caused by blowing snow.

As of Oct. 17, Environment Canada has issued red snowfall warnings (the highest level on a three-tier scale) for Cassiar Mountains and Watson Lake in British Columbia and Yukon. Red strong wind warnings are in place for some western coastal areas of British Columbia. Grey special weather statements have been issued for snowfall in other parts of northern British Columbia and southern Yukon, as well as for heavy rainfall and strong winds in parts of southwestern British Columbia and heavy rainfall in parts of southeastern British Columbia. Officials may update and extend the coverage of weather alerts over the coming hours.

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 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 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 or snowfall due to potential track blockages.

Disruptions triggered by inclement weather and resultant hazards, such as flooding or snowfall accumulations, 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.