US, Canada: Adverse winter weather forecast across western parts of Canada and the US through at least Dec. 2

Event

Waves of moisture from the Pacific Ocean and a low pressure system are forecast to bring snowfall, rain, and strong winds to parts of southwestern Canada and northwestern and western parts of the US through at least Dec. 2. Coastal rain and mountain snow are expected in the region early Nov. 29 before the system strengthens and brings more widespread snowfall to lower elevations through Nov. 29 and into Nov. 30. The storm is expected to push southwards into northern California from Nov. 30, bringing snowfall to higher elevations and rainfall to coastal areas. Cold Arctic air and strong winds are expected across parts of western and southwestern British Columbia over the coming days. Snowfall accumulations of more than 10 cm (4 inches) are possible at higher elevations in Washington and Oregon Nov. 29 and accumulations of more than 20 cm (8 inches) are likely Nov. 30-Dec. 1. Accumulations of more than 20 cm (8 inches) are also likely over the ranges of central Idaho, far western Montana, and northern California Dec. 1. Snowfall accumulations of 10-30 cm (8-12 inches) are forecast across parts of southwestern British Columbia in the coming days, as well as winds gusting up to 90 kph (56 mph). Heavy snow accompanied by strong winds will likely lead to hazardous driving conditions due to slippery roads and reduced visibility.

Government Advisories
As of early Nov. 29, the National Weather Service (NWS) has issued winter storm watches for much of Washington and parts of eastern and far western Oregon, northern and eastern California, northern and central Idaho, and western and southwestern Montana. Winter weather advisories have been issued over parts of north-central Idaho and western Montana. Freeze watches and warnings are in place over parts of central Califonia and high wind warnings have been issued for coastal areas of eastern Oregon and southeastern Washington.

Environment Canada has issued snowfall, wind, and Arctic outflow warnings over parts of southwestern and western British Columbia, as well as special weather statements advising of snowfall, strong winds, rainfall, and dropping temperatures. Officials could update and possibly extend the coverage of weather alerts over the coming days.

Hazardous Conditions
Snow accumulations are likely across the affected area, especially at higher elevations. Lesser accumulations are possible where sleet and freezing rain mix with the snow and precipitation is less intense. In addition to the heavy snow, strong wind gusts will likely lead to periods of blowing and drifting snow in some areas. Blizzard conditions are possible. Sporadic power outages could occur throughout the affected area.

Transport
The winter weather will likely cause ground and air transport disruptions over the coming days. Traffic and commercial trucking delays are possible along regional highways. Dangerous and challenging driving conditions are also likely on secondary and rural roads in the affected states as maintenance crews prioritize clearing major routes. Authorities could close stretches of highways if driving conditions become too hazardous. Flight delays and cancellations are likely due to ground stops and deicing operations at regional airports.

Advice

Monitor local media for updated weather information. Verify road conditions before driving in areas where heavy snowfall is forecast. Allow extra time to reach destinations in these areas and carry an emergency kit and warm clothes if driving is necessary, especially on secondary or rural routes that could become impassable. If routing shipments by truck through the affected area, plan accordingly for delivery delays. Confirm flights. Charge battery-powered devices in the case of prolonged electricity outages.

Resources

National Weather Service
Weather Prediction Center
Environment Canada