US: Adverse winter weather forecast over northwestern and western regions through at least early Jan. 8

Adverse winter weather is forecast across parts of the northwestern and western US through at least early Jan. 8. Successive storm systems moving in from the Atlantic are expected to bring heavy snowfall over elevated parts of the region over the coming days, as well as rainfall in coastal areas. Snowfall accumulations of more than 20 cm (8 inches) are forecast across the Washington and Oregon Cascades. Heavy snowfall may combine with blustery winds to cause low visibility and hazardous driving conditions across parts of the affected area.

As of early Jan. 5, the National Weather Service (NWS) has issued winter storm warnings across parts of northern and eastern California and southwestern Oregon. Winter weather advisories have been issued across much of the rest of the affected area. Officials could update and possibly extend the coverage of weather alerts over the coming days.

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.

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.