US: Adverse weather forecast to continue across northwestern regions through at least Jan. 18

Severe weather is forecast to continue across parts of the northwestern US through at least Jan. 18. A storm is forecast to track over the Pacific Northwest Jan. 17-18, bringing rain over parts of the Pacific Northwest into northern and central California, with snow over higher elevations. Heavy snow is likely over the Northern Cascades, while heavy rain and freezing rain are likely over the Columbia River Basin from the evening of Jan. 17 to the evening of Jan. 18. Snow and ice may result in hazardous road conditions across the affected area.

As of late Jan. 15, the US National Weather Service has issued ice storm warnings across northwestern Oregon and far southwestern Washington and winter storm warnings across northern Idaho, northwestern Montana, far northeastern Oregon, and western and eastern Washington. Winter weather advisories have been issued for most of the rest of the affected area. Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

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.

Where precipitation falls as snow, strong wind gusts could lead to periods of blowing and drifting snow; decreased visibility is likely in mountainous areas. Sporadic power outages are likely throughout the affected area.

Floodwaters and snowfall accumulations will likely 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. Mountain passes and tunnels could be closed as a precautionary measure during periods of intense snowfall.

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.