US: Adverse weather forecast across western regions through at least early Feb. 2

Severe weather is forecast across parts of the western US through at least early Feb. 2. A storm system generated by an atmospheric river funneling moisture in from the Pacific Ocean will bring heavy rainfall to coastal areas of southeastern Oregon and northern and central California Jan. 31-Feb. 1. The heavy rainfall will likely shift southward into southern California Feb. 1-early Feb. 2. Strong winds are also expected across much of the affected area and snowfall is likely in mountainous parts of the region. Heavy downpours may trigger flooding in low-lying areas and strong winds may cause property damage and power outages. Hazardous travel conditions are likely in mountainous areas due to reduced visibility caused by blowing snow.

As of Jan. 30, the US National Weather Service (NWS) has issued flood watches across parts of north-central California and winter storm watches over parts of eastern and northern California and central Nevada. High wind warnings and wind advisories are in place across much of southern Oregon and central and northern California. Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

The NWS's Weather Prediction Center has forecast a slight risk of excessive rainfall over coastal areas of northern and central California and some inland areas of north-central California Jan. 31-Feb. 1. There is a further slight risk of excessive rainfall for coastal areas of southern California Feb. 1-2.

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 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.