Japan: Adverse winter weather forecast across most of the country through at least March 21

Adverse winter weather conditions are forecast across most of Japan through at least March 21. Heavy snowfall and strong winds are forecast in many areas and may cause blizzard conditions.

As of early March 20, the Japan Meteorological Agency (JMA) has warned of strong winds and high waves in western Japan March 20 and from eastern to northern Japan March 21. Lightning strikes, severe gusts of wind such as tornadoes, heavy rain, and hail are forecast from western to eastern Japan. Traffic disruptions are possible due to heavy snow along the mountains. The following weather warnings are in place:

• Red snowstorm warnings (the middle level on a three-tier scale): Eastern Iwate and eastern Tottori prefectures

• Red storm warnings: Aichi, western Ehime, northern and eastern Fukuoka, Fukui, eastern Fukushima, Ishikawa, eastern Miyagi, most of Oita, western Yamagata, and Yamaguchi prefectures and Iki and Tsushima islands in Nagasaki Prefecture

• Red heavy snow warnings: Southern Nagano Prefecture

• Red high wave warnings: western Ehime, Ishikawa, northern and central Oita, and eastern Yamaguchi prefectures and southern Izu Islands in Tokyo Prefecture

• Yellow warnings: 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.

The storm could produce rounds of heavy precipitation (including rain and snow), strong winds, and isolated thunderstorm activity. 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 and in urban areas with easily overwhelmed stormwater drainage systems. Sites downstream of large reservoirs may be subject to flash flooding after relatively short periods of intense rainfall.

Precipitation could fall as snow in the higher elevations over the coming days. Wind gusts could cause blowing and drifting snow; decreased visibility is likely in mountainous areas. Rain-induced landslides are possible in areas of elevated terrain; there is also the possibility of avalanches in mountainous areas where the snowpack has become unstable due to heavy snowfall. Power outages could occur throughout the affected area. 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. Mountain passes and tunnels could be closed as a precautionary measure during periods of intense snowfall.

The disruptive weather will likely cause delays and cancellations at regional airports. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding/snow could block regional rail lines; freight and passenger train delays and cancellations are possible in areas with heavy rainfall and potential track blockages.

Disruptions triggered by inclement weather and resultant hazards, such as flooding or avalanches, could persist well after conditions have improved - it could take days before any floodwaters recede and/or officials clear debris. Repair or reconstruction efforts may result in residual disruptions if there is severe damage to infrastructure.