Chile, Argentina: Adverse weather forecast across central regions through at least June 22 /update 1

Thunderstorms are forecast across parts of central Chile and central Argentina through at least June 22. Heavy rainfall, strong winds, and lightning may accompany storms. Heavy downpours may trigger flooding in low-lying areas, and strong winds could cause property damage and power outages.

As of late June 20, the Chilean Meteorological Directorate has issued the following weather warnings across the affected area:

• Red rainfall warnings (the highest level on a three-tier scale): Valparaiso, Metropolitan, and O'Higgins regions through June 21; up to 5.5 cm (2 inches) of rainfall is forecast.

• Orange rainfall warnings: Valparaiso, Metropolitan, O'Higgins, Maule, and Nuble regions through June 22.

• Orange strong wind warnings: Biobio, Maule, and Nuble regions through June 21.

• Yellow thunderstorm, rainfall, and strong wind warnings: Across the rest of the affected area through June 22.

The Argentina National Meteorological Service (SMN) has issued the following weather warnings across the affected area:

• Orange snow warnings (the middle level on a three-tier scale): Parts of southern Chubut, southwestern Mendoza, northwestern Neuquen, and eastern Santa Cruz provinces through June 21.

• Yellow snow and strong wind warnings: Across the rest of the affected area through June 22.

Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

Authorities in Biobio Region, Chile, have issued evacuation orders for the areas surrounding the Curanilahue and Ranas rivers and the Las Plegarias estuary due to the flooding of the river basins. Evacuation orders are also in place for the Millahue sector, San Vicente de Tagua Tagua Commune, O'Higgins Region, due to the threat of flooding of the Tranque River.

Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed stormwater drainage systems. Sites downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides are possible in hilly or mountainous areas, especially where heavy rainfall has saturated the soil.

Authorities could issue mandatory evacuation orders for flood-prone communities over the coming days. Disruptions to electricity and telecommunications services are likely where significant flooding, landslides, or strong winds impact utility networks.

Floodwaters and debris flows will likely render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters. The disruptive weather may cause some delays and cancellations at airports in the affected regions. Flooding could block regional rail lines; freight cancellations are possible in areas with heavy rainfall and potential track blockages.

Localized business disruptions will likely occur in areas impacted by severe weather; some businesses might not operate at full capacity because of damage to facilities, possible evacuations, and some employees' inability to reach work sites.