Two powerful atmospheric rivers are forecast to strike South America this week, bringing extreme rainfall, severe storms, and heavy mountain snowfall across Chile, Argentina, Uruguay, and Southern Brazil. According to data from MetSul, these moisture corridors—some reaching category 4 and 5 intensity—threaten to trigger flash flooding and significant infrastructure disruption across the continent.
The Pacific Corridor: Extreme Impact on Chile
A high-intensity atmospheric river originating in the Pacific Ocean is targeting Central Chile, with the Direção Meteorológica do Chile (DMC) issuing urgent weather alerts. Meteorologists classify this as one of the most significant meteorological events in the region in recent years, with the potential to dump up to 300 mm of rain in specific sectors like Valparaíso.
The moisture will hit the Biobío, La Araucanía, and Los Ríos regions before advancing toward the Metropolitan Region, Valparaíso, and Coquimbo. Projections from the DMC indicate that the most severe volumes will occur between Wednesday and Thursday, particularly in San Fabián de Alico, Cobquecura, Coihueco, and Antuco, where rainfall could reach 200 mm.
Pro Tip: Mountain travel across the Andes is expected to be hazardous. Heavy snow accumulation will likely close international passes, significantly reducing visibility and complicating logistics between Chile and Argentina.
The Continental Corridor: Southern Brazil and Argentina
A second atmospheric river is forming within the interior of South America, fueled by an intense low-level jet stream. This system is transporting warm, tropical air from Bolivia and Brazil’s Center-West toward the continent’s mid-latitudes, impacting Argentina, Uruguay, and the South of Brazil starting Thursday (16) and Friday (17).
MetSul reports that this system will act as a “warm front” initially, bringing severe thunderstorms, hail, and high wind gusts. By the weekend, the front is expected to become semi-stationary between Rio Grande do Sul and Santa Catarina. In some areas, rainfall totals are projected to reach 200 mm to 300 mm by mid-next week—potentially doubling the entire monthly average for July in a matter of days.
Understanding Atmospheric Rivers
An atmospheric river is a long, narrow region in the atmosphere that transports water vapor from tropical regions to higher latitudes. When these “rivers” collide with mountainous terrain or low-pressure systems, the air is forced upward, where it cools and condenses into intense precipitation.
According to MetSul, the intensity of these events depends on the volume of moisture available and the speed of atmospheric circulation. While they are a natural part of the climate, extreme events can lead to widespread flooding, landslides, and, in higher altitudes, massive snowdrifts that can isolate rural communities for days.
Government Response and Public Safety
Authorities in Chile have mobilized emergency services, including the military and fire departments, to prepare for potential flooding and structural damage. In a preventive measure, the Chilean Ministry of Education has suspended classes for Friday in several regions, including Coquimbo, Valparaíso, the Metropolitan Region, O’Higgins, and Maule.
Frequently Asked Questions
- What is an atmospheric river? It is a concentrated, narrow channel of water vapor in the sky that acts like a river, transporting moisture thousands of miles from the tropics.
- Why are these systems dangerous? They can produce days of continuous, heavy rain or snow, leading to flash floods, landslides, and the closure of critical transportation routes.
- How long will the rain last? In some regions, such as Santiago, Chile, models suggest up to seven consecutive days of precipitation if the sequence of frontal systems remains active.
Stay Informed: Weather patterns can shift rapidly. For real-time updates on your specific region, please check your local meteorological office’s official alerts. Have you experienced an atmospheric river event in your area? Share your story in the comments below.