Southeastern Brazil and surrounding areas are forecast to experience another heavy precipitation event

It is forecasted that from the June 26th to June 30th, under the influence of an eastward-moving and deepening upper-level trough (Fig. 1), central-southern South America is expected to experience a significant weather event characterized by strong winds, a sharp temperature drop, rain, and snow. Chile, Argentina, Bolivia, Paraguay, and surrounding areas will experience a temperature drop of 6-8°C progressing from south to north. High-altitude mountainous areas will see drops of 10-12°C. This will be accompanied by winds of Force 4-6 Beaufort scale with gusts around Force 7. In the high-altitude mountainous areas of Chile and Argentina, gusts will reach Force 8-10 (Fig. 2). Central-southern Chile, southern Argentina, and high-altitude mountainous areas are forecast to receive moderate to heavy snow or sleet, locally heavy to severe snowstorms. Moderate to heavy rain is forecast for southeastern Brazil, northeastern Argentina, eastern and southern Paraguay, and southern Uruguay. Within this region, parts of Santa Catarina state and northern Rio Grande do Sul state are expected to experience heavy to torrential rain.Accumulated rainfall across the aforementioned areas is predicted to reach 30-80 mm, locally exceeding 120 mm (Fig. 3). This precipitation will be accompanied by short-duration heavy rainfall and other severe convective weather. The peak intensity of the rainfall is expected on 29 June. Due to significant overlap between the forecast precipitation zone and areas affected by recent rainfall events, combined with locally intense rainfall carrying extreme characteristics, heightened vigilance is required against secondary disasters such as landslides and flooding in low-lying areas.

Figure 1. Geopotential Height Field at 500 hPa(Contour, Unit: dagpm) and Wind Field at 850 hPa (Wind Barbs, Unit: m/s) at 1200 UTC June 26, 2025

Figure 2. Forecast of Maximum Gusts in 24 Hours on June 26, 2025 (Shaded, Unit: m/s)

Figure 3. Forecasted Accumulated Precipitation from June 26 to 30, 2025 (Unit: mm)

Author: Huo Da                                 Reviewer: Niu Ruoyun 

English reviewer:Wang Yi                                                                       Issue approver:Dai Kan