A new cold front linked to an extratropical cyclone forming near Uruguay has placed all three states of Southern Brazil on high alert for severe storms, hail, and tornadoes. The warnings were issued by the Rio Grande do Sul Civil Defense, Santa Catarina state weather service Epagri/Ciram, and the National Institute of Meteorology (Inmet), as reported by Folha de S.Paulo.

In Rio Grande do Sul, rainfall is expected to reach up to 100 millimeters within 24 hours on Thursday, with cumulative totals surpassing 150 millimeters through Friday. State authorities warned of wind gusts reaching 90 km/h across northern and western areas, as well as along the border with Uruguay, creating atmospheric conditions ripe for hail and tornadoes.

The heavy rainfall poses an immediate threat to river basins across Rio Grande do Sul. Flooding risks are highest along the Uruguay River, spanning from the northwest to the western border. Meanwhile, state emergency teams are closely monitoring rising water levels on the Caí, Sinos, Taquari, Ibicuí, and Ibirapuitã rivers, though none of those five basins are currently forecast to spill their banks.

As the low-pressure system intensifies, bad weather is spreading northward. In Santa Catarina, Epagri/Ciram issued alerts for destructive winds and hail in northern and western municipalities. By Friday and Saturday, the storm system is projected to cover almost the entirety of Paraná state, where Inmet issued severe storm warnings.

The frequent recurrence of extratropical cyclones and violent convective storms over the Southern Cone is tied to sharp thermal clashes between tropical air masses and polar fronts, intensified by warming patterns across the South Atlantic. State and municipal civil defense agencies have mobilized emergency response units and activated cell broadcast warnings, urging residents in flood-prone and rural communities to secure shelter and avoid crossing swollen roadways.