Heat will build across northern Argentina, Uruguay, southern Brazil and Paraguay the next few days, setting the stage for a powerful cold front to bring much cooler air, strong thunderstorms and flooding downpours this weekend.
Temperatures will climb into the low to mid-30s C (88-94 F) on Friday in Buenos Aires, Argentina, and Montevideo, Uruguay. The heat will peak in Porto Alegre, Brazil, and Asuncion, Paraguay, on Saturday.
Temperatures will fall dramatically behind the cold front as it lifts northward Friday through Sunday. Temperatures are expected to be 6-12 C (10-20 F) cooler behind the front across the entire region.
This powerful front will also spark strong thunderstorms across northern Argentina, putting Buenos Aires, Cordoba and Rosario late Friday night into Saturday.
As the front moves farther north, thunderstorms will bring the threat for widespread heavy rainfall which may produce flooding from far northern Argentina into eastern Paraguay, northern Uruguay and southeastern Brazil. Major cities that may experience flooding include Asuncion in Paraguay, Posadas in Argentina and Porto Alegre and Curitiba in Brazil.
Rainfall totals of 50-100 mm (2-4 inches) are expected along with locally strong winds and small hail.
As this front moves to the north, high pressure will build into Argentina to provide a stretch of dry weather that will last from Monday through Friday.