A strengthening storm system emerging from the Andes on Sunday will cause thunderstorms to develop from northern Argentina into western Uruguay.
More isolated thunderstorms can develop as far north as Asuncion, Paraguay, by the end of the day.
These thunderstorms will be capable of producing torrential rainfall, damaging winds and hail.
The heaviest rainfall through Sunday night is expected across northeastern Argentina, western Uruguay, southeastern Brazil and southern Paraguay.
These areas can expected 25-75 mm (1-3 inches) of rainfall with local amounts exceeding 100 mm (4 inches).
On Monday, the heavy rain and storms will track across northern Uruguay and southeastern Brazil.
The heaviest rainfall will avoid Buenos Aires, Argentina, and Montevideo, Uruguay, this time. However, both cities can get rain and a gusty thunderstorm Sunday evening into Sunday night.