A storm system emerging from the Andes on Tuesday will produce widespread heavy rainfall and thunderstorms across far northern Argentina, Paraguay and southeast Brazil through Wednesday night.
The storms will develop during the day Tuesday over northern Argentina and then shift north and east Tuesday night and Wednesday.
Heavy rain will be the biggest threat from these storms, although strong winds will also accompany the strongest storms.
Rainfall amounts of 50-100 mm (2-4 inches) will be common from far northeast Argentina and southern Paraguay into northern Rio Grande do Sul and Santa Catarina. Local rainfall amounts up to 200 mm (8 inches) are possible.
Rainfall of this magnitude will lead to widespread flooding threats across the region as most of the rain will fall within a 12- to 18-hour period.
Cities included in this flooding threat are Asuncion and Ciudad del Este in Paraguay, Posadas in Argentina and Caxias do Sul in Brazil.
By Thursday any lingering thunderstorms will shift farther north across Brazil, but the threat of flooding rainfall will have ended.