Through Wednesday, a series of low pressure systems will traverse central South America bringing locally flooding rainfall to Southeast Brazil, northeast Argentina and eastern Paraguay.
Low pressure will cause rain to turn heavy at times on Sunday night across far southeast Paraguay, the Brazilian state of Rio Grande do Sul and the Argentinian province of Misiones. On Sunday night, 25-75 mm (1-3 inches) of rain will lead to the risk for flash flooding.
This first wave of heavy rainfall shifts to the north on Monday causing showers and thunderstorms to spread as far north as Rio de Janeiro by afternoon. Locally heavy rainfall may lead to flooding in these areas; however, AccuWeather.com Meteorologists feel that the flooding threat will not be as widespread compared to farther south.
The second in a series of low pressure systems will enhance rainfall once again on Monday night and into Tuesday from far southeast Paraguay into Rio Grande do Sul. Additional rainfall of 25-75 mm (1-3 inches) is expected with this second round of rainfall.
Because the ground will already be saturated from the first round of rain, additional heavy rain could lead to more widespread flooding concerns.
So far this September, rainfall across the region has been above average with some areas receiving twice their normal rainfall.
By Wednesday, high pressure begins to build across eastern Argentina which will bring heavy rainfall to an end, but a few showers and thunderstorms will still remain. More widespread dry conditions are expected on Thursday.