The potential for heavy rain and severe thunderstorms will exist through much of this week across central South America. Argentina, Uruguay, Paraguay, and southern Brazil are the countries most at risk for damaging thunderstorms and flooding rain.
The Setup
High pressure will setup to the east of Uruguay this week while low pressure will establish itself over the Gran Chaco region located just east of the Andes Mountains. Additionally, a second low pressure system will move into Chile later in the week.
The flow around the pressure systems will draw tropical moisture southward. The result will be numerous rounds of showers and heavy thunderstorms, some of which will be severe.
Initially, the heaviest rain and best chance for severe thunderstorms will exist across Paraguay and central Argentina through Tuesday. However, this threat area will shift toward eastern Argentina, Uruguay, and southern Brazil during the middle and end of the week.
The Impacts
Damaging winds, large hail, and torrential downpours capable of flash flooding are likely in the heaviest storms.
5-day rainfall totals of 100-200 mm are likely in a corridor from northern Argentina into parts of Paraguay. Outside of this area, widespread rainfall amounts of 25-100 mm are likely.
Weather models trends this weekend suggest that the period from Wednesday evening through Thursday and Thursday night may bring the greatest risk for severe thunderstorms and flash flooding.
Capital cities such as Asuncion, Buenos Aires, and Montevideo are within the threat area for heavy rain and severe storms, mainly from Tuesday through Thursday night. Other cities such as Cordoba and Rosario are also at risk for severe weather and flash flooding.
By the upcoming weekend, the risk for severe weather will end as a more tranquil fall air mass moves into the region.