A front lifting through eastern South America threatens to bring flooding from Uruguay to southeastern Brazil late this weekend into early next week.
A slow-moving cold front moving north in the region will be the instigator, bringing major changes from Argentina to southern Brazil. Showers and thunderstorms concentrated along that front will train and move little, bringing the potential for a significant amount of rain in a short period of time.
The front will be slowest near the border of Uruguay and Brazil on Sunday and Monday. A widespread 1-2 inches (5-10cm) of rain is possible across this region, bringing the risk for flash flooding.
The front will reach peak intensity further north after moving into the southeastern Brazil and into far northeastern Argentina. Rainfall amounts there are expected to be between 2-4 inches (10-20cm), bringing the greatest risk of flash flooding along the path of the front.
AccuWeather.com Meteorologist Anthony Sagliani says the worst flooding is expected in Rio Grande Do Sul, and that in particular low lying and poor drainage areas are of the most concern. According to him "The slow moving nature of the front really opens up the possibility to overwhelm some of these poor drainage areas, where rain will outpace efforts to remove it.
On Tuesday low pressure forming along the front will work to pull it offshore, bringing an end to the heavy rain threat. By Wednesday high pressure will have returned to the region, bringing back settled weather.
Despite the flooding the rain may bring potential benefits to parts of the region by helping to bring the region back up towards normal. Many parts of the region are running behind on rainfall this July. Pelotas, Brazil has only seen 61 percent of normal so far this month, for example.
Behind the front, cooler conditions can be expected early next week, especially across northern Argentina and Uruguay. Warm conditions will wait until midweek to return.