Daily downpours are expected to slam parts of Argentina and Uruguay through the weekend and early next week, with the risk for dangerous flooding.
A slow-moving cold front will cross the Rio de La Plata on Friday and stall over Uruguay over the weekend. This front will be the focal point of dangerous downpours during this time.
Thunderstorms are expected to ignite Friday across the province of Buenos Aires and Entre Rios as well as southern Uruguay. These storms will bring the threat for damaging winds up to 90 kph (55 mph) and torrential downpours that can lead to flash flooding.
Buenos Aires and Rosario, Argentina, as well as Montevideo, Uruguay, will be in the threat zone from these storms.
As these storms coalesce Friday night, the main threat will turn to flash flooding. These storms are expected to be north of Buenos Aires by Friday night but they could hold on longer in Montevideo.
Strong winds aloft will pull in tropical moisture which will provide the fuel for downpours and flash flooding. The heaviest storms will be capable of unloading 25 to 50 mm (1 to 2 inches) of rain in an hour's time.
"The biggest threat will be training thunderstorms, or thunderstorms that repeat over a certain area," AccuWeather Meteorologist Jim Andrews said.
"This can give locations very large rainfall amounts in a span of only a few hours, a situation that can be life-threatening," he warned.
Downpours will continue to focus along the front Saturday and Sunday with isolated strong wind gusts. Motorists may find difficulty traveling during the heavy rain. Lowered visibility, flooded roadways and wind gusts will slow travel and create delays.
"In addition to flash flooding, there will be some isolated incidents of damaging wind gusts and perhaps even hail," Andrews said. "An isolated tornado is not out of the question but the probability is low."
Those with outdoor plans this weekend in these areas will want to reconsider scheduling them for later next week.
Rainfall totals by the end of the weekend may range between 3 and 6 inches across parts of Uruguay and Argentina with higher amounts locally.
Rain will likely continue into early next week across Uruguay and northeastern Argentina with the front remaining in the area.
The front will weaken and move away by the middle of the week.
Some places in Uruguay and eastern Argentina have received above-average rainfall since March. Buenos Aires experienced a drier-than-normal month of March, but April has started off wetter than normal. Montevideo is running nearly 2 inches above normal in terms of rainfall since March.
The recent above-average rainfall seen across the region will increase the threat for dangerous flooding as streams and rivers are already running above normal and soil moisture is slightly higher.