Flooding downpours may sweep from northern Argentina to southern Brazil this weekend

By Kristina Pydynowski, AccuWeather senior meteorologist

November 16, 2018, 1:30:54 PM EST

Drenching thunderstorms may do more than ruin weekend plans across central South America. Flash flooding can be triggered in some communities from northern parts of Argentina and Uruguay to southern Brazil.

After the weekend starts with heavy rain soaking the Argentina provinces of Buenos Aires (south of the capital city) and La Pampa, drenching thunderstorms are expected to ramp up across northernmost Argentina, northern Uruguay and the Brazilian state of Rio Grande do Sul during the day on Saturday.

Downpours will then sweep northward across more of southern Brazil, Paraguay and Bolivia Saturday night into Sunday.

Cities in the path of the heavy thunderstorms include Corrientes and Reconquista in Argentina, Rivera in Uruguay, Asunción in Paraguay and Santa Maria and Campo Grande in southern Brazil.

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"The main concern from the heavy thunderstorms will be flash flooding, but a few thunderstorms can produce damaging winds," according to AccuWeather Senior Meteorologist Rob Miller.

Low-lying, poor drainage and urban areas are most susceptible to flash flooding, especially where recent heavy rain has left the ground saturated. Small streams and rivers can also overflow their banks.

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Where gusty winds are kicked up, trees sitting in the soggy ground can be more easily downed and cause local property damage and/or sporadic power outages.

Even in the absence of flooding, motorists should use caution. Downpours can reduce visibility and heighten the risk of vehicles hydroplaning when traveling at highway speeds.

"While the more widespread downpour threat will exist to the north, localized downpours can still dampen Buenos Aires, Argentina, and Montevideo, Uruguay, and reduce visibility for motorists on Saturday,” Miller said.

Be sure to seek shelter as soon as thunder is heard; the risk of being struck by lightning is then present.

Sunday will be the much nicer day of the weekend for outdoor activities in these cities as sunshine dominates.

Warm-weather fans in Montevideo may opt for a light jacket before heading outside, especially in the morning. A breeze will usher in the cooler air that will hold Sunday's high to around 20 C (upper 60s F). A high closer to 23 C (lower 70s) is more typical of mid-November.