While much of Argentina and Chile has experienced record rain and snowfall over the last several days, conditions could not be more different to the north and east. Paraguay, Bolivia, Brazil, and Peru experienced record warmth, while numerous wildfires burned in Argentina. Read on for more details. 

Over the a five day stretch this week, Las Lenas piled up over 4m meters of snow and Portillo received more than 2.7 meters. Below is an image of the recent snow in the Mendoza Mountains of Argentina. 

In the lower elevations of Chile, several twenty-four-hour rainfall records were broken, with numerous areas receiving more than 150 mm of rain and up to 800 mm in spots. Check out a few shots of some road damage and flooding below in Chile. 

Meanwhile, not far away, a very different type of extreme weather event was happening in Paraguay, Peru, Brazil, and Bolivia. 

Both Paraguay and Bolivia recorded their hottest Winter day on record yesterday, at 45 C (113 F) and 41.9 C (107  F) respectively. The 45 C recorded at Villamontes in Bolivia is the highest temperature ever recorded during meteorological winter in the entire Southern Hemisphere.

The image above shows the temperature anomalies (departure from normal) for Wednesday 8/23.

Brazil and Peru broke winter heat records also, with temperatures reaching 41.4 C in Jacarepagua and 40 C in Puerto Ocopa respectively. 

In Argentina, dozens of wildfires burned on Tuesday, especially in the San Luis and Cordoba regions. The satellite images that follow are zoomed in on this region in northern Argentina. 

You can see several fires their smoke plumes in the Cordoba and San Luis regions, and countless others shown in red in the other provinces. 

Below we have zoomed in even further on the Cordoba and San Luis regions of Argentina, with the fires shown in red and their smoke plumes moving to the east.

While wildfires are common in northeastern Argentina during the Winter, the contrast with the record heat, numerous fires, and the atmospheric river-driven massive snowfall is striking. 
To understand why these contrasting weather events occurred simultaneously and in close proximity, we need to examine the formation of atmospheric rivers and their ability to penetrate inland. 

Atmospheric rivers often form along temperature gradients, which are typically found between warm, moisture-rich regions in the tropics or subtropics and cooler regions farther poleward. The temperature contrast between these two regions creates favorable conditions for the development of these narrow corridors of intense moisture transport in the atmosphere. 

Further, the extent to which atmospheric rivers penetrate inland depends on several factors, including the strength of the atmospheric river, the topography of the region, and the prevailing weather patterns. In this case, the orientation of the atmospheric river played an important role as well.

The atmospheric river was quite strong, delivering record rain on the windward side of the Andes and massive snowfall at upper elevations. However, on the leeward side of the Andes, dry air inhibited further inland penetration. Additionally, the atmopsheric river was oriented in a northwest to southeast direction, and for the majority of the long-duration event, the narrow plume of moisture was south of the wildfires shown above.

As a result, we are able to see intense snowfall at upper elevations due to the atmospheric river, anomalously warm temperatures on the equatorward side of the temperature gradient, and wildfires continuing to burn all at the same time. 

Luke Stone
Forecaster, OpenSnow