South America Calling

High pressure kept showers limited across Argentina this week and there has been some concerns about dryness in southeastern growing areas like the province of Buenos Aires. Buenos Aires produces approximately 27% of the corn crop in Argentina and 31% of the soybeans. Even though they have had drier-than-normal conditions during the past seven days, a front could offer more widespread showers next week.

Looking at a map of average precipitation from the past 30 days across South America, it shows a peppering of isolated spots that have both below- and above-average precipitation across Argentina's provinces. Cutting that down to the past seven days, the map looks a lot different. Below-average precipitation extends through much of Buenos Aires, but farther north in Santa Fe and Cordoba, there's an extensive area of above-average precipitation extends through these two provinces.

Even with precipitation being below normal during the past week across Buenos Aires, is it time to start worrying about drought and its impact on the corn and soybean crop? If next week's forecast pans out, we could stave off drought concerns for another week.

On Dec. 29, the European model (ECMWF) has a small cluster of showers forming in southern Buenos Aires during the day as the system rides along the northern edge of high pressure. The ECWMF predicts up to 10-15 millimeters (0.4-0.6 inches) of rain across south-central Buenos Aires on Sunday. This is a much different picture when compared to the American GFS, as the GFS only suggests about 1 mm (0.04 inches) of rain for south-central Buenos Aires and the coverage of the showers is much less.

Luckily, even if models can't agree on Sunday's rainfall potential, they agree that a front will slowly progress from southwest to northeast across Argentina from late Monday into Thursday. As the front moves through the country, it should provide widespread showers throughout much of Buenos Aires, Cordoba and Santa Fe. Some of the showers could produce rainfall totals near 30-40 mm (1.2-1.6 inches) by the time the front exits on Thursday. Thunderstorms will likely be dispersed amongst the showers and could offer locally higher rainfall totals near 2 inches.

Temperatures have also been favorable this week for the developing crops as they have largely been below average. High temperatures on Christmas Eve and Christmas Day reached 20-28 degrees Celsius (68-82 degrees Fahrenheit) across the main growing areas of Argentina. These lower temperatures aren't as likely to dry out topsoil as compared to high temperatures in the 30s or even lower 40s C (85-105 F). By next week, temperatures behind the cold front will take another dive below average. DTN isn't forecasting temperatures to start rising above average until the second week of January.

Both early planted soybeans and soybeans planted in December will greatly benefit from next week's showers, even if the precipitation amounts are still below average. Consistent rain showers start becoming more important by late January into February when most of the soybean crop will be flowering, and dryness and heat are much more of a concern. For now, a few stretches of drier weather aren't too concerning.

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Teresa Wells can be reached at teresa.wells@dtn.com

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