La Niña is Coming!
The NOAA Climate Prediction Center has officially declared a La Niña Advisory, as of November 9, 2017. This means that La Niña conditions are observed and expected to continue. They observe La Niña conditions using sea surface temperatures in the Pacific Ocean and if weather patterns in the atmosphere are changing due to the ocean temperatures. For La Niña, ocean temperatures are cooler than average near the equator in the Pacific Ocean, which can alter jet streams and storm tracks.
What to Expect
Historically, La Niña has brought colder than average temperatures in winter for South Dakota. There are varying strengths of La Niña, from weak to strong. Overall the colder temperatures are fairly consistent in any La Niña winter. What is more variable is snowfall.
In weak La Niña events, there has historically been above average snowfall in the Northern Plains states. In strong La Niña events, this is not usually the case. For our winter season ahead, a weak La Niña is expected, and thus the climate outlook shows an increased chance of above average precipitation. This potential increase is snowfall is more likely in mid- to late winter, or around January and February of 2018.
Despite the very dry November, there was recently a large pattern shift in early December, which is now starting to look more like a typical La Niña pattern. This will put South Dakota near the jet stream path, bringing colder air down from Canada and possibly some more chances of precipitation in the next couple of weeks.
This cold, and possibly wet, climate outlook may be a challenge for livestock producers who have already struggled with drought losses in pastures and forage. One way that animals adapt to severe cold is to increase their feed intake, which is already a challenge in some areas. Shelter and protection from severe cold and some increased snowpack amounts may need to be considered as well.
Winter wheat farmers may take some solace in the potential for increased snowfall, as this can insulate the crop in harsh cold temperatures, and also provide some soil moisture in the spring when it comes out of dormancy.
Figure 1. Precipitation outlook for December 2017 to February 2018. The La Niña pattern brings increased chances of colder temperatures and wetter conditions, as compared to the long-term average.
Source: NOAA Climate Prediction Center