2017-2018 La Niña and winter outlook
BROOKINGS — The National Oceanic Atmospheric Administration’s (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,” said Laura Edwards, SDSU Extension state climatologist.
NOAA observes La Niña conditions using sea surface temperatures in the Pacific Ocean, Edwards explained. “For La Niña, ocean temperatures are cooler than average near the equator in the Pacific Ocean, which can alter jet streams and storm tracks,” she said.
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,” Edwards said. “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, Edwards said a weak La Niña is expected. “Thus the climate outlook shows an increased chance of above average precipitation,” she explained.
This potential increase is snowfall is more likely to occur 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,” Edwards said.
La Nina’s impact on agriculture
This cold, and possibly wet, climate outlook may create challenges for South Dakota’s 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,” Edwards said.
Shelter and protection from severe cold and some increased snowpack amounts may need to be considered as well.
Winter wheat growers may take some solace in the potential for increased snowfall, as this can insulate the crop in harsh cold temperatures. Also, increased snowfall can provide some soil moisture in the spring when it comes out of dormancy.