“With a La Niña climate pattern in place, southern parts of the U.S. may experience expanded and intensifying drought during the winter months ahead,” according to the National Oceanic and Atmospheric Administration, the agency that issued the forecast, which covers the months of December, January, and February.
La Niña – a natural climate pattern marked by cooler-than-average water in the central Pacific Ocean – is one of the main drivers of weather around the world, especially during the late fall, winter and early spring.
“With La Niña well established and expected to persist through the upcoming 2020 winter season, we anticipate the typical, cooler, wetter North and warmer, drier South as the most likely outcome of winter weather that the U.S. will experience this year,” Mike Halpert, deputy director of NOAA’s Climate Prediction Center, said in a statement.
La Niña is the opposite pattern of the more well-known El Niño, which features warmer-than-average water in the central Pacific Ocean.
Two parts of the country that should see below-normal temperatures this winter are the northern Plains and the Pacific Northwest, NOAA said. Those areas, along with the Great Lakes and the Ohio Valley, should see more rain and snow than usual.
This winter forecast does not specify how much precipitation will fall as rain, snow or ice, only that more or less is likely overall. Snow forecasts depend upon the strength and track of winter storms, which generally cannot be predicted more than a week in advance, the center said.
Halpert said La Niña winters tend to not feature the blockbuster East Coast winter storms or blizzards that can paralyze the big Northeastern cities. That’s more likely with El Niño, he said, but extreme events are not something meteorologists can see in seasonal forecasts.
Other large-scale climate patterns in the atmosphere aren’t included in this official forecast since they can’t be predicted more than one or two weeks in advance.
These include the Arctic Oscillation and the North Atlantic Oscillation, which influence the number and intensity of arctic air masses that overspread the central and eastern USA.
Halpert said he doesn’t expect the dreaded polar vortex to be much of a factor this year, except potentially in the northern Plains and Great Lakes.
La Niña also dominates the forecast by private company AccuWeather: mainly dry in the South, wet and snowy in the Pacific Northwest, bouts of snow and rain from Minneapolis through the Great Lakes region, big swings in the heartland, and mild weather in the mid-Atlantic.