NOAA forecasters are predicting a mild and dry winter ahead for the southern tier of the United States, including already drought-stricken areas in the lower Mississippi River Valley and the Southwest, with cooler- and wetter-than-normal conditions expected in the Pacific Northwest and around the Great Lakes.
It is a discouraging outlook for areas already stressed by prolonged drought, and could elevate wildfire dangers in parts of the south-central U.S. that don’t normally face such dangers. Extended and exacerbating dry conditions are likely in the Southwest as well as states like Kansas and Oklahoma, which are experiencing extreme and in many cases exceptional drought, according to the U.S. Drought Monitor.
That could mean continuing concerns about the Mississippi River, where low water levels are making it difficult to move cargo via barges. Climate forecasters predict developing drought in the lower Mississippi Valley and seasonally dry conditions across the Missouri River basin, though drought conditions could ease along the Ohio River.
And it means no slowing in the momentum of a megadrought in California and the West, with no relief for the parched Colorado River basin and dangerously depleted Southwest reservoirs like Lake Mead and Lake Powell.
“Part of the reason for the persistent [drought] forecast is La Niña, but also just the long-term nature of the drought,” said Brad Pugh, a meteorologist at NOAA’s Climate Prediction Center.
According to the drought monitor’s latest weekly report, more than 80 percent of the continental U.S. is experiencing at least abnormally dry conditions, if not drought, the largest proportion since the reports began in 2000.
“Drought conditions are now present across approximately 59% of the country, but parts of the Western U.S. and southern Great Plains will continue to be the hardest hit this winter,” Jon Gottschalck, chief of the climate center’s operational prediction branch, said in a statement. “With the La Niña climate pattern still in place, drought conditions may also expand to the Gulf Coast.”
On the other hand, winter precipitation is forecast to be even heavier than normal in the Pacific Northwest, and storm systems could also deliver above-normal precipitation to the Great Lakes region, according to the forecast.
Relatively mild and dry conditions are also expected to extend up the Interstate 95 corridor on the East Coast, meaning cities from Washington to Boston are likely to find themselves close to the line between rain and snowfall for any storms that move up the coast, Gottschalck said.
Seasonal forecasting can be a challenge for meteorologists because the key weather prediction models they use are designed for relatively short-term prognostication. Forecast accuracy breaks down more than about a week in advance, so for predictions like the ones NOAA released Thursday, scientists rely largely on signals from global climate patterns like La Niña.
In some years, seasonal forecasting can perform worse than a random guess.
In the United States, La Niña is known for creating warm and dry conditions across the southern tier of the country, with cooler- and wetter-than-normal conditions along its northern tier, including in the Pacific Northwest and Midwest. That’s because it tends to shift the jet stream — a band of atmospheric winds that steers weather systems across the continent — toward northern states and Canada.
Despite the influence of La Niña, Gottschalck said there is significant uncertainty in weather patterns for much of the middle of the country, where forecasters predict equal chances of cold or mild conditions and dry or wet patterns. La Niña can allow for considerable “week-to-week variability,” as shown by the extreme cold that spread across the country and caused an energy crisis in Texas in February 2021, he said.
In the winter of 2020-2021, the current stretch of La Niña had just begun, and yet the season was marked by historic cold across the contiguous United States. The polar vortex, a column of frigid air that typically remains contained over the North Pole region, came spilling southward and produced some of the snowiest winters on record across the Deep South.
Still, NOAA’s forecast for this winter closely matches graphics used to depict classic La Niña conditions. Gottschalck said that while NOAA uses some long-range forecasting models to guide its predictions, typical expectations of La Niña do “serve as a first guess.”
La Niña’s impacts around the world include dry conditions in Peru, Chile and the Horn of Africa, and heavy rainfall over southeast Asia and Australia. The U.S. Climate Prediction Center expects a 75 percent chance that La Niña will continue at least through the winter.
This year, NOAA’s predictions are in line with other conventional thinking, including seasonal forecasts released by AccuWeather and the Weather Channel that call for continued La Niña influence on weather patterns.