Oct. 18 (UPI) -- The odds are in favor of a milder winter for much of the United States, according to the latest seasonal outlook from the National Weather Service.
Forecasters predict a warm, wet winter for much of the American South, while mild but dry weather is expected across much of the American West and some parts of the North. The predictions are largely based on the expected formation of El Niño.
The El Niño Southern Oscillation, ENSO, describes a periodic variation in winds and sea surface temperatures in the central and eastern equatorial Pacific. The irregular variability features two main patterns: a warming pattern, El Niño, and a cooling pattern, La Niña.
Currently, NWS scientists predict a 70 to 75 chance of an El Niño pattern.
"We expect El Niño to be in place in late fall to early winter," Mike Halpert, deputy director of NOAA's Climate Prediction Center, said in a news release. "Although a weak El Niño is expected, it may still influence the winter season by bringing wetter conditions across the southern United States, and warmer, drier conditions to parts of the North."
Above average temperatures are most likely in the Pacific Northwest, while wetter-than-normal weather is most likely across the Deep South.
Other atmospheric patterns can influence weather patterns. But the Arctic Oscillation, which influences the movement of arctic air masses, and the Madden-Julian Oscillation, which can bring larger winter storms to the West Coast, are more variable and harder to predict.
Predicting snowstorms is also difficult, which is why NOAA's Winter Outlook focuses on seasonal temperature and precipitation averages, not snowfall totals.
"Even during a warmer-than-average winter, periods of cold temperatures and snowfall are still likely to occur," according to NOAA.