Whether you'll experience a dry, mild winter or a wet, cold one will be all about the seesaw dance of warmer and cooler seawater in the tropical Pacific Ocean that produces the climate effects known as El Niño and La Niña, government forecasters said Thursday.

This year a dry, mild winter is likely across most of the southern U.S., thanks to a developing La Niña, but the northern tier of the nation could get walloped by a colder and wetter winter, the forecasters said.

NOAA Winter Outlook (NOAA)

Another winter forecast, released this week by the private firm Atmospheric and Environmental Research, said colder than normal temperatures are expected for much of the eastern U.S. and warmer than normal temperatures are likely in the West.

Forecasters at NOAA’s Climate Prediction Center issued their official U.S. winter outlook Thursday, saying that La Niña is expected to influence winter weather across the U.S. this year.

La Niña is the cool counterpart to El Niño, which dominated the winter of 2015-16. The entire natural climate cycle is officially known as the El Niño – Southern Oscillation (ENSO), the swings between warmer and cooler seawater in the tropical Pacific Ocean. ENSO is the primary factor that government scientists consider when announcing their winter weather forecast.

This forecast only predicts where above or below normal temperatures — and above or below normal precipitation — are most likely. It does not predict how much snow will fall, or the severity or length of cold snaps.

The Atmospheric and Environmental Research forecast looks at a variety of climate factors in addition to ENSO, including how much snow is on the ground in Siberia in October and the extent of Arctic sea ice in September.

The La Niña climate pattern — marked by cooler-than-average ocean water in the central Pacific Ocean — is one of the main drivers of weather in the U.S. and around the world, especially during the late fall, winter and early spring.

An official "La Niña watch" was issued last week by the prediction center, which means the pattern is likely to form within the next few months. If La Niña materializes, forecasters say it should be weak and potentially short-lived

“This climate outlook provides the most likely outcome for the upcoming winter season, but it also provides the public with a good reminder that winter is just up ahead and it’s a good time to prepare for typical winter hazards, such as extreme cold and snowstorms,” said Mike Halpert, deputy director of the Climate Prediction Center, in a statement.

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