La Niña Likely to Influence a Mixed Winter Weather Outlook Across U.S., With Warmer Than Normal Conditions Predicted for Most Regions

The transition from a scorching summer into fall provides a reprieve for much of the United States, but meteorologists are already contemplating the arrival of winter and the potential reappearance of a significant atmospheric phenomenon: La Niña.

The National Oceanic and Atmospheric Administration (NOAA) has predicted that La Niña could emerge as early as this fall, with odds of approximately 53% from September through November. By year-end, the chances increase slightly to 58%. These forecasts have prompted NOAA to issue a La Niña watch.

Upon its arrival, La Niña is expected to persist throughout winter and exert an influence on temperature and precipitation patterns across the country before dissipating in early spring.

To clarify, La Niña refers to a natural climate pattern characterized by cooler-than-average water temperatures in the equatorial Pacific that affect upper atmosphere patterns globally. Both El Niño and La Niña are closely monitored due to their predictable impact on weather patterns, particularly during winter in the Northern Hemisphere.

As a weaker La Niña is forecasted, its influence may not be as pronounced, which could lead to mixed weather patterns in the coming months.

The emergence of La Niña conditions should occur gradually throughout fall, with NOAA potentially declaring its official arrival at the end of the season or around the start of winter.

Unlike last winter, when La Niña was tardy and did not linger, this upcoming La Niña is expected to arrive on time for winter and persist for much of the season.

While La Niña provides a forecasting blueprint for temperature and precipitation trends during winter, its influence can be unpredictable, especially when it’s weaker. Other atmospheric factors could come into play, potentially altering the expected weather patterns.

La Niña primarily affects the jet stream, which is a river of air that storms follow. During a La Niña winter, the jet stream often shifts northward, drawing stormy weather towards the northern United States.

The Climate Prediction Center’s (CPC) forecast for meteorological winter (December through February) shows the influence of La Niña, with many southern states anticipated to experience drier conditions and pockets of the northern US expecting increased precipitation compared to normal levels.

However, more precipitation does not guarantee snowfall. Temperatures need to be cold enough both above and at ground level for snow to accumulate, which might not occur this winter.

Typically, La Niña winters favor warmer temperatures in the South and cooler conditions in northwest and north-central states. This year, however, warmer-than-normal temperatures are predicted across a broad swath of the country, including the South, Southwest, parts of the Rockies, and most of the Eastern Seaboard, indicating that La Niña is not the sole determinant for CPC’s forecasts.

Weaker La Niña events tend to promote more snow in the Northeast, but the above-average temperature forecast might hinder dreams of a winter wonderland. Only a small portion of the Pacific Northwest is projected to experience cooler temperatures this winter, with the rest of the country seeing a mix of warmer, cooler, or near-normal conditions.

Last winter was not exceptionally warm compared to recent records, but it was still warmer than 80% of all winter seasons since the late 1800s. As global temperatures rise due to fossil fuel emissions, the concept of a typical winter is becoming increasingly distorted, with winter being the fastest-warming season for nearly 75% of the US. Snowfall is also decreasing around the world as the climate changes.