A weak La Niña phenomenon is expected to influence winter weather patterns in the United States this season. This cooling event in the Pacific Ocean could significantly affect snowfall levels across various regions.
Understanding La Niña
La Niña refers to the periodic cooling of water in the eastern and central Pacific Ocean near the equator. It is declared when sea-surface temperatures drop by at least 0.9 degrees Fahrenheit (0.5 degrees Celsius) for a minimum of three consecutive months. This phenomenon serves as the oceanic counterpart to El Niño, which typically brings warmer water to the same region.
Expectations for Winter 2023-2024
According to NOAA’s Climate Prediction Center, the current weak La Niña is anticipated to persist through February. Computer models suggest that this instance is likely to be mild. The impact of La Niña extends beyond the Pacific, affecting weather patterns across the U.S., particularly snowfall.
Historical Snowfall Patterns During Weak La Niña
Analysis of snowfall from 1950 to 2009 indicates trends influenced by weak La Niña events. Key findings include:
- Regions in the northern United States typically receive above-average snowfall.
- The southern Rockies and parts of the Ohio Valley generally experience below-average snowfall during these events.
Regional Snowfall Forecast
Examining 12 weak La Niña winters provides further insights into snowfall patterns across various regions:
Northeast
The Northeast, particularly the Interstate 95 corridor, often sees less snow. However, areas in northern New England and the eastern Great Lakes may still experience snowier winters. For instance, Washington, D.C., recorded only two out of twelve weak La Niña winters with above-average snow.
Midwest
In the Midwest, snowfall differentials are pronounced. Cities like Bismarck, North Dakota, and Duluth, Minnesota, tend to receive at least ten inches more snow than average during weak La Niña winters. In contrast, regions like St. Louis experience approximately a one-third reduction in snowfall.
West
The western U.S. typically sees increased snow levels during weak La Niña episodes, especially in areas such as Alaska and parts of California’s Sierra Nevada. However, southern Rockies, including Denver, may have reduced snowfall events.
South
Southern states are likely to witness fewer snow events overall. Cities from the Texas Panhandle to Virginia report a consistent decrease in snowfall during weak La Niña winters. For example, Roanoke, Virginia, recorded a 36% reduction in its average seasonal snowfall.
Forecast Challenges
While the historical data provides trends, variations exist from season to season. Factors such as sudden stratospheric warmings can disrupt normal weather patterns, complicating the impact of La Niña. Climate change also poses additional challenges, with winter temperatures increasing significantly over decades.
Overall, predicting snowfall amidst a weak La Niña presents complexities. Observers and meteorologists must consider a multitude of factors influencing winter weather patterns.
