La Niña's weak link to winter snowfall
Weak La Niña conditions are now in place and are expected to persist throughout the winter. This could have some impact on snowfall amounts in parts of the United States this season.
What is La Niña? La Niña is a periodic cooling of water in the eastern and central Pacific Ocean near the equator. A La Niña is declared when sea surface temperatures are at least 0.9 degrees Fahrenheit (0.5 degrees Celsius) cooler than average and the atmosphere responds to this for at least three consecutive months.
It means “little girl” in Spanish and is the opposite of El Niño, which was discovered in the 17th century by fishermen who first spotted its warm waters off the Pacific coast of South America.
The sea surface temperature anomaly shows the strong La Niña event that occurred in November 2007, as indicated by the black arrow.
(NOAA/Climate.gov)
It's been here for a while: La Niña conditions are expected to continue into February, according to the National Oceanic and Atmospheric Administration's Climate Prediction Center.
Most computer model guidance suggests that La Niña is likely to be weak this time around.
Why it's important: While La Niña is not the only influence, its cooling effect on equatorial Pacific waters could affect weather patterns thousands of miles away, including near the United States
That means it could affect, among other things, the amount of snowfall this winter.
So let’s take a closer look at past weak La Niña winters to see if there are any clues to predicting what snow will look like this winter. We'll conclude with some important disclaimers.
General overview: The NOAA Climate Prediction Center examined snowfall during weaker (and stronger) La Niñas from 1950 to 2009 and found an interesting pattern.
That said, weak La Niñas typically produce above-average snowfall across much of the northern United States, from the northwest Cascades to the upper Midwest and New England.
Snowfall amounts are generally below average in the southern Rockies and parts of the Ohio Valley.
During weak La Niña conditions from 1950 to 2009, snowfall from October to April deviated from average in inches.
(National Oceanic and Atmospheric Administration)
Regional perspective: We also examined snowfall in several cities in each region during 12 weak La Niña winters since 1950 to see if we could identify a signal in the data.
northeast
The overall picture is that winter snowfall is relatively low along the Northeast Corridor of Interstate 95, especially in the mid-Atlantic states. For example, two of the 12 weak La Niña winters in Washington, D.C., had above-average snowfall
However, winter snowfall is heavier in the Eastern Great Lakes Snow Belt (Buffalo and Syracuse, New York) and in northern New England.
The dark blue bars show seasonal snowfall averages during 12 weak La Niña winters since 1950 for four cities in the northeastern United States. The light blue bars represent the long-term (spring 1950 to 2025) average seasonal snowfall for each city.
(Data: NOAA/NWS)
Midwest
The North-South divide is particularly evident when looking at the central region of the country.
Bismarck (North Dakota); Duluth, Minnesota; and Minneapolis-St. During weak La Niña seasons, Paul's average snowfall is at least 10 inches above average.
However, less snow fell in the central Plains, central Mississippi Valley, and Ohio Valley. For example, St. Louis received about one-third less snowfall during a weak La Niña winter (about 13 inches) than the long-term average (about 18.5 inches).
As mentioned above, with the exception of four Midwestern cities.
(Data: NOAA/NWS)
The west
We find that, with few exceptions, much of the West receives more snow during weak La Niña periods.
This is the case in Alaska, the Cascades, the Great Basin, the northern Rockies, and at least parts of the California Mountains.
The exceptions are the southern Rockies and areas as far north as Denver. Albuquerque, New Mexico, receives its least snow during the winter during weak La Niña conditions.
Same as above, except four cities in the west.
(Data: NOAA/NWS)
South
Think of the numbers you see below as reduced snow chances or fewer snowfall events in the South rather than focusing on the exact numbers since that area gets less snow than the rest of the country.
Overall, winters with weaker La Niña conditions are less likely to snow. From the Texas Panhandle to Virginia, we noticed this was a consistent signal.
Even normally snowy Roanoke, Virginia, saw a 36% decrease in seasonal snowfall during the weak La Niña winter.
Same as above, except the four southern cities.
(Data: NOAA/NWS)
asterisk*: The value we calculated above is the average of 12 weak La Niña seasons. Averages can, and often do, mask significant seasonal variation.
For example, while Philadelphia mathematically shows a good, less snowy signal when all 12 weak La Niña seasons are blended together, snowfall amounts in those seasons range from nearly 30 inches in 2017-18 to just 0.3 inches in 2022-23.
The reason for this change: The evolution of winter weather patterns is driven by many factors, not just La Niña.
Additionally, a weaker La Niña may have less of an impact on weather patterns than a stronger La Niña.
Another factor that occasionally affects winter patterns may be sudden, sharp warming events high in the atmosphere called sudden stratospheric warming.
These disrupt and weaken the polar vortex, which then, regardless of La Niña conditions, creates a blocking pattern that brings colder air into the United States during the winter weeks ahead.
Finally, there is climate change.
Winter is the fastest-warming season in much of the United States over the past few decades, according to a Climate Central study. Cold outbreaks are shortening in duration and less cold. Climate Central found that winter temperatures were more than two weeks warmer than average in parts of the Midwest and Northeast compared with 1970.
Temperature changes from December to February from 1970 to February 2024.
(Climate Central)
All of these factors make winter seasonal forecasts challenging, including this winter.
Jonathan Erdman is a senior meteorologist for Weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite topics. contact him X (formerly Twitter), Number of threads, Facebook and blue sky.