This article was inspired by my colleague Leslie Morrow at the University of Georgia. She tagged me in a Facebook post asking about El Niño and its potential effects on snow likelihood in Georgia this winter. Leslie loooooooooves snow, and it is a fair question to ask. Let’s dive deeper into the discussion.
El Niño Refresher
I’ll start with a quick refresher on El Niño. The National Oceanic and Atmospheric Administration confirms that an intensifying El Niño is present. “Equatorial sea surface temperatures (SSTs) are above average across the central and eastern Pacific Ocean,” according to the NOAA update issued on August 3. “El Niño will strengthen through the end of the year, with a 97% chance it will persist through early spring 2027,” the update went on to say. NOAA’s Climate Prediction Center, which you should trust more than almanacs and groundhogs, puts the chances of a very strong El Niño in the Fall at 81%.
What happens in the ocean doesn’t stay in the ocean when it comes to El Niño. It affects weather patterns around the world. “The warmer waters cause the Pacific jet stream to move south of its neutral position. With this shift, areas in the northern U.S. and Canada are dryer and warmer than usual,” wrote experts at NOAA. Such conditions are likely factors in the extremely dry conditions and Canadian wildfires in recent months. “But in the U.S. Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding,” NOAA’s website continued. Because of increased wind shear environments, Atlantic hurricane activity is often reduced as well.
What About Snow?
Ok, Dr. Shepherd, enough of the weather lessons, I want to know about the snow. Okay, okay, I hear you. To have that discussion, I need to circle back to the jet stream. Meteorologists like me watch the jet stream, a strong concentration of winds in the upper atmosphere, because it is a dividing line between cooler and warmer temperatures. It’s actually more complicated than that, but trust me, you don’t want the all of the physics, thermodynamics, and fluid dynamics details.
Since the jet stream tends to be displaced southward during El Niño, colder air can dig further south too. In a 2023 NOAA blog, my colleagues Michelle L’Heureux and Brian Brettschneider explored who the “snow winners” are during El Niño. The map below compares snowfall during moderate-to-strong El Niño winters, which is expected this year. The takeaways are clear:
- Reduced snowfall (brown) in much of the northern tier of the U.S. and Canada.
- Increased snowfall (blue) in the southwestern U.S., southern/central Plains and parts of the Southeast.
- A swath of increased snowfall in the southern Appalachians
- Noticeable snowfall declines around the Great Lakes, Northeast, and upper Northwest.
To the snow lovers in the South, this certainly should bring hope for you. However, you know a “but” is coming. Actually, there are a couple of “buts.” We live in the South, so there is a limit to just how cold we tend to get. In some parts of the South, wintry weather often means freezing rain or sleet. Those of us who live in the Atlanta area are quite familiar with the “where’s the rain/freezing rain/snow line?” question. L’Heureux and Brettschneider issued another caution also. “Relying on the average is a bit dangerous because a few heavy snowfall winters can give the impression that most winters are above average,” they warned.
Climate change is also a factor. “Unsurprisingly, because of climate change, over most of the contiguous United States we have trended toward less snowy winters,” they continued. It is important to remember that we will have winter as climate warms. Seasons are caused by the Earth’s tilt and orbit around the Sun. During winter, it can still be cold or actually even snow, so please don’t ask a scientist, “What happened to global warming?” because it is cold in February. However, it is undeniable that snowfall has trended downward in many parts of the country in recent decades. In fact, a study by Climate Central found that 64% of U.S. locations are less snowy than they were in the early 1970s.
As a scientist who has studied the atmosphere for over 30 years, there are so many challengings aspects to answering questions about snow potential and El Niño. We certainly know that southern winters may skew colder, but that is not the “smoking gun” for snow. Each El Niño has a different personality, and many other factors come into play.