Wisconsin winter forecast: El Niño, what it means for you
MILWAUKEE - We are already starting to feel the fall chill. Winter isn’t here yet, but El Niño is – and it is forecast to get stronger over the next few months.
Winter in Wisconsin always features some cold and some snow. But how much snow and cold is determined by many different factors – from small scale factors, like winds off Lake Michigan, to large scale factors, like El Niño. Both will likely play a role this winter.
The winter of 2023-2024 is forecast to be a strong El Niño year. But what does that mean? First, we have to define what El Niño is.
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El Niño defined
El Niño is the warming of the ocean water off of the equatorial Pacific. When these waters warm up, it changes the jet stream structure, which drives our weather patterns here in the U.S. Instead of seeing the typical strong easterly trade winds in this area, there is a weakening of these winds, allowing warm waters to spread east to the coast of Peru.
In fact, El Niños have adversely impacted fishing in these areas for centuries. As the eastern Pacific waters warm up, it strengthens what is called a "Hadley Cell" – which is the connection between the ocean and the atmosphere. The stronger the El Niño, the stronger and farther south the Pacific jet stream or storm track moves. This means active weather across the southern tier of states.
The question for us this winter is where this northern "polar" jet stream ends up. If it stays north, we stay warmer. Also, given the precipitation down south, that could serve to cut off moisture for storms around here and keep us drier. If El Niño is the dominant and only influence of our winter, it would typically mean a warmer and drier than average winter.
Winter ahead
What does all of this mean for our winter ahead? The official winter forecast is in line with a strong El Niño winter pattern in the Upper Midwest: drier and warmer than average.
Wetter than average weather is expected across the deep south, lining up with the strong Pacific jet stream.
It’s important to remember El Niño is a global-scale phenomenon. More specific factors, like moisture from Lake Michigan, and even more importantly, the track of low pressure systems, will often dictate whether we see snow or if it stays 50 miles to our north or south.
The bottom line
El Niño could shift those low pressure systems. But storm placement will also dictate whether we see lake effect snow or lake enhanced snow, which could be a factor in how much snow we see this winter. While we are expecting a warmer and drier winter than average, rest assured this winter will still have cold snaps and occasional snow.