NBC Chicago meteorologist Kevin Jeanes explains that after the warmest September in 64 years, Chicagoans might be in for a colder and wetter winter.
The National Oceanic and Atmospheric Administration has released its winter weather outlook for 2024-25, and Chicago-area residents will likely need to get boots and shovels ready.
That’s because the dominant weather pattern across the Great Lakes will likely be enhanced by a “slowly developing” La Niña event in the Pacific Ocean, according to NOAA officials.
That would ultimately result in a “wetter than normal” winter in the Great Lakes, especially in parts of Wisconsin, Illinois and Indiana.
That La Niña pattern is expected to grow stronger during meteorological winter, which runs from December 1 to February 28, and will likely steer the prevailing Jetstream further north, causing more storm systems to hit the Chicago area.
The big question will be whether or not temperatures will cause that precipitation to fall in the form of rain or snow. At this point, NOAA says that there are “equal chances” of above or below average temperatures, which can of course have a significant impact on whether it’s rain or snow that falls in the region.
According to the NOAA, they’ve implemented a series of upgrades to forecasting tools, including an experimental model called the “Probabilistic Winter Storm Severity Index.” That data was used to help with this year's projections after it was first implemented in late 2023, according to officials.
According to the University of Illinois, stronger La Niña patterns can produce winters that are typically “warmer and wetter than average,” with more snow and winter storms during those seasons. A La Niña also typically leads to cooler springs if the pattern persists.
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In a La Niña event, trade winds are stronger than usual, and they push warm water away from the Americas and toward Asia. This allows a process known as “upwelling,” which brings cold water to the ocean’s surface.
Those cold waters then cause the Polar Jetstream further north, leading to drought in the southern United States and more precipitation in the Midwest and in the Pacific Northwest.
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According to the latest updates from the Climate Prediction Center, La Niña is favored to emerge between the months of September and November, and is expected to persist at least through the winter months.
