NOAA releases winter weather forecast for Chicago area – NBC Chicago

The National Oceanic and Atmospheric Administration has released its winter weather outlook for 2024-25, and Chicago area residents will likely need to get their boots and shovels ready.

That's because the prevailing weather pattern in the Great Lakes is likely being reinforced by a “slow-developing” La Niña event in the Pacific Ocean, according to NOAA officials.

This would ultimately lead to a “wetter than normal” winter in the Great Lakes, particularly parts of Wisconsin, Illinois and Indiana.

This La Niña pattern is expected to strengthen during the meteorological winter, which runs from December 1 to February 28, and is likely to direct the prevailing jet stream further north, resulting in more storm systems hitting the area Meet Chicago.

The big question will be whether temperatures will cause precipitation to fall in the form of rain or snow. At this point, NOAA says the chances of above- or below-average temperatures are “equal,” which of course can have a significant impact on whether the region sees rain or snow.

According to NOAA, they have implemented a number of upgrades to forecast tools, including an experimental model called the Probabilistic Winter Storm Severity Index. That data was used to support this year's forecasts after they were first implemented in late 2023, officials said.

According to the University of Illinois, stronger La Niña patterns can result in winters that are typically “warmer and wetter than average,” with more snow and winter storms during these seasons. A La Niña also typically leads to cooler springs if the pattern continues.

During a La Niña event, trade winds are stronger than usual, pushing warm water away from the Americas and into Asia. This enables a process known as “upwelling,” which brings cold water to the ocean’s surface.

This cold water then causes the Polar Jet Stream further north, leading to drought in the southern United States and increased rainfall in the Midwest and Pacific Northwest.

According to the latest updates from the Climate Prediction Center, La Niña tends to occur between September and November and is expected to last at least into the winter months.