Great Lakes ice - what to expect

The Great Lakes are one of the main snow machines of the Snowbelt in the U.S. As the winter solstice draws near, the waters on the Great Lakes will be freezing soon, but how much they freeze depends on the climate and weather patterns.

The Snowbelt, stretching from the northeastern tip of Minnesota through northern Illinois and into interior New York, is used to receiving feet of snow thanks to the Great Lakes. Residents in these areas may be wondering when the lakes will freeze for the winter, shutting off one of the main early-season snow machines.

How fast and how soon the Great Lakes freeze over depends on the status four main large-scale climate patterns used to forecast the Great Lakes ice coverage. These large-scale patterns can determine the average location of the jet stream – the planetary river of very fast winds that can influence where cold air pours into.

The jet stream can usher freezing or subfreezing temperatures across the Great Lakes. But this cold weather pattern is needed for several days to weeks for the water temperatures to begin decreasing.

Even if the outdoor temperature has been at the freezing mark or below it for some time, it still takes awhile for the water temperatures to come down and eventually freeze. Water retains heat much longer than air, and the Great Lakes, especially the deeper ones, can take a while for ice to begin to form.

Speaking of depth, this is why you see ice forming on the shorelines first since there is less water to have to cool. The deeper the water, the more water circulation there is. This keeps temperatures above freezing at this point.

One of the large-scale climate patterns observed to predict Great Lakes ice is the El Nino Southern Oscillation (ENSO). El Nino is the warm phase of this climate pattern and usually results in less ice cover, while La Nina is ENSO’s cold counterpart. This year, we’re in a La Nina phase.

This year’s La Nina phase could keep ice cover at a 50/50 chance. Research shows that stronger La Nina events show less ice growth while weak ones bring higher ice growth on the Great Lakes. The La Nina forecast is currently at a moderate strength. While we will see ice cover, how much depends on the positioning of that jet stream.

Records kept since 1973 have shown a pattern of maximum ice cover being observed in either February or March due to the mostly consistent cold-weather pattern the Great Lakes have by this time of year.

With that, the lake-effect snow machine has awhile before it could turn off! Keep an eye on your WeatherRadar to note when you could be seeing lake-effect snow and your TemperatureRadar to check when freezing temperatures will cover the Great Lakes region.