Great lakes ice coverage remains well below average. Here's how that could affect the weather

Warm weather has resulted in record-low ice levels across the Great Lakes this winter, which could lead to increased lake-effect snow and flooding concerns for cities and towns along the shorelines.

The warmer weather in the region resulted in dwindling ice starting in January, with several cities reporting their warmest start to the year on record, according to NOAA Regional Climate Centers.

Ice coverage was below the historical average across the Great Lakes as the calendar turned to February, starting the month with around 12 percent of the lakes covered in ice. Extreme cold brought on by a shift in the polar vortex early in the month lowered temperatures significantly, which helped bring the amount of ice on the Great Lakes to 21 percent on Feb. 4.

The dramatic changes in temperature rapidly changed ice conditions in Lake Erie. On Jan. 30, Lake Erie was covered by just 0.32 percent of ice, but the Feb. 5 cold snap quickly sent ice coverage to 40 percent. Just one week later, ice cover had plummeted to 0.60 percent as warm weather returned.

This MODIS satellite image from Feb. 12, 2023, shows below-average ice cover for this time of year on the Great Lakes. Credit: NOAA GLERL / NOAA Great Lakes CoastWatch Node.

Ice was on the decline across the Great Lakes as a whole from Feb. 5 to Feb. 13 due to above-average warmth. Within a couple of weeks of the cold moving out of the area, ice coverage dropped to just 7 percent on Feb. 13, which is a significant 30 percent below the average and a record low for the date.

As of Feb. 19, cities such as Milwaukee and Muskegon, Michigan, have recorded their warmest start to the year ever, with temperatures averaging 7 degrees warmer than the historical average in both cities. Similarly, cities along the border of the lakes, such as Alpena, Michigan, and Cleveland, Ohio, are observing their second warmest year on record so far.

"If you look at the past month, [for] most of the bigger cities off lakes Erie and Michigan and Ontario, the nighttime lows have been at or above the historical averages," said AccuWeather Long-Range Forecaster Paul Pastelok.

The largely ice-free lakes, along with other weather factors, have helped the daytime high temperatures stay above the historical average for cities along the lakes.

Ice forms on pilings in Lake Michigan near Fullerton Beach, Friday, Feb. 3, 2023, in Chicago. Temperatures hovered in the single digits for most of the day. (AP Photo/Erin Hooley)

The abnormally warm weather extended beyond the Great Lakes as January became the sixth-warmest on record for the entire United States, which recorded an average temperature of 35.2 degrees -- about 5 degrees above the historical average.

"Any chilly air masses following cold fronts are brief and modify quicker with open lakes compared to ice-covered lakes," said Pastelok.

Great Lakes ice coverage is important for protecting the shorelines because, without the ice, high waves can lead to severe flooding on the coast, according to NOAA. Low ice coverage can lead to an extended lake-effect snow season, which already brought a powerful storm in December that dumped over 4 feet of snow in Buffalo and resulted in at least 27 fatalities.

"Late-season lake-effect is a concern in the late winter or early spring season where cold air is forecast. With the polar vortex displaced and an increase in blocking expected over the northern Atlantic in late February and March, that chance does exist this year," explained Pastelok.

As of Feb. 19, ice coverage on the lakes has increased slightly to 9.5 percent. The highest ice coverage recorded on the lakes this season was about 22 percent.

A person takes a picture of the waves crashing onto the shore as ice forms on Oak Street Beach Friday, Feb. 3, 2023, in downtown Chicago. (AP Photo/Kiichiro Sato)

Seasonal ice coverage on the Great Lakes has been on a downward trend over the years, according to NOAA research. During the winter season, average ice cover on the lakes has declined by about 70 percent between 1973 to 2017, according to an analysis led by Jia Wang, an ice climatologist at NOAA's GLERL.

With colder periods expected in the coming weeks, ice concentration may build into early March.

"There still may be some milder periods in March before more chill arrives again later in the month," explained Pastelok.

As the weather turns warmer in mid- to late spring, the lake-effect precipitation may transition from snow to rain. The open waters caused by the early ice melt will increase evaporation earlier than usual, which can lead to more frequent or intense rain events. Most of the eastern Great Lakes are forecast to have above-average precipitation this spring, according to Pastelok.

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