FZUS81 KCLE 061747 ICEGL Great Lakes Freeze-up Outlook National Weather Service Cleveland OH 1239 PM EST Wed Mar 6 2024 ...Maximum Ice Coverage for the Season Well Below Average at 17.68 Percent... The El Nino of 2023-2024 lived up to its billing and then some for the Great Lakes region that was characteristic of much less ice coverage than normal on the whole across all five of the lakes. This was the strongest El Nino since 2015-2016, and the Climate Prediction Center had indicated strong signals for above average temperatures, increasing in confidence further north towards the US - Canada border going into the fall of 2023. The most compelling data, other than the figures on the ice coverage itself, was perhaps the cumulative freezing degree days. As of March 5, 2024, freezing degree days were only a fraction of their normal values which was the story all winter, with all locations well below half and most of the southern sites current balance at zero. Outside of one sustained period of cold for around 2 weeks in the middle of January, cold airmasses that favored ice growth were consistently being replaced by airmasses that routinely oscillated between below freezing at night and above freezing during the day. Ice growth was just not able to get any traction, other than the most favored spots across the Great Lakes. But even those favored locations, such as the St Marys River, Straits of Mackinac, Green Bay, and Saginaw Bay showed significant signs of ice decay through February and into the first part of March. FREEZING DEGREE DAY ACCUMULATIONS AT SELECTED STATIONS COMPARED TO NORMAL CALCULATED ON Tue Mar 5: LOCATION DATE NORMAL CURRENT ---------------------------------------- DULUTH, MN MAR 4 1716 715 MARQUETTE, MI MAR 4 1492 630 SAU_S_MAR, MI MAR 4 1204 410 GREENBAY, WI MAR 4 989 145 MILWAUKEE, WI MAR 4 469 0 CHICAGO, IL MAR 4 350 0 MUSKEGON, MI MAR 4 321 0 ALPENA, MI MAR 4 893 185 DETROIT, MI MAR 4 349 0 TOLEDO, OH MAR 4 203 0 CLEVELAND, OH MAR 4 101 0 BUFFALO, NY MAR 4 427 0 Ice coverage peaked at 17.68 percent on January 22, 2024, approximately one month earlier than the annual normal for peak ice. This ice coverage maximum in January has only occurred two other times, in January of 2012 and January of 1999. This peak is far lower than the average annual maximum coverage of 53 percent. Current ice concentrations sit at less than 3 percent, with ice drifting around primarily on the western side of the Straits of Mackinac and the deterioration process continuing despite some overnights still below freezing. Sun angles increasing with the change in seasons as we approach spring will also help to inhibit any further significant ice formation as heating of the water under the ice can assist in the decay process despite any below freezing temperatures. When ice exists extensively in the rivers, flushing of the ice normally begins the first week of March. Areas of open water already exist and are continuing to expand in the St Marys River. The Straits of Mackinac and the St Marys River usually see their last ice in late April. With the warmer winter this season, the amount of significant ice remaining is low and is expected to be gone before this time frame. Perhaps using El Nino itself does not describe fully the unusually mild conditions that have been experienced in January and February of 2024. Northern Great Lakes climate sites, on average, were 4 to 6 degrees above normal for the month of January, and 2 to 4 degrees above normal across the southern Great Lakes climate sites. This was likely held in check somewhat by, again, that middle 10 day to 2 week period dominated by the polar vortex where we had our only really significant sustained cold/below freezing airmass in place for all of the Great Lakes for the season, yet the month of January still ended up well above normal. And yet, this paled in comparison to February 2024. The climate sites for the northern Great Lakes were anywhere from 9 to 12 degrees above normal for the month, with the southern Great Lakes slightly less dramatic, yet still well above normal at 7 to 10 degrees for the month. The North Atlantic Oscillation was in the positive phase for the bulk of the winter, with the exception of mid January, a characteristic of milder conditions for the eastern US. The result was the early ice coverage peak we saw and low percentage of coverage for the entire season. Satellite derived surface water temperatures show Lake Superior primarily showing mid to upper 30s, but still slightly colder in Whitefish Bay at just a couple of degrees above freezing. Lake Michigan sits near 40 degrees for much of the open waters except for the areas west of the Straits of Mackinac where water temperatures remain in the mid 30s at the surface. The same can be said for northern Lake Huron east of the Straits, but further south, upper 30s dominate all the way down to the St. Clair River. Lake Erie is also in the upper 30s across the western and central basin, and low to mid 30s for the eastern basin. Looking ahead through the rest of March, the Climate Prediction Center continues to push warmer than normal conditions for the Great Lakes, again, increasing in confidence towards the US - Canadian border. There will likely be a transition to a neutral phase of El Nino in late Spring, and then possibly back to La Nina for the next ice season coming up at the end of 2024. While colder airmass intrusion into the Great Lakes region is certainly possible even into April, additional significant ice formation is not expected. This will be the last ice product issued for the 2023-2024 ice season. Special thanks to the US National Ice Center for their coordination this season. The next freeze-up outlook for the upcoming 2024-2025 winter season will be issued during the first week of November and will be issued every two weeks until ice begins to develop on the Great Lakes. $$ Marsalek