####018006786#### FZUS81 KCLE 052128 ICEGL Great Lakes Freeze-up Outlook National Weather Service Cleveland OH 426 PM EST Tue Dec 5 2023 ...Great Lakes Ice Season for 2023-2024 Still Expected to Be Average to Slightly Below-Average Ice Coverage... The El Nino Advisory continues with sea surface temperature anomalies over the equatorial Pacific increasing over the past month. Confidence remains high that El Nino persists through the winter season and well into the spring. The southern storm track should be a more dominant feature over the winter across the southern tier of states while the US-Canadian border should trend milder than normal overall without long residence time Arctic outbreaks. The Arctic Oscillation, which had trended negative for a short period of time looks to transition back to neutral by the middle of December. Meanwhile, the North Atlantic Oscillation and the Pacific North American pattern continue with their neutral tendency. The middle of November saw milder than normal conditions for the bulk of the Great Lakes, with higher departures from normal over the northern portion of the region. As we headed into the end of November, some advertised colder air made its way into the Great Lakes and for a period of 5 to 6 days in the latter part of the month, temperatures were below normal. This was a result of a broad upper level low pressure system over the region with reinforcing trough axes swinging through that kept the colder airmass in place for a few days. Temperatures generally ranged from 5 to 15 degrees below normal during this time. As expected as we get deeper into fall, there was continued heat loss from the Great Lakes. The active weather pattern at the end of the month and colder air also contributed to heat removal from the lakes. The shorter days and lack of insolation was also a contributor as well. Although the first ice of the season appeared in one of the bays in northern Lake Superior along the Ontario shore east of Thunder Bay, only now seeing the first of the open water temperatures in the 30s for the season. With buoys being pulled for the winter, satellite derived water temperatures are showing open waters of Lake Superior including Whitefish Bay in the upper 30s to lower 40s. The coastal areas of Duluth Harbor are beginning to drop into the upper 30s, as are most of the shallower and smaller area harbors across all lakes, including but not limited to Green Bay, Little Bay de Noc, and Big Bay de Noc. Farther south in the shallow western basin of Lake Erie, surface temperatures are primarily in the upper 30s as well. Meanwhile, Saginaw Bay is mid to upper 30s, and best estimates along the St. Mary's River have it in the mid 30s as well. The open waters of Lake Michigan and Lake Huron remain the lower 40s over the northern parts of each lake, including the Straits of Mackinac, while the southern portions of these lakes are still in the mid to upper 40s. The central and eastern basin of Lake Erie also resides in the mid 40s, with a small area of upper 40s just east of Erie, PA. Over the next few days, the area will cycle through below freezing temperatures at night, and back above freezing during the daytime hours for the majority of the region. Moving into the coming weekend, the Great Lakes will be in line for a couple of upper level troughs with below freezing air for the northern lakes resulting in more efficient heat loss from those portions of the lakes including all of Lake Superior. Across the southern portions, a different story as the surface low pressure systems will bring periods of warm air advection that will not reach their northern counterparts of the lakes. This will result in a shorter period of residence time of any below freezing air for southern Lake Michigan, southern Lake Huron, and Lake Erie that comes early next week. The nature of the systems moving through will be characteristic of windier conditions which will support continued upwelling/downwelling involving the surface water, so while heat removal, especially in the northern Great Lakes, will be fairly efficient, temperature drops may still be on the slow and steady side. Heading through the end of next week, milder than normal conditions are expected to return with the Climate Prediction Center 8-14 day outlook again trending above normal for temperatures, also seen in the long range ensembles. The latest 3-4 week outlook and one month outlook also continue the same theme with above normal temperatures expected. It should be noted that this does not mean there will not be any below normal temperatures through the month because of the milder signal in the outlooks, but what it will likely translate to is slow/delayed ice growth as we get into astronomical winter towards the end of the month. Ultimately, while some ice formation is possible in the shallower bays and immediate coastal areas of the northern Great Lakes during the upcoming cold stretch, significant ice formation is not expected in the next two weeks. Another freeze-up outlook will be issued with the expected slow ice formation. Ice formation is determined by two factors: The amount of heat stored in the water from the summer and how fast that heat can be removed by arctic outbreaks of Polar air and high winds. Long range outlooks do not consider the "storminess" factor which can significantly alter the lakes thermal structure over short periods of time. Freezing degree days are starting to accumulate across the northern part of the Great Lakes. Otherwise, generally only a few freezing degree days have been reported elsewhere on the lakes due to the periodic milder periods the area has experienced. FREEZING DEGREE DAY ACCUMULATIONS AT SELECTED STATIONS COMPARED TO NORMAL CALCULATED ON Sat Dec 2: LOCATION DATE NORMAL CURRENT ---------------------------------------- DULUTH, MN DEC 1 102 103 MARQUETTE, MI DEC 1 75 75 SAU_S_MAR, MI DEC 1 14 39 GREENBAY, WI DEC 1 8 52 MILWAUKEE, WI DEC 1 0 2 CHICAGO, IL DEC 1 0 6 MUSKEGON, MI DEC 1 0 0 ALPENA, MI DEC 1 1 27 DETROIT, MI DEC 1 0 1 TOLEDO, OH DEC 1 0 0 CLEVELAND, OH DEC 1 0 0 BUFFALO, NY DEC 1 0 0 THE NEXT FREEZE UP OUTLOOK WILL BE ISSUED IN APPROXIMATELY TWO WEEKS. $$ Marsalek