Updated October 25th. The Army Corps of Engineers – Detroit District’s reports as of October 2020 for Great Lakes Water Levels and Great Lakes Water Level History.
The October 23rd forecasted levels for Lakes Superior, St. Clair, and Erie are 1, 5, and 4 inches, respectively, below what they were one month ago, while Lakes Michigan-Huron and Ontario are both 3 inches below their levels of one month ago. In comparison to last year, the projected Friday water levels of Lakes Superior, Michigan-Huron, and Ontario are 6, 2, and 12 inches, respectively, below their levels from one year ago, while Lakes St. Clair and Erie are both 1 inch above their levels from one year ago.
All lakes remain above their long-term monthly average October levels but below their record high October average levels. Water levels are forecast to continue their seasonal decline in all lakes over the next month. By November 23rd, water levels are projected to decline by 2 to 3 inches on Lakes Superior, Michigan-Huron, and Ontario and to decline by 4 to 5 inches on Lakes St. Clair and Erie.
Lake Superior’s outflow through the St. Mary’s River and Lake Michigan-Huron’s outflow through the St. Clair River are projected to be above average in October. Also, Lake St. Clair’s outflow into the Detroit River is predicted to be above average for October. Lake Erie’s outflow into the Niagara River is predicted to be above average for October. Moreover, Lake Ontario’s outflow into the St. Lawrence River is predicted to be above average this October.
Long Term Great Lakes Water Level Estimates
Preliminary estimates indicate the Great Lakes basin’s precipitation, and each lake basin was below average in September. As a result of below-average precipitation, water supplies to all the lakes, except Lake Superior, were below average. This was especially true for Lakes Erie and Ontario, which experienced arid conditions. Despite below-average water supplies this month for most lakes, water levels remain high and so outflows remained above average. Preliminary estimates indicate that outflows through the St. Clair River and Detroit River were above their September record-high outflows.
Water levels for all the Great Lakes declined from August to September. Lake Superior declined about 1 inch, while Lakes Michigan-Huron, St. Clair, and Erie declined by 3 to 4 inches from August to September. Lake Ontario also dropped 8 inches in the last month. In September, the monthly mean level for Lake St. Clair was a new record high, which surpassed its previous record high from last year by 1 inch. The current 6-month forecast predicts all lakes to continue their seasonal water level declines throughout the fall.
Current Great Lakes Water Level Projections
Near or above the record high water levels continue on all lakes, except Lake Ontario. Lake St. Clair was the only lake to set a record high monthly mean level in September. The current Great Lakes water level forecast indicates water levels to be slightly below record-high levels over the next 6 months but still above average. Water levels follow a seasonal cycle where water levels rise in the spring due to increased precipitation and enhanced runoff from snowmelt. In the summer, water levels typically reach their peak level. In the fall, the lakes generally decline due to an increase in evaporation as temperatures decline, and cold air moves over the relatively warm lake waters. We refer to the combined effect of precipitation over the lake, evaporation from the lake, and runoff to the lake as Net Basin Supply (NBS).
This past August, La Niña conditions developed in the equatorial Pacific Ocean. This means that the sea surface temperatures in the eastern and central equatorial Pacific Ocean are cooler than normal.
When this occurs, there can be impacts on the weather experienced in the Great Lakes region, especially in the winter. The current forecast issued by the Climate Prediction Center expects that La Niña will last through the winter. Figure 1 depicts the weather conditions that typically occur then a La Niña is present in the winter. For the Great Lakes basin, southern portions of the basin could experience wetter than normal conditions, and colder air could push further south into the region.
2020 Yearly Great Lakes Water Level History
Lake Michigan-Huron has set a record high monthly mean level for 9 consecutive months. Also, the August 2020 level was 4 inches above its August 2019 level and 33 inches above its August Long Term Average level.
Weather Outlook for the Rest of 2020
The recent 1-month climate forecast updated by the Climate Prediction Center shows a likelihood of above-normal temperatures for October. The forecast for precipitation in October indicates the likelihood of below-normal precipitation for the entire Great Lakes basin. The seasonal three-month outlooks for temperatures in the late fall and early winter (October, November, December) indicate a likelihood of above-normal temperatures throughout the Great Lakes basin. The seasonal three-month outlook for precipitation generally shows equal chances of above, below, or normal precipitation.
Daily Great Lakes Water Level History
The report below is a view of long-term, basin-scale hydrological data for the Laurentian Great Lakes. Water levels are continuously observed by U.S. and Canadian federal agencies in the region through binational cooperation. NOAA-GLERL relies on this water level data to conduct research on the regional water budget components and improve predictive models.
NOAA’s Center operates water level monitoring stations for Operational Oceanographic Products and Services and the Department of Fisheries and Oceans’ Canadian Hydrographic Service. The U.S. Army Corps of Engineers (Detroit, Chicago, Buffalo) and Environment and Climate Change Canada play crucial roles in research, coordination of data, and operational seasonal water level forecasts for the basin.
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