Image Courtesy: Michael Karow

Cooler In the Lake

By Sam Dunaiski @yourmetsam March 29, 2016 10:04 am CDT

The Great Lakes contain roughly 10% of the world's surface fresh water. They can often create their own weather features across the Midwest and the Northeast. In the winter months, the lakes can affect the surrounding areas both in terms of temperature and snowfall. The term "lake-effect snow" is very well known, but the Great Lakes can also help to keep the temperatures of the surrounding landmass warmer as well. Of course, that is only if the lakes are warmer than the surrounding land. As we found out last year, even for the world's biggest freshwater lake, this is not always the case.


Surface Temps

Current Water Temps via Great Lakes Environmental Research Laboratory


Last winter, Lake Superior almost completely froze over, something it hadn't done since 1996. This fact becomes even more impressive considering the temperature of the lake last fall heading into winter. Last October, the average surface temperature of the lake was 52.5° F, putting it above the average monthly temperature of 50°. The temperatures fell off considerably through last October, starting at 56.05° and falling to 46.04° by the end of the month. The lake typically only drops by about 7 degrees during October, one of the sharpest declines of any part of the year.


Average Surface Water Temps over the last 6 years via Great Lakes CoastWatch


As you can see from the graph above, last year (blue line) was one of the more mild Octobers in recent history.  In those years, only the winter of 2008-2009 saw more than 40% of the lake freeze over.


This year, the lake is already staring out rather chilly.  At the moment, the average surface temperature of Lake Superior sits at 45.9°, which is below the average of 46.7°. That temperature anomaly was closer to 4° (6° cooler than 2013) early this month, but a relatively warm end to October has lessened the typical fall tumble.

2014 Lake Surface Temps Compared to 30 Yr Average via Great Lakes CoastWatch


With lake surface temperatures being below average and far below last year's numbers, another harsh winter could spell another massive freeze this winter, and thus another chilly summer for 2015. Thankfully, the forecast this winter does look to keep the Midwest a bit warmer and drier. However, a warmer lake with open waters could also result in more lake-effect snows.


Sadly, at this point, we must play the waiting game.

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