*Great Lakes Ice Cover and Lake Effect Snow*

*Ice Covered Great Lakes and Lake Effect* This late in the winter season, we tend to see a lot of ice on the Great Lakes. Lake Erie is the one Great Lake that freezes over more than not. Lake Michigan and Lake Superior get plenty of ice to form near the shores and in the Straits Region (Lake Michigan) and around Whitefish Bay (Lake Superior). Lake Huron tends to see a lot of ice around Saginaw Bay stretching into Lake Huron as well as around the Straits Region. Because of their size, Superior, Michigan and Huron rarely freeze over. The question we get a lot is, “How come when the Great Lakes are covered with ice, we still get Lake Effect Snow Showers?” Of course, the moisture from the “warmer” Great Lakes is highly needed to get the heavy lake snows to form. But the ice coverage prevents truly heavy bands to get going. Other factors go into forming lake effect. (See my first blog posting on Dec. 14, 2010 for more specifics). So while the “moisture” from the Great Lakes is reduced this late in the season, there must be something that squeezes out the lake effect. The key is “Orographic Lifting”. This occurs when the wind comes over the flat, nearly frictionless (somewhat ice covered) Great Lakes and then plows into the shore and over the land. This creates friction as well as lift when it hits the land and elevation change. When air is lifted, you get clouds and eventually lake effect snow showers. Not only do you have the change in elevation and the friction, but with the very cold air aloft going over the relatively warmer surface, this will produce the clouds and perhaps some minor lake effect. Other factors (such as energy aloft, wind speed and direction, etc.) also contribute to lake effect even with ice on the Great Lakes. -Meteorologist Jim Lehocky