To follow up on my earlier post, a very shallow very large inland lake is in danger of becoming this, with just a very mild shift in climate. 20 feet is very likely to be seasonal, with fast stretches of the lake bottom exposed on a yearly basis.
Large, deep waters that stay open into the winter months of a temperate region can lead to lake effect snow. Parts of Michigan's Upper Peninsula average close to 250 inches of snow per year, and the record one-season snowfall east of the Rockies was set there.
Spoiler: That thing in front of the sign is a normal-size bench...