Why does lake effect snow usually occur on the downwind shores of the Great Lakes in early winter?
The lower layer of air, heated by the lake water, picks up water vapor from the lake and rises through colder air. The vapor then freezes and is deposited on the leeward (downwind) shores.
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speed, amount of ice cover on the lake, and topography downwind of lake. increased convergence and lifting on downwind side of lake; hills also a physical barrier to flow, forcing it to rise. Both effects contribute to upward air motion necessary to produce clouds and snow.
Lake-effect snow generally doesn't fall over the water because it needs the friction and topography of the land to bring out the snow. Winds usually blow west to east in the Northern Hemisphere, so the lake-enhanced snow is pushed to the eastern side of the Great Lakes, Miller said.
Anywhere! Lake effect snow can occur over any unfrozen body of water where the fetch is long enough to gather enough moisture to create snow. Lake effect snow can occur over Lake Tahoe, the Great Salt Lake, the finger lakes, and even has been reported over rivers in the Midwest!
Lake-effect snow is a frequent contributor to our seasonal snowfall in Chicago and with Lake Michigan almost ice free, the lake-effect snow machine is open for business provided a cold wind is blowing in our favor in the right direction. Nearly 93% of the Great Lakes does not have significant ice cover.
Luckily for people living near large lakes, lake effect snow generally slows down around February. That's when the lakes freeze over, making it impossible for the air to steal moisture away from the lake.