Lake effect snow is a common phrase that people living in the Great Lakes regions know too well. The end result of this weather happening can deposit many inches, or even feet of snow on the leeward side of the lakes.
Cold winds moving across the lakes are often colder than the temperature of the water, and, when this happens water vapor is collected, and deposited as snow on the leeward side. If the air is not cold enough to produce snow, it will produce lake effect rain.
If the air is much colder than the water temperature, it can also produce thundersnow, a snow storm with thunder and lightening.
The worst of the lake effect snows occur on the heels of an actual storm front, that has passed over, but is followed by cold blustery winds. These winds are the culprits that cross the lakes and produce what are sometimes called snow bursts.
There are several factors that effect lake effect snow.
1. Instability. If the temperature difference 4,900 feet above sea level and the lake is 13 degrees C, more moisture and heat are transported vertically from the lake, forming bigger snow clouds and, consequently more lake effect snow.
2. Fetch. Fetch is the distance that the air travels over the water, collecting moisture as it goes. The further the air mass travels, the more it collects, and the bigger the snow fall.
3. Directional and Wind Speed Shear. If the directional shear of the wind at the 700 MB level is 30 or below, an organized band of precipitation will form. Likewise, if the velocity is faster, the storm system will travel further inland.
4.Upstream moisture. If the humidity is high upstream from the front, it will collect more moisture, it will produce a larger quantity of clouds, and snow.
5. Topography. If the leeward side is elevated, it will cause the precipitation to drop more quickly, and dry out the storm faster.
6. Lake freezing. Ice formation on the lake affects both the fetch, and the amount of moisture that rises, and is available for the production of snow clouds.
The Tug Hill Plateau, north of Syracuse, New York and east of Lake Ontario, is one of the most famous examples of lake effect snow. Consequently, the city of Syracuse can average over 100 inches of snowfall per year. Parts of Oswego and Lewis counties can average over 300 inches in a season.
Other hard hit areas around the Great Lakes are, western and northern Michigan, the Upper Peninsula, northern Indiana, and eastern Ohio, in the Cleveland area.
http://www.islandnet.com/~see/weather/elements/lkefsnw1.htm
http://www-das.uwyo.edu/~geerts/cwx/notes/chap10/lake_effect_snow.html
