Cold winds moving across large warm lakes are the result of lake-effect snow. The water vapor is picked up by the wind, then it freezes before being taken to shore. Narrow and intense bands of participation are produced by the effect. Many inches of snow can be built up within a short amount of time by this type of snowfall. Areas where the snow falls are called snowbelts, a lot of places worldwide are affected, but mostly it occurs in the Great Lakes regions of North America.
In order for lake-effect snow to take place, the surrounding air needs to be significantly cooler than the air close to the expanse of water. There are key factors involved in the production of lake-effect participation. Fetch, instability, wind shear, upstream moisture, upwind lakes, and orography or topography are all features which determine lake-effect events. A difference in temperature of 13 degrees C must be evident between the surrounding air and the lake temperature. The lake temperature must be warmer than the air temperature. The distance an air travels across water is known as its fetch. A distance of 100 km is required for lake-effect precipitation.
The water vapour condenses and falls as snow around 40 km from the lake. When a lake starts to freeze the chances of it producing lake-effect snow are lowered. The heat energy reduces as the lake begins to freeze giving less of a chance for squalls. In the Great Lakes region cold winds usually occur from the northwest. The southern and eastern shores of the lake are normally hit the hardest with the lake-effect snow episodes. The Great Salt Lake in the US never freezes, therefore there is a lot of lake effect snow mainly in the southern and southeastern sides of the lake.
It is not only in the US, but other countries also experience lake-effect snow. Lake Winnipeg in Canada starts producing this type of snow at the end of October. This is relatively short lived as the lake begins to freeze towards the end of November, stopping the lake-effect snow from forming. Similar snowfalls occur in regions close to the Black Sea and Adriatic Sea. The North Sea can also have an effect on snow in the UK; even though the snow comes from the sea it is still known as lake-effect snow. This type of snow gives the most snowfall in a matter of hours, a couple of feet can fall in a short amount of time.
