Have you wondered what weather forecasters mean by the term lake-effect snow? If you're a Great Lakes traveler, you most likely have come in contact at one time or another with this common area weather pattern. The areas hit the most by it border the Great Lakes which include some of the largest cities of the region as well as more rural towns. In fact, some of the worst snowfalls in the United States occur as a result of lake-effect snow.

This isn't a singularly Great Lakes region phenomenon. A body of water needs to be large enough to experience it, a category that the Great Lakes definitely fall into. This coupled with the fact that the lakes are so close to each other makes lake-effect snow something to which this region falls prey.

Lake-effect snow, also known as LES, generally occurs from the late fall through the winter. It is created by cold winds passing over warm water. These cold blasts originate in the polar regions of Canada and pass over the water of the Great Lakes which causes warmer air and moisture to form. The warm air rises above the cold air and creates the snow and cloudy visibility conditions that we know as white-outs. This occurs on the leeward, or downwind, side of the shorelines.

There are environmental factors that are responsible for varying degrees of lake-effect snow. Not all areas get hit with the same impact. The downwind lakeshore areas have it the worst and are called snowbelts. Wind speed and the amount of shoreline the passing cold air has to cover are just two of the ingredients needed to dump snow in these areas. This can cause problems such as impaired visibility and other dangerous driving conditions.

According to Keith C. Heidorn, PhD, at The Weather Doctor, there are seven snowbelts associated with the Great Lakes region. They occur near the following areas:

• Southeastern Lake Superior (Michigan)
  
• Eastern Lake Superior (Ontario)
  
• Eastern Lake Michigan (parts Michigan and Indiana)
  
• Southeastern Lake Huron (Ontario)
  
• Georgian Bay (Ontario)
  
• Southeastern Lake Erie (parts of New York, Pennsylvania and Ohio)
  
• Southeastern Lake Ontario (New York)
  

Forecasting lake-effect snow has become easier as meteorology technology improves. That is not to say that forecasting still isn't challenging. Like other weather patterns, there are various meteorological factors to take into consideration such as wind speed, temperature, and relative humidity. If you live in this area, you know the old joke about waiting five minutes if you're unhappy with the weather because it's sure to change. Joking aside, this does make tracking lake-effect snow more difficult.

Besides your local news and radio services, an excellent resource for lake-effect snow forecasts is the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service website linked at right. You can click on your area of the country or type in a search for the current lake-effect snow forecast. Keeping up on this or any type of weather will make for a safer trip for you and your loved ones.

References:

• Haby, Jeff.  Lake-Effect Snow Forecasting.  Weather Prediction Education.  February 2009 (date accessed).
  
• Smith, Bruce B.  Lake Effect Snow.  NOAA's National Weather Service - Central Region Headquarters.  December 2, 2008.  February 2009.