WEST MICHIGAN — The state of Michigan is known for many things: home of the automobile industry, four ideal seasons, Beer City USA, and so much more. However, the top thing that makes Michigan stand out the most is our incredible Great Lakes! Michigan has more freshwater shoreline than any other state in the nation, and these vast Great Lakes generate feet and feet of lake effect snow every year.
Lake effect snow boils down to three key ingredients: the ample moisture from our Great Lakes, unwavering cold Canadian air, and steady winds. While those ingredients might not seem like much, the correct amount of each can lead to 2" to 3" of snowfall per hour in one given location.
When cold Canadian air sweeps in from the north, it is met with the relatively warmer and unfrozen open waters of the Great Lakes. Unlike air, water takes much longer to change temperature. For example, think about an average day! A location in West Michigan could have a high temperature of 60 degrees during the daytime hours and an overnight low temperature of 30 degrees. That's a 30-degree difference in a matter of hours! Water, on the other hand, would need a matter of months to be able to change 30 degrees.
The warm moisture from the Great Lakes almost combines with the cold Canadian air. As air warms, it naturally becomes less humid and less dense! When air is less dense, it rises. As the air mass rises, it becomes cooler and cooler. That's because temperatures tend to be cooler higher up in the atmosphere.
Through convection and turbulence, narrow and long clouds form along the steady wind stream. Once the cooler and moist air reaches land, it creates snow! As we know in West Michigan, lake effect snow bands can vary in intensity! Some lake effect snow bands are light, while others can produce quickly accumulating snow and limited visibility. This is what makes traveling in lake effect snow very difficult, in addition to forecasting it. Snow accumulations during a lake effect event can vary from a trace to several inches over a short distance.
When forecasting lake effect snow, our FOX 17 Weather Team must look at various atmospheric elements! First, meteorologists take into consideration the difference in temperature between the lake water and the air. The greater the difference between the two, the greater the chance for lake effect snow to develop. Forecasters look for the temperature of the air about 5,000 feet above the surface to be at least 13 degrees Celsius colder than the lake temperature. If the difference is greater than that, there is an even greater chance for stronger bands of snow.
For example, do you remember the large lake effect snow event between November 16th through November 20th that resulted in 30.8" of snow accumulation in East Grand Rapids? Well, the difference between air temperature high up in the atmosphere and the water temperature was well over 20 degrees Celsius. Since that is a greater difference than 13 degrees Celsius, that gave the FOX 17 Weather Team a strong indicator that the event could produce heavy snow.
Meteorologists also look at the available moisture, if there is a system passing, the wind direction, and the fetch.
Fetch is the distance the wind travels over the open water. The longer the fetch, the greater amount of moisture. This can lead to greater amounts of lake effect snow! A good example of fetch is the difference between Lake Michigan and Lake Erie during a westerly wind lake effect event. Again, looking back at the event between November 16th through November 20th where East Grand Rapids received 30.8" of snow accumulation. Within that same time frame, parts of New York saw over 70" of snow accumulation. There were several factors that were very similar for West Michigan and New York during that event, including the cold air and steady winds. A large part of why New York saw so much more snow accumulation was because of the fetch! More moisture was able to be picked up from the Great Lakes, which resulted in more snow.
In addition to the fetch, the wind direction is also a key component to forecasting lake effect snow! The wind direction shows meteorologists where the heaviest snow accumulation is likely. Even the smallest changes in wind direction or speed can tremendously change the areas impacted. Although lake effect snow can occur with any wind direction, the most common and heaviest-hitting lake effect normally results from a westerly wind component in Grand Rapids. Kalamazoo, on the other hand, can receive heavier snow bands from a northwesterly wind. The reason this is the case all boils down to the fetch, or the distance the air travels across Lake Michigan.
If it wasn't for our truly great lakes, we wouldn't see nearly as much snow in West Michigan during the wintertime.
