Lake Effect Snow – How Does it Happen

Lake effect snow from the Great Lakes occurs when warm lake water evaporates and dry cold air currents slide over the region. Water retains the heat more than air. This causes some open water in the Great Lakes to evaporate into the air and warm it. Rising into the atmosphere, this warm, wet air cools as it travels, turning into clouds that dump the frozen water on downwind land. These lake effect snow belts are identified due to a continuous pattern of snow during the winter months.

The lake effect snow is explained in a simple video showing the Great Lakes region’s major areas where this type of weather pattern prevails. This pattern occurs when snow falling on the lee side of a lake, generated by cold, dry air passing over warmer water, especially in the Great Lakes region.

How Lake Effect Snow Forms

Lake Effect Snow
Lake Effect Snow – From NOAA

The cold, dry air, often originating from the west and Canada, moves across the Great Lakes’ open waters. As the cold air passes over the unfrozen relatively warm waters of the Great Lakes, warmth and moisture are transferred into the lowest portion of the atmosphere. The air rises, clouds form and grow into a narrow band that produces 2 to 3 inches of snow per hour or more.

Wind direction is also an indicator of will receive lake effect snow. For example, heavy snow may be falling in Caseville, while the sun may be shining in Bad Axe. The physical barrier that Sand Point represents also has some impact on weather patterns on the south shore of Saginaw Bay.

Recipe for Lake Effect Snow

Conditions must be absolutely correct for the formation of lake effect snow to occur. Without all the elements in place, the chances of snow development are diminished. Here are the typical conditions for snow development.

Open Warm Water – The lakes need to be open and relatively ice-free. The lake water also has to be warmer than the air above it so evaporation can occur.

Light Dry Winds – As the wind gently whisks over the warmer lake water it picks up the moisture and it rises to the upper atmosphere. If the winds are too strong, over 25 knots, then it cant pick up great volumes of moisture.

Land – Once this moisture-laden wind hits land, the speed intensity is reduced, and the air is forced up further, causing it to freeze and eventually drop as snow.

Lake Effect Snowbelt Map

Lake Effect Snow Belt Great Lakes
Lake Effect Snowbelt Map – Courtesy the University of Michigan

The greatest accumulations typically occur in Canada on the Bruce Peninsula and within Georgian Bay. The Upper Thumb also experiences lake-effect precipitation during prevailing southwest wind winter storms or when Saginaw Bay is significantly frozen over.

Great Lake Areas With Greatest Impact for Lake Effect Snow

  • Michigan Upper Peninsula – The Porcupine Mountains, Keweenaw Peninsula to Whitefish Point
  • Western Michigan – Traverse City, Muskegon, Grand Rapids, Kalamazoo, South Bend, and Elkhart
  • Lake Ontario & Erie –  Cleveland, Ohio to Buffalo, New York. Western New York
  • Lake Huron – Georgian Bay, Bruce Peninsula, Western and Upper Michigan Thumb

Climate Change and Lake Effect Snow

According to the Great Lakes Integrated Sciences and Assessments Program, “snowfall has increased in northern lake-effect zones in the Great Lakes basin even as snowfall totals in Illinois, Indiana, and Ohio have declined with rising temperatures. Warmer Great Lakes surface water temperatures and declining Great Lakes ice cover have likely driven the observed increases in lake-effect snow.”  As temperatures rise, resulting in a warmer Great Lakes, lake-effect zones will have higher lake-effect snowfall. Areas in the southern great lakes may see more lake-effect rain.



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