The Lake Effect

Reader Contribution by Cindy Murphy
Published on January 5, 2009
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Look at any USDA Cold Hardiness Map and you’ll see a thin band along Lake Michigan colored different from most of the rest of Michigan.  Weather Channel maps in winter often show that same area colored white when the rest of the state is colored green.  Though it may seem as if the map-makers run out of the color they’ve been using when they get to the western side of the state, Lake Michigan is the actual cause of the change in color. 

Lake Michigan keeps this area more temperate than the rest of the state.  Here, along the shore, the wind passing over the cooler lake water keeps our summer temperatures milder.  This gives us a Zone 6 cold-hardiness rating, a zone warmer than most of the rest of the Lower Peninsula – even just a few miles inland from the lake.  In winter, the lake is warmer than the air, resulting in less extreme fluctuations in temperatures.

It’s this relatively warm water in comparison with the cold winter wind that produces the phenomena known as “the lake effect,” and it generates a tremendous amount of snow.  Artic air blowing over the Great Lakes picks up moisture from the water, and deposits it inland as snow.  Areas east and southeast of the lakes are where the lake effect snows are dumped because artic air masses typically come from the west.  So while that same artic air is clearing up the skies over most of the rest of the country, Great Lake communities are fueling their plows and preparing to get buried in snow.  Thirty to sixty percent of annual snowfall in these communities are due to the lake effect.

The local radio station here reported that the South Haven area has had 50 inches of snow since November of this year; 2 feet were on the ground on Christmas Day which makes it the whitest Christmas we’ve had in the past few years.

Not all of this snow is lake effect; the low pressure cell of winter storms that hit much of the country recently is responsible for some of it.  It’s the air flow that typically comes behind the storm’s front that produces lake effect snow squalls.  The wind can last for days, making lake effect snow bands persistent.

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