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Weather IQ: How Lake Effect Snow Works

Over 70 inches of snow fell in some areas for the epic lake effect snow around Buffalo. Here is how it happened and what needs to happen to create these events.

BUFFALO, N.Y. — The historic Lake effect snow buffalo saw from Nov. 17-19 dumped a peak of 70-81" of snow. Where at times snow was falling at 3-5 inches per hour. This is a setup the Great Lakes see commonly during the late fall to early spring.

Where they can set up a snow machine that just pumps snow into one area like it's on a conveyor belt for hours to days.  

This snow machine is called lake effect snow. The two main ingredients you need are a consistent flow of cold air and an unfrozen warmer lake.  

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When lake waters are warmer than the environment, warm moist air rises from the lake. When it meets up with the cold air above it condenses into clouds and snow. This cold air will move all this moisture continuously.  

Oftentimes, moisture is the biggest limiting factor for snow events. But this setup creates an unlimited supply of snow-making fuel.   

But for this to happen you need a long enough fetch! 

Yes, lake effect is trying to make Fetch happen! (Mean Girls reference).

Fetch means the distance winds travel over open waters or in this case a warm lake. For lake effect snow to occur, the fetch needs to be at least 60 miles. 

This is the shortest fetch possible to make Lake Effect Snow

This is why the southern and eastern sides of the lakes get the most snow during these events. From persistent winds ranging from the northwest to from the southwest.  

Fetch coming from the NW
Fetch coming from the SW

For forecasting. If the water temperature and the air temperature a mile above the surface differ by more than 55 degrees. That’s when you have the most significant snows that create blizzard conditions and in some cases … thundersnow. 

Credit: WCNC

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