Lake-effect snow explained

It’s a bird! It’s a plane! Nope, it’s lake-effect snow!

Every year, the U.S. Snowbelt is often graced with very heavy snow thanks to cold air being shoved across the Great Lakes during late-autumn and winter - and it is happening right now. But how exactly does this work?

Lake effect snow is only possible when the lake’s water temperatures are much warmer than the air flowing over them. This means the lakes have very little to no ice on them and the air moving across the bodies of water is likely from the north or northwest, which is much colder than air to the south.

When cold winds kick up and flow across the warmer body of water, snow clouds form and grow. The elevation of the land downwind from the body of water is important. The more these clouds rise, thanks to the increasing land elevation, the better the instability for snowfall to occur.

One final detail needed for the lake-effect snow to accumulate is that temperatures on land need to be near or below freezing for any snow to pile up. The heaviest bands can produce 2 to 3 inches or more of snow per hour in some cases causing white-out conditions and dangerous slick roadways.

Lake-effect snow bands are quite thin but can be very long. They are usually no more than 3 miles wide according to the National Oceanic and Atmospheric Administration, but can be very long depending on which lake they are moving off from.

Lake-effect snow tends to occur in the late-autumn and wintertime because consistent cold air usually hasn’t been around yet to help the lake freeze over. Therefore, abundant moisture is available when a cold air mass moves across the body of water.

As long as the body of water is wide enough and in an area where very cold air from the north or northwest can move across it, lake-effect snow can occur. That’s why this is usually seen in the Snowbelt states which include Michigan, New York, Pennsylvania, Ohio, Illinois, and Indiana.

The Tug Hill Plateau in New York regularly receives more than 20 feet of snow each winter thanks to the help of the lake-effect snowfall off Lake Ontario. Further north in the Michigan Upper Peninsula next to Lake Superior, records of 390 inches or 32.5 feet have been set across several communities thanks to the lake-effect!

When the forecast calls for it, you can watch for the lake-effect snow bands on our interactive WeatherRadar!