The Nature of Lake-Effect Snow and Flurries

By Alex Sosnowski, Expert Senior Meteorologist

Dec 2, 2010; 11:14 AM ET

Lake-effect events can unload a great deal of snow in a hurry on unsuspecting areas downwind during a cold air outbreak. Similarly, flurries can pull a sneak attack well away from the Great Lakes.

Seasoned residents around the Great Lakes know all too well about the nature of lake-effect snow.

Expert Senior Meteorologist and snow-chaser Dale Mohler commented, "It is not uncommon to be driving along downwind of the lake shore in clear conditions, then minutes later, a few snowflakes can suddenly turn into a raging blizzard and snow-covered roads."

"While the snow bands tend to lose intensity after a couple dozen miles away from the lake, they can still bring surprise, sudden snowfall well inland," Mohler added.

The bands of snow can extend 100 miles or more inland during the right conditions.

Hilly areas, such as in the Appalachians, often enhance the snow.

People often comment, "Where did this come from? You guys were not forecasting this!"

Such is the challenge of pinpointing shifting lake-effect snow and pop-up flurries during a cold air outbreak in the Northeast.

In the case of lake-effect snow and flurries, the lake water adds moisture and warmth to the air, making it unstable.

The result is often "streets" of snow (lake-effect) originating from the lakes.

Sometimes, break-off flurries and heavier snow squalls can occur well away from the lakes in the Appalachians.

While bands of lake-effect snow tend to line up with the wind, flurries and snow squalls can show up out of nowhere many miles away from the Great Lakes.

The snow squalls are the winter cousins to summertime thunderstorms, while flurries would be similar to summertime showers.

Snow squalls and flurries can hit one part of a town and not the other, just like a summertime downpour. They can bring gusty winds and low visibility for a time.

Unfortunately in the winter, paved and concrete surfaces can become snow covered and even icy in a matter of seconds.

Such phenomena have contributed to multiple vehicle accidents on highways in the region more than once, such as on Interstate 80 in Pennsylvania.

Incidents of this sort have been investigated in great detail by AccuWeather.com's forensic meteorologists.

The Nature of Lake-Effect Snow and Flurries