First Significant Lake-Effect Snows of the Season Expected in the Great Lakes

Brian Donegan
Published: November 5, 2019

As multiple rounds of cold air sweep across the central and eastern United States this week, lake-effect snow will develop in some of the Great Lakes snowbelt locations east and southeast of the lakes.

Lake-effect snow is created when cold, dry air picks up moisture and heat by passing over a relatively warm lake, such as one of the Great Lakes or the Great Salt Lake in Utah.

(MORE: More Rounds of Cold Air Ahead into Mid-November

In this week's case, cold westerly to northwesterly winds from Canada will blow over the Great Lakes, causing snow showers and locally heavier squalls to develop downwind of lakes Superior, Michigan and Huron through Tuesday night. Parts of the Upper Peninsula of Michigan, northern and western Lower Michigan and southwestern Ontario, Canada, will see snow.

Current Radar

Winter weather advisories have been issued by the National Weather Service for lake-effect snow along much of the Lake Superior coast in the Upper Peninsula of Michigan. Winter weather advisories are also up for non-lake-effect snow along a frontal zone from southern Minnesota to central Lower Michigan.

Eight inches of snow fell in five hours on Tuesday northwest of Cusino Lake, Michigan.

By Tuesday night, disorganized bands of lake-effect snow will form east of Lake Erie in northwestern Pennsylvania and southwestern New York and east of Lake Ontario in central New York. These will weaken and diminish by Wednesday afternoon.

A dip in the jet stream will allow cold westerly to northwesterly winds to blow over the relatively warmer waters of the Great Lakes.

A weak disturbance will spread some light snow across the northern and western Great Lakes on Wednesday. Behind it, more lake-effect snow showers and locally heavier squalls are expected late this week as a stronger blast of cold air sweeps across the lakes.

On Thursday, lake-effect snow is likely in the eastern Upper Peninsula of Michigan and western and northern Lower Michigan.

A separate weather system may bring some light snow to parts of the Northeast late Thursday into Thursday night. Lake-effect snow may then develop in the lakes Erie and Ontario snowbelts on Friday.

(MORE: First Snow of the Season in Parts of the Ohio Valley, Northeast?

There could be a break in the lake effect this weekend, but some areas may see more lake-effect snow next week as another round of cold air arrives early next week. This round could be the heaviest of the year so far in some areas, due to very cold air aloft sweeping across the lakes.

Many of the Great Lakes snowbelts have already seen a little lake effect this season, but this could be the first significant event with more than 6 inches of snow in some locations. Given the localized nature of lake-effect snow, accumulations will vary greatly from one town to the next.

(MAPS: 48-Hour Snowfall Forecast

The most likely time of year to get organized lake-effect snowbands is from late fall into early winter, when lake temperatures are at their warmest relative to the colder air spilling over them.

Once the lakes freeze over, the moisture and heat source is lost and lake-effect snow has a hard time developing.

Lake-effect snowbands blanket the Great Lakes region on Jan. 5, 2015, in this high-resolution image from NASA's Aqua satellite.
(NASA Worldview)

Lake-effect snow can happen in October and March as well, though the latter is less common since lakes are at their coldest – if not frozen – and air masses are a bit warmer than earlier in winter.

One of the most memorable lake-effect snowstorms in Buffalo, New York, took place in October 2006, when 22.6 inches of snow fell in the city. Before this, the all-time October monthly snowfall record was 6 inches, set in 1909.

A band of heavy lake-effect snow pummeled the Buffalo area from Oct. 12 to 13, 2006, downing trees and power lines and knocking out power to about a million customers. Many trees still had their leaves, worsening the impacts of the snow.

Lightning and thunder were constant during the height of the storm, according to the National Weather Service. This was due to the unstable environment in place, with relatively mild lake waters at 61 degrees and an air mass just cold enough aloft to produce the heavy snow.

(MORE: Major, Damaging Snowstorms Can Strike in Early Fall

Ingredients Needed for Lake-Effect Snow

While the lake, or any other sufficiently large body of water, provides moisture to aid in the development of lake-effect snow, additional moisture is sometimes required if wind speeds are high.

When winds are whipping across the lake especially fast, they don't have as much time to pick up moisture from the lake and form organized snowbands.

Upwind of the Great Lakes, northeastern Canada's Hudson Bay will sometimes fuel an incoming arctic air mass with ample moisture and produce stronger lake-effect snowstorms.

(MORE: Lake-Effect Season Is Beginning And It's Not Just About Snow

Temperatures about 5,000 feet above ground must be at least 23 degrees Fahrenheit (13 degrees Celsius) colder than the lake temperature for lake-effect snow to develop.

For example, the temperature of Lake Ontario on Monday was 53 degrees Fahrenheit (12 degrees Celsius) off the coast of Rochester, New York. That means an incoming cold air mass would need to be at least 30 degrees Fahrenheit (minus 1 degree Celsius) or colder at 5,000 feet as it passes over Lake Ontario in order for lake-effect snow to form downwind of the lake.

If the air mass does not meet the 23-degree Fahrenheit (13-degree Celsius) threshold, there will typically not be enough instability to force the moist air upward and generate lake-effect snow. At best, you'll just get some lake-effect clouds and maybe a few flurries, because the air mass won't be unstable enough for significant precipitation.

One other ingredient necessary for the formation of lake-effect snow is winds blowing in nearly the same direction throughout the lower atmosphere.

In general, the heaviest single snowbands occur when winds align roughly with the longest axis of a lake.

For example, the winds should be well aligned out of the west, west-northwest or northwest from the surface up through about 5,000 feet for organized lake-effect snowbands downwind of Lake Ontario.

A west or southwest wind would bring the heaviest single lake bands downwind of Lake Erie.

(IN-DEPTH: What Is Lake-Effect Snow?

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.