|The effects of a lake effect snowstorm in Mexico, New York,|
near Oswego, in February, 2007. Photo by Sylwia Kapuscinski.
Lake effect snow was blasting northeastern Ohio this afternoon, and threatening the snow belts of western New York over the next few days.
Tis the season.
Lake effect is a hallmark of winter, especially early winter. This time of year, and on into December (and the rest of winter if the lakes don't freeze) cold air often sweeps across unfrozen water of the Great Lakes.
According to NOAA ( and basically every meteorologist), cold winds pick up moisture from the lakes. Relatively warm lake water heats the bottom layer of air, and lake moisture evaporates into the cold air.
Since warm air is lighter and less dense than cold air, it rises and cools. The moisture that evaporated into the air condenses and forms clouds, and snow comes out of those clouds.
|Lake effect snow squalls invade Buffalo, N.Y. in 2007.|
The lake effect snows usually organize themselves into narrow bands. It might be sunny and cold overhead, but you see a dense line of clouds in the distance, which is a lake effect snow band.
If you drive into that snow band, you end up in what is basically a blizzard, with gusty winds and often very, very heavy snowfall.
These lake effect snow bands can cause accumulations at the rate of five inches per hour. Sometimes lightning and thunder punctuate the lake effect snow.
That happened today in northeastern Ohio, where heavy lake effect snow as accompanied by lightning and thunder. Makes for an exciting weather day.
If a lake effect snow band stays over a particular spot for hours or days, you can get several feet of snow, especially near the Great Lakes.
In February, 2007, up to 11 feet of lake effect snow piled up in a few days near Oswego, New York.
Even smaller lakes can produce lake effect snow, if the wind is right. Here in Vermont, long narrow Lake Champlain forms the state's western border. Sometimes, if the wind is from the due north, it goes the length of the lake and can dump a few inches of lake effect snow on the southern Champlain Valley.
If the wind is more from the west, the wind goes through a narrow expanse of Lake Champlain and there's not enough time or water for the cold air to collect enough moisture to produce lake effect snow.
In early winter, late November and December, bodies of water in southern Canada and the northern United States aren't frozen. That means a lot of moisture can get into the early season cold air. Even if there are no lake effect snows, all this moisture contributes to the general cloudy conditions you see this time of year in the Great Lakes and northern New England.
Here in northwestern Vermont, we only receive roughly 30 percent of possible sunshine in November and December, thanks in good measure to lake moisture. The same is true in much of the rest of northern New England, southern Quebec, Ontario and the Great Lakes states.
This, combined with the short days, definitely makes early winter dark and depressing in the North Country.
The weather is forecast to stay cold over the next week to ten days in the Northeast. Often, chilly west to northwest winds will blow across the lakes during that period. So you'll hear more about lake effect snowstorms over the next several days.
Here's a video of a lake effect thunder snow squall today in Ohio: