If you live in Michigan or along the Great Lakes, you often hear weather forecasters talking about lake-effect snow. Have you ever wondered, though, just what exactly is lake-effect snow?
In short, lake-effect snow is the weather occurrence that happens when colder, dryer air absorbs moisture and heat when it passes over a warmer lake. This is most common in the Great Lakes regions, but also happens over the Great Salt Lake.
The most common time of year to experience lake-effect snow is in late fall and early winter, as the larger volume of water in the Great Lakes means it takes longer for them to cool than it takes the air around it to do so.
Deeper into winter, when the lakes start to get colder, there is less difference in temperature between the air and the water, which makes it more difficult for lake-effect snow to form.
Oh, No! There Goes Buffalo!
While we get our fair share of lake effect snow in Michigan, the lake-effect snowstorm that hit Buffalo, New York in October 2006 was certainly one for the record books, as it dropped 22.6 inches of snow. To put that in perspective, the previous record for snowfall from a single October storm in Buffalo was just 6 inches, which was set all the back in 1909.
On October 12-13, 2006, the storm devastated the Buffalo area, knocking down power lines and leaving approximately 1,000,000 people without power. Many trees also went down and, because it was still so early in the season, most of the trees still had their leaves, adding to property damages and complicating cleanup efforts. Within the first few inches of snowfall, damage reports were coming in regularly. The storm still wasn’t even close to reaching its peak at that time.
The Perfect Storm
While large bodies of water provide the moisture needed for lake-effect snow, sometime additional moisture is necessary if wind speeds are too high. In those instances, the wind can move the air too quickly for it to absorb enough lake moisture to form snow bands.
Sometimes, however, upwind of the Great Lakes, the Hudson Bay region can bolster incoming arctic air with plenty of moisture to accelerate and strengthen lake-effect storms.
Arctic air masses play a key role in lake-effect snow. In general, temps around 5,000 feet above ground will have to be at least 23 degrees colder than the lake temperature for lake-effect snow to start forming. If the air mass fails to reach that 23-degree difference, the clouds won’t be able to absorb the necessary moisture to create snowfall. The best you’ll end up with is lake-effect clouds.
The 5,000-foot cloud deck is also important. Any lower than that, and the most you will get is some flurries. By extension, if air masses hit that 23-degree threshold at 7,500 feet above ground, you can expect heavier snowfalls.
One other element that is necessary for lake-effect snow is that the wind needs to be blowing in almost the same direction in the lower atmosphere (i.e., not swirling), as well. As a rule, the heaviest snow bands occur as winds line up with the longest axis of a lake.
The Formation of Lake-Effect Snow
As we’ve discussed, cold, dry air passing over a lake surface that is at least 23 degrees warmer is what leads to lake-effect snow. The greater the disparity between air temperature and lake temperature, the more intense the bands of lake-effect snow will be.
This disparity happens most often in late fall and early winter. It can happen later in the season, but as the lakes finally cool for winter, the temperature of the air mass will have to cool in kind.
The Role of Fetch
Cloud streets are bands of clouds that form parallel to the direction of the wind. A fetch is a path of air located over a lake. The longer the fetch is, the thicker the cloud formation will be. Lake-effect snow then falls downwind of the lake in question.
One of the things that makes lake-effect snow more predictable is that each Great Lake has is own, established optimal fetch direction. A larger fetch leads to powerful lake-effect snow bands, because it takes longer to pass over a lake, which allows more time for greater absorption of the lake’s heat and moisture. Each of the Great Lakes has a wind direction that creates its greatest fetch.
Because of their proximity to each other, two or more Great Lakes can sometimes be effected by the same fetch. For instance, the same southwest wind could blow over both Lake Erie and Lake Ontario, which would lead to lake-effect snowfall at the northeast ends of both lakes. Another example would be a northwest wind that blows across Lake Ontario, Lake Huron, and Lake Superior, producing lake effect snow at the southeast side of each lake.
The longer a lake takes to freeze, the later into the season you can expect lake-effect snow.
Lake-Effect Snow Cities
It’s no surprise that cities nearest the Great Lakes, then, receive the most lake effect snow. Here are some seasonal snowfall averages from 1981-2010 for the larger cities that receive lake-effect snow.
Hopefully the information here will make your weather watching a little more enjoyable this winter. And if you or someone you know is in need of commercial snow removal services, don’t hesitate to contact us online or give us a call at (517) 990-0110 today!