Lake effect snow is the defining feature of winter for the Holland Patent area and Tug Hill Plateau, located just to our north. Roughly half of our seasonal snowfall total comes from lake effect events, with that number being as high as 85% for locations in the "bullseye" of the lake effect zone-the Tug Hill Plateau and western Adirondacks.
What is lake effect snow?
Lake effect snow refers to snow produced from cold air blowing over a relatively warmer body of water, evaporating some of the water, before it condenses in the colder air, and falls back to Earth in the form of snow. Unlike the air masses of other snow storms, the air that blows over the body of water would otherwise be too dry to support snowfall.
As we can see in this diagram provided by the NOAA, the warmer water evaporates and rises. The more that the water vapor can rise, the cooler it becomes. This results in the formation of larger snow crystals, and therefore, higher snow totals. The amount of space that the water vapor has to rise is determined by two factors: the elevation of the land below, and the inversion height in the atmosphere. The first of these two factors is pretty straightforward. The cloud deck (base of the clouds) generally stays a certain distance above the land, so as the land rises or drops in elevation, the clouds will generally do the same. This is the reason why areas of higher elevation tend to receive more snow. The image on the right shows the average yearly lake effect snowfall of the Tug Hill and western Adirondacks region. The map on the left shows the elevation of this region. See the correlation?
The second of these two factors is a bit more complicated. Given that the water vapor is warmer than the surrounding air. Just as we were taught in elementary science, warm rises while cold sinks. In this case, as the water vapor continues to rise, it is gradually cooled off by the surrounding air. Eventually, the water vapor is no longer warmer than the surrounding air, and stops rising. The height at which the water vapor stops rising is known as the inversion height. The higher the inversion height is, the higher the clouds can build, and the stronger the lake effect snow will be.
The diagram below demonstrates both elevation AND inversion height when it comes to lake effect. We can see that as the land rises to the right of the lake, the bottom of the cloud layer also rises. That is the elevation factor. The dotted line represents the inversion height. We can see that rising over the lake, even though the ground elevation is constant. As the inversion height rises, the cloud itself becomes a lot taller.
It's all in the wind
Lake effect snow is, without a doubt, the hardest forms of winter weather to predict. This is largely because of the driving force behind it: wind direction. The tiniest changes in the wind direction and speed, changes that wouldn't make an ounce of difference in any other type of winter storm, can literally make the difference between our school district (or any place within the lake effect belt) getting feet of snow during one storm or getting no snow at all. The wind direction determines both how strong the lake effect is, and where the snow falls. Because lakes are irregularly shaped, the direction of the wind determines how much of a distance the air has to blow over the lake. This is known as the fetch. For example, if the wind was out of the north, it would have far less of a fetch to pick up moisture over Lake Ontario than if it was blowing out of the west. It is no coincidence why the eastern shore of Lake Ontario has a much higher average yearly snowfall than the southern shore. The map on the left compares the fetches based on a west wind versus a north wind, and the map on the right shows the differences that the eastern and southern shores have in their average snowfall.
Because lake effect bands are very narrow, with the average band (the line of snow, such as the cover image for this page) width being around 20 miles, they impact only a very small and localized area. The limited area covered by a lake effect snow band at any given time makes the direction in which the wind pushes the bands very important. For example, if you hold a pencil at one end, and pivot it just 15 degrees, almost all the area previously covered by the pencil is no longer covered. To further complicate matters, the wind direction can constantly shift throughout the duration of a lake effect event, and models often struggle to pinpoint how fast and when these minute, yet impactful, changes in wind direction will occur. Below is a map of the various wind directions Central New York and Northern New York can face during a lake effect event. The numbers represent the degree on a compass the wind would blow from in any given direction. As you can see, the Holland Patent region is aligned with a 285 degree flow.