For the first time in a long while, we had a white Christmas. It was the second major snowstorm of the winter. In fact, December was one of the snowiest on record with just over 29 inches. One of the biggest factors for all the snow once again, was the Lake Erie snow machine. So, how does this machine work? Well it boils down to three main factors that influence fringed machine: an unfrozen Lake Erie, the prevailing winds from the northwest, and elevation just southeast of Cleveland.
Let’s start with Lake Erie, it is the smallest by volume of the Great Lakes. It is also the shallowest and most southerly. As a result, it heats up quickly in the summer and holds that heat longer throughout much of the winter. This prevents the lake from freezing over and allows for the next factor to take effect, the prevailing winds.
Lake Erie is oriented primarily east-west. This happens to be the general direction of prevailing wind and weather movements. In the winter, the weather pattern is more typically northwest to southeast. When cold dry air masses move over the warmer water of Lake Erie, large quantities of moisture are picked up by the air mass and carried inland over northeast Ohio. Then the final factor kicks into play, elevation.
Cleveland sits at nearly the same elevation as Lake Erie. As you travel east and south, elevation changes rather dramatically, thus the reason for Cleveland suburbs to be called Shaker, Cleveland “heights” and North Ridgeville. These locations are about 200 feet higher in elevation than downtown Cleveland. This higher elevation continues south and east towards Chardon, Burton and Hiram and their elevations are 300-400 feet higher in elevation than Cleveland. The increase in elevation means that the air masses carrying moisture from the warmer waters of Lake Erie are swept higher into the atmosphere by the topography of northeast Ohio. This cools the air quickly and results in water vapor condensing into snow. As a result, eastern Cuyahoga, Lake, Geauga and Ashtabula counties receive the most lake effect snow and are considered the primary snow belt. If the winds shift more from the north and northwest, the snow will be carried further inland and lake effect snow will impact the secondary snow belt regions, Medina, northern Summit, Portage and Trumbull counties. Lake effect snow can fall from November through January, or at least until Lake Erie freezes.
Now that we know about lake effect snow, what is snow? Snow is made up of snowflakes. Snowflakes are formed when water vapor high in the air cools and condenses. You can watch this on a cold, frosty car window. When you breathe out to melt the frost on the window, the water vapor escaping your mouth condenses on the cold window and begins to grow into feathery crystals. Clouds themselves are huge collections of water droplets suspended in the air. If the temperature is cold enough, some droplets freeze and become ice crystals.
Water vapor surrounding the ice crystal will condense around it and crystalize. Snowflakes can move up and down in clouds many times, each time changing shape. If the flake grows too heavy to be suspended by moving air, it will fall through the cloud and float downward. The reason snowflakes are symmetrical is that each point or branch of the flake grows at the same time and under the same conditions. No two snowflakes are the same (at least the feathery dendrite kind) because each one has a different and complex path during formation, resulting in different sizes, shapes and designs. So how do we know that is the case? Well the thanks go to William Bentley for proving that no two snowflakes are the same.
William “Snowflake” Bentley was the first person to actually photograph individual snowflakes. In 1885, after years of failures, Bentley finally was able to attach a camera to a microscope and photograph individual snowflakes. During his career, he would go on to photograph over 5000 different snowflakes. Snowflakes come in all sorts of forms, from “plates” to “dendrites” and many shapes in between. One thing in common is the hexagonal shape of most, but not all, snowflakes. This general pattern of snowflakes is a result of the molecular shape of ice. The molecular structure of ice is what is called a hexagonal lattice. This lattice creates the foundation for shape of most snowflakes, including the common 6-pointed snowflakes. Temperature and humidity play a major role in the shape of snowflakes. The ideal temperature for forming dendrites is near freezing and between 15 and -5oF. Low humidity conditions typically form “plates” and “columns” whereas high humidity often forms the 6-pointed dendrites. You may have heard the saying “it’s too cold to snow”. This is not really the case. When temperatures fall, the moisture in the air falls as snow. By the time it gets very cold, the air is usually dry and there simply is not enough moisture to form snowflakes.
