What we call ‘snowflakes’ can only occur naturally high in the atmosphere. They are a special sort of precipitation that’s formed when super-cooled water droplets crystalize (freeze) molecule-by-molecule into hexagonal prisms. This results in each snowflake being unique!
Did you know Rockford receives just 37 inches of snow per year? And that it’s only on the ground for about two-thirds of the winter? That’s not nearly enough for a snow park! So we use a creative way to stay open – we make the snow ourselves!
But how can we make our own snow if snowflakes can only occur high in the atmosphere? Luckily, snowflakes are not the only type of snow. Sometimes, instead of a flake, water crystalizes as a grainy, compact pellet. These little beebee-sized balls are called “graupel” snow, and are caused by melting and re-freezing. This is the type of snow that our snow machines make at Alpine Hills.
Man-made snow goes through much of the same freezing process as natural snow. Snow-making machines are placed at the top of a slope, and then spray small water droplets into the air while exposing them to a nucleation particle so they freeze as they fall through the air.
Three main factors are considered when making snow:
It can take a large amount of water to make snow. Most systems use 200,000 gallons to cover an acre with one foot of snow. Modern technology is able to measure water to such a fine point that snow machines can actually be more efficient at making snow than Mother Nature!
Dust and other biological particulates in the air play a part in this freezing process. By ever-so-slightly affecting the air and the water droplets, the water can freeze at a higher temperature than would otherwise be necessary (32 degrees Fahrenheit). This process is called “nucleating.” It’s how snow can still “stick” even if the temperature is barely at or even above freezing.
Temperature isn’t the only factor that must be properly gauged to make snow. Atmospheric humidity must also be just right, otherwise the graupel snow from the machines will either melt to water or evaporate straight into a gas! The process of evaporation is called sublimation, and it happens when there’s not enough humidity already saturating the air. If the humidity is too high, however, it’ll take longer for the snow to freeze, as there’s not as much space in the air for the heat to escape the water and turn to ice.
Next time you see the snow machines at work, you’ll know the science behind the mountains of fun at Alpine Hills!