The Art of Snowmaking at King Pine

Posted by Joe Joyce February 14, 2009 at 9:13 am

Out of all the weeks I could have chosen for snowmaking this winter, I end up choosing the week of the February Thaw. I am not complaining. Though temperatures made it a bit tricky for snowmaking, the weather was fantastic. Spring skiing at King Pine, a small mountain in New Hampshire with an elevation around 850 ft. What King Pine lacks in size, they make up in charm. What a great little family resort which has everything to keep the kids and family entertained on a budget! Not only does King Pine have downhill skiing and cross country, but they also have ice skating, Horse-ridden sleigh rides, tubing, indoor swimming, snow shoeing and great camping and swimming around Purity lake in the warmer summer months. Our stay was an absolute delight…but this visit was not all play. It was about learning the art of snowmaking!
Right off the bat I knew it was not going to be the best weather for snow making. Highs were in the 30’s, even Near 50 by Wednesday…so we were going to have to time the weather during odd hours..early morning or late at night, if we were going to be able to make any snow at all. Honestly, if I was not there King Pine would not have been making snow, but they were nice enough to entertain me.
So how do snow-makers determine if the conditions are right? It turns out they need a lot more information than they can get from an ordinary thermometer with a temperature at or below 32 degrees. Standard thermometers measure the dry bulb temperature of the atmosphere; but the most important factor for snow conditions is the wet bulb temperature. Wet bulb temperature is the lowest temperature that can be obtained by evaporating water into the air at a constant pressure. Liquid or solid water cools itself by evaporating some water as water vapor. When there is more water vapor in the atmosphere, water or snow can’t evaporate as much because the air is already saturated with water to a high degree. Consequently, water cools more slowly when the humidity is high, and more quickly when the humidity is low. In a nutshell, as the temperature and humidity drop, the amount of snow made per hour goes up. To make quality snow, the Wet Bulb Temperature needs to be 28° F or less. The lower the humidity, the higher the actual air temperature can be.

For example, in the rare circumstance that we have less than 15% humidity, King Pine can make quality snow when the actual air temperature is as high as 36° F. Conversely, during times of high humidity or 80% or more, it may not be possible to make snow even if the actual air temperature is less than 32° F. Once the temperature drops below 25° F, it is possible to make snow regardless of humidity. In fact, the ideal temperatures for snow making is between -5 to 15 degrees. These kind of conditions will create that nice dry snow. Dry snow has a relatively low amount of water, so it is very light and powdery. This type of snow is excellent for skiing because skis glide over it easily without getting stuck in wet slush.
One of the advantages of using a snow maker is that you can make sure the slope’s surface level always has this ideal, powdery snow. But Wet snow also plays an important role on ski slopes, however. Resort owners use this denser snow to build up the snow level on well-travelled trails. Many resorts build up the snow depth this way once or twice a year, and then regularly coat the trails with a layer of dry snow throughout the winter.

With the advanced technology of snowmaking, people have come to expect well groomed trials with wide open terrain and no rocks…no matter the weather. To keep the mountain in such great shape it does come at a cost. King Pine estimates they spend between 25,000-40,000 dollars on snowmaking each year depending on how much cold and snow winter brings. Because of the expense of making snow, ski resorts have to develop a good strategy for when and where they are going to use their machines. A lot of the work involved in snow-making is the task of balancing the cost of running the machines with the benefits of extending the ski season. Efficient snow-makers make sure they don’t waste power making snow where it won’t do any good, and they are very careful to make snow only when it will stick around. Water is not a huge expense for ski resorts, however; and pumping this much water isn’t incredibly bad for the environment. Most resorts pump water from one or more reservoirs located in low-lying areas. The run-off water from the slopes feeds back into these reservoirs, so the resort can actually use the same water over and over again.

Many snow-makers describe the job as a challenging marriage of science and art — the basic elements are precise weather measurements and expensive machinery, but you need instinct, improvisation and creativity to get it exactly right. To cover several ski trails with manmade snow, you need a lot of water. It takes about 75,000 gallons of water to create a 6-inch blanket of snow covering a 200×200-foot area .
At King Pine, Snowmaking goes like this….
pump 1500 gallons of water per minute
each gallon of water weighs 8.33 lbs
multiply the two (gals per min X weight) you get 12,495 lbs of water being turned into snow per minute
divide that number by 2000 (# of pounds in a ton) you get 6.2 tons of snow per minute
multiply that by 60 (minutes per hour) that’s 375 tons of snow per hour!

For every snowmaking line leading to an air/water gun hydrant there are 2 pipes. One carries water, one carries compressed air generated from huge deisel compressors. Each line is under tremendous pressure. For every snowgun there are 2 valves. They regulate the amount of water and air that gets sent to each gun. Each gun has very small holes in the head that pulverize the water into extremely small particles. When the water and air are mixed at the proper ratio, the force of the compressed air causes the water to cool rapidly and the outside air temp (wet bulb) causes the moving and cooling water vapor to freeze, making homemade snow.

As the new snow particles continue to fly through the air away from the gun, the water content in each particle is reduced with the amount of “hang time”. So the snow that lands the farthest from the gun will be the driest (hint, hint). In general, it is a good idea to stay far away from any snowgun that is operating on an open trail, but this fact should be an extra incentive to ski the snow farther from the gun…for safety and the fresh snow!

It was a great time at King Pine. There is no better way to spend the winter with your family than outside skiing, skating, sledding, tubing…whatever! Get outside and enjoy the weather.

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