Snow is an umbrella term that covers anything from tiny flurries and clumps that fall during blizzards to man-made stuff on ski slopes.

However, these types of snow aren't the same in their formation or their use for recreation, said Nicole Stockey, president of the Penn State ski team.

"I was in Colorado over break, and they had two feet of natural snow," she said. "It was like falling on a pillow, but with artificial snow it's more like falling on concrete."

The reason for the differing textures of natural and artificial snow is the way that they are made, said Dennis Lamb, professor of meteorology.

Natural snow begins in the cloud, which is made up of liquid water droplets, Lamb said. When the temperature is below freezing, the droplets freeze to ice nuclei that must be present in order to initiate snow. The ice nuclei could be small air or pollution particles. The droplets continue to freeze together and eventually form a snow crystal. An individual snow crystal is very small, anywhere from one to five millimeters.

Lamb said snowflakes can be column-shaped, or cylindrical, while "plates" are thin and uniquely shaped.

"I call [plates] classical because they are what people usually think of as a snowflake," Lamb said.

Snow crystals may not maintain their shape because additional droplets may collide and stick to them until the original crystal cannot be recognized.

Temperature determines whether the crystals come out as flurries or as clumps of snow. If the temperature is close to the melting point of ice, then a thin layer of liquid forms on the crystal and enables it to stick to other crystals to form a larger mass in a process called aggregation, Lamb said. Dozens of snow crystals making up a mass forms a snowflake. If the temperature is below freezing, the layer of liquid is frozen, and the crystals do not stick together.

"It would be like trying to make a sugar ball," Lamb said. "It doesn't work because the solid particles have nothing to make them stick."

For this reason, snowballs are difficult to create in very cold weather when the snow crystals cannot stick. However, if the temperature warms up, the snow will become stickier as it melts.

"When it comes to making snowballs, wetter is better because it sticks together," Stockey said.

Natural snow can be used at ski resorts, but because of the limited amount of snow that falls in Pennsylvania, artificial snow is necessary to keep the resort in business, said Tom Matalazage, mountain manager at Tussey Mountain Winter Resort.

"You can't depend on natural snow," he said. "It's just window dressing to make people think about coming out. We rely 100 percent on making snow."

When making snow, first water is pumped into the machine. A high-pressure stream of air from a compressor shoots the water out of nozzles which break the water into tiny droplets.

"Once the particles are out in the air, Mother Nature takes over," he said.

As with snow formed in clouds, the droplets attach to ice nuclei. Some resorts add fragments of bacteria to the water to act as ice nuclei. The droplets freeze instantly into little spheres and fall to the ground. Artificial snow does not form into plates or columns.

"Snow making is best at temperatures below 20 degrees when it is cold and dry," Matalazage said. "The warmer it is, the amount of product drops off, and the process becomes less efficient."

Resorts prefer artificial snow, not only for its reliability, but also because it lasts longer than natural snow. Only six inches will cover the ground, while for natural snow it may take over a foot.

"Artificial snow is much more durable than natural snow because it is much denser," Matalazage said. "It has three times as much water."

Skiers also prefer artificial snow because its density allows for greater speed. Natural snow requires different technique.

"Natural snow is softer than artificial snow," Stockey said. "Artificial snow simulates natural snow, but it is firmer. You can slide better and go faster.

Artificial snow can also be used for snowballs because it can melt and become sticky. Snow angels may not be a good idea for artificial snow, because it is denser and harder, Stockey said.