The Formation of Snow

Cloud behavior and air currents high in the Rocky Mountains are responsible for the majority of severe weather typically associated with mountainous regions. Air currents are constantly moving across the surface of the Earth, typically in patterns that remain consistent over time. Prevailing winds known as the Westerlies, flow from West to East over the Rocky Mountains. As the air mass travels, it picks up water molecules in vapor form, which will remain vaporous in the higher pressure at low elevations. However, when the air draws closer to the mountains, it is forced to rise in a process called orographic lifting. 

 Orographic Lifting

As elevation increases pressure begins to drop, and the water vapor begins to cool until it reaches the dew point. Once the dew point is reached water vapor condenses in the air into small water droplets. These droplets can be seen as cloud formations. Precipitation can follow directly after the dew point is reached in the form of rain, sleet, or snow. Precipitation will have the highest concentration on the windward side of the mountain as the clouds begin to drop along the peak of the mountain. This causes the air to warm once again, turning the water droplets back into vapor in the atmosphere. This is how rain, sleet, and snow are formed over Aspen Mountain. 

Skiers enjoying the Powder of Aspen Snowmass 

The average dew point for November over Aspen is 25 degrees Fahrenheit. The probability of snow falling is calculated with respect to the time of year in question. Mid-October is when snow begins to accumulate more consistently with an 18% chance of snow on average. This percentage continues to rise until it peaks around February 3rd, with a 52% chance of snow daily. This consistent snowfall is the reason Aspen remains a world renowned ski resort. 

Probability of Daily Snowfall

Average Dew Point

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     <http://www.wisegeek.com/why-do-mountains-seem-to-attract-clouds.htm>.

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http://1.bp.blogspot.com/-f4r9MGLVZ7k/T4dCxhQvboI/AAAAAAAADI/VnZ8UK3uiZo/s1600/05-        25c-lifting-orographic.jpg

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