skiing Alta powder"The Greatest Snow on Earth" is more than a catchy slogan. It is a scientific fact that Utah's snow is lighter and drier. Moisture rises from the Pacific, climbs the Sierras and gains altitude when it hits the jet stream. As the altitude increases, the air gets thinner and colder and passes across the dry western deserts. The expanding dry air over Utah's high altitude desert causes the moist jet stream air to thin one final time, forming very fine molecules with a ratio of roughly three parts air to one part water. Then these molecules scale the Wasatch mountains and dump very light, very dry snowflakes in Alta and surrounding ski areas.  Finally, Alta is perfectly positioned to receive lake effect snow from the Great Salt Lake, sometimes doubling Alta's storm totals compared to nearby ski areas.  All of this adds up to Alta's yearly average of 547 inches (13.9 meters) of total snowfall.