File:October Snow in Colorado.jpg

English: Snow highlights the rugged mountains as well as the urban and agricultural landscapes of the plains. During this event, winds were predominantly from the north. Air moving southward from the Wyoming-Colorado border blew down-slope toward the South Platte River Valley, and it dropped less snow. On the far side of the river, however, the terrain rises and as the air climbed up-slope, heavier snow fell. The difference in snow totals occurs because air that is descending generally warms and dries. Air that is forced to rise over elevated topography cools, and more water vapour condenses into rain or snow. This pattern of heavy snow in up-slope (north-facing) areas and less in down-slope areas is repeated across the state, most obviously in river valleys oriented in an east-west direction, including the Gunnison and Rio Grande Valleys in Colorado and the Green River Valley in Utah.