An upslope wind occurs on the windward side of a mountain range. Some mountain ranges, such as the Sierra Nevadas in California have the west side of the mountain range as the windward side the great percentage of the time. Other mountain ranges such as the Rocky and Sangre de Christo Mountains have the west side as the windward and in some circumstances have the east side as the windward side. When the winds are from an easterly component, upslope slope occurs in the high plains. The best upslope conditions develop when there is a strong area of low pressure in the southern plains. To the north of the low, winds have a strong easterly component. This upslope enhances snowfalls that occur in the lee of the Rockies. An upslope flow causes the air to rise. This results in an increasing of relative humidity (lowers vapor deficits) because the air cools adiabatically as it rises. The dewpoint and temperature convergence upon each other when the air is rising (temperature decreases faster with height than the dewpoint decreases with height in a rising parcel of air). Upslope flow is responsible for phenomena such as mountain summertime convection and upslope enhanced snow.