Some trail runners consider tracking elevation as a vital part in their running routines since they mostly run on either hills or uneven terrains. A barometric altimeter can alert runners when there are changes in elevation, pressure and altitude.  When a trail running watch has this feature, it can track elevation steadily and more accurately compared to a GPS. If your trail running watch cautions you regarding a change in the pressure of the atmosphere, this might mean there will be an incoming storm in your running area.