A morning spent on Union Pacific’s line over Sherman Hill at Dale Junction, Wyoming included a blue sky full of puffy white clouds. While making a nice addition to photo, those clouds cause much angst, constantly threatening to shadow a train. We were cussing the cloud that appeared over the tracks when a 106-car eastbound coal train showed up. Fortunately, the lead unit cleared the shadow, and we were able to salvage an image of the train snaking around the huge s-curve.