Most Americans may not realize it, but we really don’t know with a lot of accuracy how much snow there is sitting in the mountains during winter. We also don’t always have a precise picture of where the snow level is when a storm moves in, or how much will run off when the snow melts. One reason for this is that, in most areas, the weather sensor network in the mountains simply isn’t very dense. Gauges that measure rain and snow are often placed for convenient access.