When reading a National Weather Service forecast discussion during the winter months, we sometimes come across the term "Conditional Symmetric Instability (CSI)". This was true with our latest storm that is winding down today. But what exactly is CSI, how can we diagnose it, and how does it differ from other phenomena that can dump multiple inches of snow in a localized area? CSI involves heavy, banded snow that has a typical duration of 3 to 4 hours. These snow bands have a length anywher