is there any way for the sim to keep snow on the ground after a passing storm? it seems snow disappears and the seasonal textures go back once the weather changes.

No. Snow is created either by the weather listing snow, or in other weather by the seasons.bgl file calling for "hard winter". The file uses a single season map to cover an entire month. To have daily changing snow coverage, would require an application which could update the file daily (or whatever interval). The is daily source data for northern hemisphere available from the US national snow and ice data center, but it typically is a couple days old before it gets uploaded. Conceivably one could devise an app which downloads this data, converts into the correct format for fsx, and installs a new bgl fle on a schedule. I don't know of any data source for the southern hemisphere.scott s..