The Bug:

Powder snow placed above farmland or dirt paths does not convert the farmland into dirt.

Steps to Reproduce:

• Place some farmland near water (This is to prevent the farmland from naturally converting into dirt) or some dirt paths.
• Place some powder snow above it.
  →  Notice how the farmland/dirt path does not convert to dirt, despite powder snow being placed above it.

Information:

This could be intentional.