That looks like a detail set from Details West. They are additional details for a specific type or generation of locomotive. I have several of these, but none that match the parts in your set. The best I can do to help you track it down further is give you the link to their site and suggest you look at their catalog. Details West Website
Since they are not showing all of the components of a kit in the catalog, I suggest you match the snowplow with the individual snowplows and then narrow it down to the kit from there.
Operating the Medford & Salmon Harbor Railroad (M&SH) - "The Harbor Line"