A repost from the Beeb.   I saw snow on Ben Nevis when I hiked the Great Glen in 1993.  “Neve” snow is the snow that lasts from year to year, and can form a positive feedback loop as it keeps the surrounding area cooler and more reflective (higher albedo), which can lead to the creation of more snow, etc.   I haven’t looked at the relative precipitation levels in Scotland, but it’s fair to say they’re always rainy.   Joking aside, there might be scenarios where warmer temperatures bring disproportionately more snow, which means you get this sort of accumulation.

https://www.bbc.com/news/uk-scotland-highlands-islands-37020327