It’s been quite a cold start to the month of May 2019 and their is a decent snow cover down to 2500 feet on Ben Wyvis in recent days. That’s not so surprising as the 1000-500 hPa partial thickness has been sub 528 Dm for the last week at Lerwick. I think this probably makes it one of the longest such cold spells in the entire winter-spring period of 2018-19. It’s been a long time since I saw snow falling in either October or May but it happened in a year with a comparatively mild winter.
Another useful guide to just how cold it’s been in the Scottish mountains is the thermograph from the SIESAWS on Cairngorm.