Perennial snow in the Scottish mountains
Sites in the Cairngorm mountains
I have walked on the Cairn Gorm - Ben Macdui plateau many times (the first time being in 1983 when the photograph at top left was taken, when I was 12 years old; I have also discovered this photograph which was taken from almost the same spot, a week or so before my photograph was taken), and this area contains the most easily accessible snowfields. Broadly speaking, there are 5 areas on the plateau that can usually be relied upon to hold long-lasting (although not necessarily 'perennial') snow in most years (click on the area name to get my archive of photos of that area):
Other areas that hold long-lasting snow, although perhaps less reliably, are the Cuidhe Crom (or 'crooked wreath') patch at the head of Coire Cas (near the ski slopes and visible widely from the Spey valley), the upper March Burn, upper Coire Mòr and upper Coire Clach nan Taillear (all on the western edge of the plateau above the Lairig Ghru).
There is one other area in the Cairngorms which holds the distinction of having the largest extent of perennial snow in Scotland, and this is Garbh Choire Mòr, south of the summit of Braeriach (click on the area name to get my archive of photos of that area).
I have a strong memory of seeing old snow at the top of the cliffs of Garbh Choire Mòr on the way from Sgòr an Lochain Uaine to Braeriach in September 1994 and being amazed that there was still snow from the previous winter so late in the year (a photograph of Garbh Choire Mòr taken in October 1994 which can be seen here clearly shows the snowpatches reaching up to the corrie lip, which is what I remember seeing). If glaciers were to ever start forming in Scotland again, this would be the first place they would appear.
There are very often three patches in Garbh Choire Mòr that last until the following winter, and these have been named 'Michaelmas Fare', 'Sphinx' and 'Pinnacles' after the rock climbs on the corrie wall above them. The long-lasting snow in Garbh Choire Mòr is sometimes known as the 'Old Man'.