Whoops! Must put this thread on 'tracking' mode...
Let me give you the answer that my good friend and colleague
Adam Watson gave in another thread on Winterhighland:
"Of course none of us can be sure about anything until the main spring thaw has exposed the locations and sizes of snow wreaths. That's an exciting sight every year, but I think will be more anticipated in 2010 than usual <...> but since mid December I've thought 2010 is unlikely to be a top year for autumn snowbeds. Firefly and I agreed this when he came to Deeside and the Mearns in late December.
First, a long snowy winter is not necessarily conducive to unusually many late snowbeds. This is particularly the case if most snowfall comes on north winds, or easterly such as this winter (predominantly NE and SE, though there has been some substantial snowfall and drifting from NW and other directions). Firefly makes this point well. Most long-lying snowbeds face NE, to a lesser extent E or SE. The deepest corries and other holes face these directions, associated with glaciers in the last glaciation occurring on these aspects and forming these corries and holes. Deep holes that face NE are shaded from the sun for much of the day, and crucially in the afternoon, when the sun has warmed air to its maximum for the day. Although many hollows and some corries face W or SW or NW, they are fewer and usually much shallower. Their topography affords little shade from sun during the warm part of the day, and snow depth cannot be massive because the hollow is too shallow.
In 1996 most snowfalls came from SE and there were huge wreaths in June and July on NW-facing slopes, but the deep NE-facing holes had less than usual, and in the end no patches survived. One of the last patches was at the March Burn on Ben Macdui, huge in July, but of course it faces west and melted rapidly in warm sunshine in afternoons. Braemar had 60 days with snow in 1958-59, well above its winter average, and it was a snowy winter in Glen Esk of Angus, but I recall extremely rapid loss of snow by sublimation in Glen Esk, and in the end no snowbeds survived in Scotland, the first time I'd seen this.
I think Doug makes a very good point about the lack of wind this winter. Although much drifting occurred with the recent storm, earlier snowfalls were marked by little wind and remarkably uniform undrifted powder. Although much of the earlier snowfalls were later shifted by wind, this is not like an initial storm, because much of the blowing snow has been lost by sublimation.
As Firefly points out, a top year for autumn snowbeds ideally requires deep Atlantic depressions with heavy precipitation on gales from SW or nearby such as S and W and NW, when much of the precipitation on lowland is rain or sleet. This is especially so for Lochaber, but important everywhere. We may of course yet see it in March or April or May, but the long-range forecast of a strong anticyclone till at least 20 March is good for skiers and climbers, but not for long-lying snow patches!
The Met Office say this is the coldest snowiest winter in Scotland since 1962-63, and that accords with my experience in NE Scotland. The snowfalls of 62-63 came on predominantly SE winds. Have a look at Firefly's archive of snow-patch photos, search for 1963, and you should see my photos of Garbh Choire Mor in late September, with 4 smallish patches. In the end, only three of them survived."
The thread this was taken from in WH is here.
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firefly, on 07 December 2009 - 09:54 , said:
