Spindrift, as far as snow goes, is defined as fine grained snow being carried by wind or falling. In practice it is usually used to describe the frequent sluffs of snow that fall down steep slopes, gullies, and faces. This iccurs frequently during snowfall or warming, but may occur at other times and for other reasons as well.
The reason very steep slopes have less of a slab avalanche danger is because the snow tends to fall off frequently enough to avoid an accumulation, in the form of spindrift avalanches.
Climbers on steep routes during storms often encounter spindrift at regular intervals. They can even anticipate the next one by keeping an eye on their watch. The intervals will depend on rate of snowfall, winds up above, density of the snow, etc. These frequent spindrift avalanches are rarely dangerous or harmful and few deaths or accidents are atributed to them even though climbing reports of ascents with frequent spindrift are not hard to find.
The photo shows spindrift coming down a rock wall adjacent to a famous ice climb in the Canadian Rockies called the "Weeping Wall". It was taken by Tuan of terragalleria.com on an ice climbing trip with CSAC director Jim Frankenfield in 1994.
The term is also used for ocean spray blown by the wind, and it probably originated with this use.
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