Snow depth
Precipitation & snow total snow depth snow-cover depth
Snow depth measures the thickness of snow already on the ground. It is different from newly fallen snow and from the snow’s water content.
How much is actually lying there?
Depth is measured on a level, representative surface, usually in centimetres. Several measuring points help account for small drifts and bare patches. The drift against the garden fence may be impressive, but it is not a reliable measure of the whole garden.
Three different quantities
- Snow depth: the entire existing cover.
- New-snow depth: snow that has fallen during a specified period.
- Water equivalent: the water left after the snow melts.
Why ten new centimetres may not add ten
An existing snow cover settles under its own weight. Fresh flakes may also melt on warm ground. Ten centimetres of measured new snow therefore need not increase total depth by exactly ten centimetres.
Wind removes snow from exposed areas and deposits it elsewhere. Sunshine, shade and different surfaces add further variation.
Depth is not weight
At the same depth, loose powder contains less water than wet snow. A deeper cover may therefore weigh less than a shallower, soaked one. Centimetres alone cannot reliably determine snow loading on a roof. Model values also simplify local snow distribution.