Rainfall snow depth equivalent

Estimated accumulations from weather radar

I had always thought that one inch of rain approximated to ten inches of snow, or in metric units that’s 25.4 mm of rain equals 25.4 cm of snow a ratio of 1:10. That ratio is very much dependent on the air temperature at the time the snow is falling of course, and the colder it is the fluffier the snow and the greater the depth. I had never given it much thought until this morning when I was looking at yesterday’s rainfall accumulations from weather radar. Wittering was the snowiest place yesterday with their AWS reporting a maximum depth of snow of 18 cm yesterday at 20 UTC. The total rainfall equivalent yesterday for Wittering was 18.4 mm which just goes to show that the old 1:10 approximation for snow falling with a temperature close to zero is pretty accurate.

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