  In this work, we study the size of the particles involved in a powder snow
avalanche phenomenon. To determine these sizes, we study all the phenomena the
particles have to face before arriving in the "body" of the avalanche. We study
the boundary layer which is at the bottom of the avalanche. We determine, with
the help of experimental data, the range of size of the particles that can be
entrained by the avalanche. We then examine the possibility for these particles
to reach the top of the boundary layer, and so to take part in the avalanche.
Our final result is that the more frequent particles suspended in a powder snow
avalanche have a size lower than 200 micrometers.
