Horizontal drift of snowflake

Question

I wonder if the random-walk dynamics of falling snowflakes is understood well enough to estimate the likely sideways drift of a single snowflake falling in a windless environment, from its cloud creation to ground touchdown, a sort of expected life-history of a single flake?

For definiteness, say each flake is created in a nimbostratus cloud at height 1km. My guess: sideways drifting is on the order of 100m...?
   
   _{(National Geographic image)}