HHbomb -- I can post my 3ds max scene (2015 version), if you want
I use clone plugin -
http://www.itoosoft.com/freeplugins/clone.php , 25 clones, 300x300 m, 20 cm spacing, path tracing, diffuse depth - 8. Clouds material (for the animation) - gamma 0.51, contrast 140, octaves 9, omega 0,786, scale 500, 100, 800.
Yes I know, maybe this clouds aren't really, really realistic, but for me, close enough, and are fully animatable, velocity, density, may be illuminated, for example, by a lightning bolt etc.
