i don't think you can replace textures on SFXs, so i think you'd just need to edit the anim file so that the snow isn't there... i think you need to delete this from the anim file:
//========================================================== ====================
define snow
{
set hotspot
{
version
{
Visualparticle SFX A Avalanche Snow
}
}
}
//========================================================== ====================
define snowdebris
{
set hotspot
{
version
{
Visualparticle SFX A Avalanche Debris
}
}
}