This may not be in the same field as snow, but there is a handy little particle tutorial I found a while back on how to make glowing particles.

Something in there which I found might help you is changing the particle type, then adjusting the size of the particle.

Attributes panel>particleshape1>render attributes

Change the particle type to Blobby

There is a button above that which will list extra attributes, hit it.

This will open up an option to change the diameter of the particles.

hopefully this helps