Here are some snow buildup projects to examine.
Simple Snow Buildup (Free if you want, just enter 0)
Snow Buildup, Melt, and Drift
Maybe with a population could be useful to render a depth passh from an ortho camera and use it after smoothing.
As soon as i understand how to output render elements, i'll give it a try!
Nice project Jordan !
I tried to buy your project but the Gumroad payment with Paypal was not functional !
Will try later !
Thanks for the free version !