The article noted that the cause of most snow is a living organism, a bacterium, called pseudomonas syringae.
According to the story, "in the last few years, Dr. Sands and other researchers have accumulated evidence that the well-known group of bacteria, long known to live on agricultural crops, are far more widespread and may be part of a little-studied weather ecosystem. The principle is well accepted, but how widespread the phenomenon is remains a matter of debate."
For the full story, see http://www.nytimes.com/2010/05/25/science/25snow.html.
To read more about Sands' work in bio-precipitation, visit this Feb. 29, 2008 story from MSU News:
David Sands, firstname.lastname@example.org, (406) 994-5151