From The New York Times, Olympics 2014: The Science of Snowmaking:
Machines make snow the same way nature does, by freezing water droplets. But they do it a few feet above the ground, rather than in the much colder conditions high in the atmosphere. Snowmaking machines employ a few thermodynamic tricks to help, but at times there is a limit to what physics can do…
…a droplet may not freeze entirely during the few seconds it takes to fall to the ground — what snowmakers call hang time.
“We’re basically making eggs,” Mr. Moulton said — icy shells around still-liquid centers.