Snowflake Science: How It Snows for Days in the Arctic

For snow to form, there has to be stuff in the atmosphere ¬— microbes, specks of dust — for water molecules to freeze on and then form ice crystals. But in the Arctic, where the atmosphere is very clean, it can sometimes paradoxically snow for days.



via LiveScience.com http://www.livescience.com/42206-arctic-snow-atmospheric-particles.html