You conjure a swirling storm of icy magic centered on a point you can see. The area becomes heavily obscured, and the ground is covered in slick, arcane-infused ice. When the storm appears, each creature in the area must make a Dexterity saving throw or fall prone and take 3d6 cold damage. Creatures that enter the area or start their turn there must also make the saving throw.   The storm extinguishes flames and renders the ground difficult terrain. A creature concentrating on a spell in the area must succeed on a Constitution saving throw to maintain concentration.