A ball of snow flashes from your pointing finger to a point you choose within range and then blossoms with a frigid howl into an icy cover. Each creature in a 30-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 3d6 cold damage on a failed save, or half as much damage on a successful one. A creature that fails the save is petrified, as it is covered in a thick sheet of ice. If any creature covered in this ice takes more than 6 points of fire damage, the ice melts and the condition ends on the creature. The ice is magic, and wont melt under non-magical flames. 

The area becomes difficult terrain, and creatures must make a Dexterity saving throw or be nocked prone if they try to move over the sheet of ice. Any class ability that exempts creatures from making saving throws against the casters spells (like the Evocation Wizards Sculpt Spells ability or a Sorcerers Careful Spell metamagic) may exempt a 5 ft. section from the spells area of effect instead of a creature.

The ice spreads around corners. It covers objects in the area that aren't being worn or carried. 

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the area of effect increases by 10 ft.