As an action, snow falls in a cylinder twice as big as normal centered on a point within 20 meters. The area is heavily obscured, and exposed flames in the area are doused.

Augment

Sleet Storm. You can expend 1 additional mana so the ground in the area is covered with slick ice, making it difficult terrain. The duration changes to 5 minutes/mana. When a creature enters the spell’s area for the first time on a turn or starts its turn there, it must make a Reflex saving throw.

On a failure, it falls prone.

If a creature starts its turn in spell’s area and is concentrating on a spell, the creature succeed on a Will saving throw against your spell save Difficulty or lose concentration.