Essentially, this is a transmutation spell that has the same effect for all levels after it's unlocked.  The effect is that it creates a blizzard that lasts for 1 full day.  The air temperature immediately plummets to -10 degrees Celsius and anything caught outside in the storm and/or away from any major heat source (ex. a bonfire) takes 2 cold damage per 5 mins plus the spell casters' wisdom modifier.  The damage scales with every 2 levels, increasing the damage taken and decreasing the time it takes to damage something.  Movement is reduced to 3/4-ths (three-fourths) for anything caught inside the storm.  It's diameter is 6 miles in all directions.  It can be dispelled through sufficient heat cast from a mage capable of concentrating for 5 min in subzero temperatures.  Everything inside the storm is rendered completely invisible to anything outside its diameter.  Even the gods themselves cannot see through the storm.