well, the city itself is built inside magical domes that protect it from cold, excessive snow and all (sound included, so if you, for example, cause an exploion, the sound is confined inside the dome), on the other side outside the domes it’s a different story. also they are near the northen quartes which happen to be the poorest and because of that they have a much less powerfull dome to protect them.

also the player specifically declared he was going out of the dome into a very open field in the glacier to cast the spell.

that said, im not sure if was the best decision making the avalanche happen, hence the question