It's a course preparation matter. You need a groomed surface and fences to line the course and since it's ski racing, poles in the ground to mark the actual course

Lake Tahoe just got close to 10 feet of snowfall, meaning the courses were presumably buried and have to basically be remade. It's not "they got some fresh snow" it's "there's so much snow resorts are closing for a couple days to dig themselves out of it to resume lift operations"