I also live in a US state where snow is the norm for that amount of time. I would argue "comfortable" is not safe and also, ultimately, not Level 5. There are some situations that are just not passable while maintaining safety. That's the reality and you are making risk choices that are subjective which cannot be understood by the AV. But we shouldn't assume because there will always be situations where a car will refuse to drive because of conditions that it's all for nothing.
I agree that I think it'll get there. But, like air travel there are limits and limits ground flights. When we drive a car we don't have a rigid pre-drive checklist, people in ATC watching out for weather and other aircraft, and then a company behind the scenes making the call on risk of life, money and brand reputation. Sure, weather is probably the hardest to deal with in knowing ahead of time if the trip can be completed with 100% success rate. I think the bigger problem is that as cars start to drive themselves, for people with little drive time throwing those people in the mix to take over will result in a very bad outcome. I have over 20 years of driving in ice and snow and still run across situations that are challenging or catch me off guard. But... What about that 17 year old who's car just told them to take over and they've never had to deal with driving in a storm ever? As we stop the task we lose the skill. Ultimately I feel that's the bigger issue holding things back until the manufacturers can get to Level 5.