There are enough people living in the southern part of the US for there to be enough of a market for autonomous vehicles, and that's especially true because I'd bet retired people will be a very large market. They're not going to wait until these cars can safely drive in Alaska before people in California, Arizona, and Florida start buying them.
Besides, the first generation of autonomous cars will look and behave like *any other car* when driven manually. In poor weather (anything beyond light snow or moderate precipitation), the autonomous systems will likely refuse to engage. That doesn't mean an autonomous car won't be useful the rest of the time.
I wonder why people are so convinced that rain and snow will be some insurmountable issue? There are plenty of scanning methods that can penetrate rain or snow fairly easily. A computer doesn't have to rely exclusively on vision, unlike humans.