I get a chuckle out of these threads. Humans are _unbelievably_ bad at driving in the snow. If the only thing a self-driving car does in a whiteout snow storm is come to a halt, it will already be dramatically safer than human drivers. You can just hard-wire the car to not do stupid things. Taking human judgement out of the loop has many wonderful outcomes.
This is a bit aside from your main point, but stopping on a road in a whiteout snow storm is _incredibly_ dangerous due to the cars behind you being unable to see you until it is much too late to stop. I grew up driving two-lane highways in Alaska with frequent semi traffic, several times in blizzard conditions (to the point where the only way to follow the road was to drive on the flat part of the just-fallen snow). You could pull over to the side of the road, but you may not be able to get back on the road depending on your vehicle and the snow level (and in remote, cold areas this may be deadly itself).
You could say "just don't drive in blizzards", but on a long drive you may often end up in a blizzard when you started in clear weather. Frequently this happens in areas where there are no safe places to stop for miles.
I'm not an expert on self-driving car sensors, but it's not hard to imagine that they could be made much less weather-dependent than the human eye. Driving through blizzard conditions is incredibly disorienting and terrifying, so the potential of better-than-vision detection of roads and traffic is IMO the most promising way for self-driving cars to handle snowy conditions.
Potentially, a self-driving car (or even Google Maps nav and a regular driver) would not have this problem - it would simply not drive itself into a situation where it's both in heavy snow and a place that's not safe to stop. I've had a few times in California where I started a long drive in sun and warm weather and ended up stuck in a snow-storm mid-drive (hello Sierra passes)... it would have been nice if either my car or my map software warned me this was likely before we set off.
Autonomous cars would be coming from a variety of vendors each with its own algorithms. It's not even guaranteed that they would communicate with each other to arbitrate strategy under adverse conditions.
It's not as if human drivers do, either. The closest we've come is Waze, which would a trivial data set for an autonomous car to both utilize and supplement.
https://youtu.be/rhZCyQ3emQg?t=121