score:2
While the main roads in Norway are well maintained in winter and easily navigable for anyone comfortable driving, the experience can be very different than regular summer driving. There are several issues here:
Alternative routes
A less weather-prone route would be to go north on the E39 toward Sognefjorden, cross the fjord by ferry, drive east, and then cross the fjord again by ferry. This route keeps a much lower altitude and I do not think any part of it has substantial risk of being closed save in the most extreme weather.