I know, believe me. But right now, can walk up to Frutigen from west, north and east without any problem and then you face a huge mountain range. I just thought it would feel more like approaching the Alps if there were some smaller impassable mountain ranges before you stand right in front of the massive ones.
Between Martigny and Aosta would be another one. And in theory between Martigny and Sallanches, but they decided not to put impassable mountains between Monthey and Faucigny (yet).
I think movement should be stopped in every province with severe winter, but only during the severe snow of course. But mountain locations (in the Alps) should be much more likely to experience severe snowfall. The Alpine passes shown by Lord_Telchar should not be crossable in normal winters either. But honestly I'm not sure if a more granular system like this is in scope for the game or even the release version.