It really helpd to have drawn it as the tones are quite close together and having studied it in person helped with the painting. (didn't make it easy though!)
The light source was very subtle, being sunset and the light just catching the tops of the mountains. The roofs of the chalets were a lighter tone even without direct light on them.
This was a real study of tonal observation. Fun to paint though and so different from a green landscape!
Last of my snowy paintings till next season... onto spring.