I once read in a mountain flying handbook that in the mountains, winds over 20 to 25 kts at FL100 are a no-go. And in practice, I have found that to be more than enough.
I really like the information that is given by the website
MeteoSchweiz - Wetter
You can buy some specific info on the aviation page. Especially, the GAFOR routes for the various mountain passages are great and really necessary before taking off.
Martin