Microbursts are a very rare but significant problem for aircraft. They typically occur during thunderstorm activity -- but not out of "thin air".

A nice write-up on Wikipedia: http://en.wikipedia.org/wiki/Microburst

Mountain flying requires training. Understanding aircraft performance and mountain winds/weather is the subject of entire books and training programs.

The crash investigation will tell us what happened -- we can only armchair guess. I will say a large number of mountain accidents occur because the pilot is flying UP a box canyon. The terrain rises faster than the aircraft is able to climb. And then the aircraft does not have enough room to turn around because of the close proximity of the canyon walls.