I see the Avherald report notes a local weather station stating winds were from the North gusting up to 35 knots. Looking at the map provided in the same article showing the police indication of the crash site location, I'd imagine strong potential for lots of curl over, turbulence and downdraft in that area - though that would be something two experienced Swiss pilots would be very well aware of.
A very great shame & tragedy for those involved. The Tante Ju is an iconic aircraft of distinctive looks and sound.