Weatherwise, it is looking good for Saturday.
There is likely to be some early mist in the Lauterbrunnen valley which will clear to leave full sun later. Meteo Suisse are predicting a maximum temperature of 14°C at Kleine Scheidegg, and a max of 22° in the valley at Lauterbrunnen.
If this changes significantly I will post another message
Edited: 03/09/2012 at 07:59