How a Storm Comes to Mt. Blanc (pic 4)

This is the fourth of a series of pictures taken to illustrate the rapidity of arrival of a major storm over Mt. Blanc. At 15:09, the clouds have invaded the higher Val Veny, covering the entire Trelatete sub-sector (not shown, is on the right of this picture). The wind now is very strong, and I heard the first thunder while taking this picture.