This is from the North Face website:
The Ultra Trail du Mont Blanc has been cancelled 31 miles in due to severe weather. High altitude weather in the mountains is not passable and not safe.
A press conference will be taking place in 1 hour back in Chamonix with the race director. The athletes are returning to Chamonix. Additional information and updates will be provided then, within the next hour or so.
We will update as soon as we have information.