Mayeul Aldebert has posted an impressive picture of the cornice on the backside of Mont Pourri that he took the other day. After a snowy and windy winter it is a reminder of this danger that has taken more than a few expert ski tourers and mountaineers. Cornices build over the winter on the lee side of summits and ridges as wind blown snow is deposited. It is often hard to identify the extent of the structure but as a general rule they break much further back than you imagine.
Cornice, Mont Pourri, Savoie [photo: Mayeul Aldebert]
Backcountry travelers should be particularly careful in the spring when there are big temperature differences between night and afternoon when the snow-pack and cornices can become much more unstable. Due to their convex nature the edge can be hard to spot. When you are travelling uphill towards a ridge or summit watch out for changes in the snow to a more compact nature. Never venture past the last visible rock outcrops.
Cornice party, watch it Fido! That's a 1000 meter drop beneath your paws [credit: skitour.fr]