Meteo France have issued the following alert at Thursday 6th December 2012 at 11:18 for the Pyrenees and Northern Alps. The risk is currently Considerable to High for all mountain ranges with a temporary Extreme (5/5) risk during Friday night in parts of the Northern Alps.
A large quantity of snow has fallen in the east of the range since the start of last week. Between Tuesday and Today (Thursday) snowfall has been particuarly heavy. There has been around 60 to 80cm of fresh snow at 1500 meters altitude and the snow pack is now nearly a meter deep. The snowpack has built up rapidly with no stability. The avalanche risk concerns all winter sports enthusiasts and other people going into the mountains be they walkers, skiers or snow shoers. The risk is HIGH (4/5) today and will only decrease slowly on Friday and over the weekend.
Snow cover is excellent, indeed exceptional for the start of December. It is amongst the best starts to winter since 1950. There has been heavy snowfall since Monday afternoon over all of the Northern Alpes. 40 to 60cm of snow has fallen at 1200 meters and over a meter at 1500 meters in many areas of the Haute Savoie and some of the Savoie mountain ranges. The recent snowfall has not had time to stabilize. A single skier or snow shoers can trigger a slab avalanche in many sectors even if the snow looks like powder on the surface. The risk is Considerable (3/5) to High (4/5) over all the French Northern Alps.
Friday will bring heavy, wet snow in the afternoon and the avalanche risk will become High (4/5) in the afternoon. There will be strong winds on ridges and summits from the south-west (gusts to 70 km/h @ 2000m, 110 km/h @ 3000m) Friday morning but these will calm in the afternoon. The snowline will drop from 500 -> 300m during the course of Friday night / Saturday morning. The wind will change to the north on Saturday and strengthen. Around 35cm of fresh snow will fall at 1500m in some areas. Avoid any steep slopes. Risk will pass to Extreme (5/5) during Friday night and road closures are to be anticipated. Keep any travel to a minimum until Saturday morning. On Saturday large slabs are also possible, particuarly all eastern slope aspects (NNE -> SSE) and can be triggered by a single skier.