Snow and Avalanche Report: Week 52-2004

After a long period of dry, stable weather snow made a comeback to the Northern Alps and Pyrenees last weekend and the unstable conditions caught out two groups of ski mountaineers in separate avalanches, one at the Chamrousse and the other in the Aravis. The incident close to the ski resort of la Clusaz in the Aravis left a 20 year old man dead and his father in hospital. Neither were using avalanche transceivers and it took a large team of rescue workers over 90 minutes to recover the body of the young man, a delay that may have proved fatal. Another avalanche covered the Col des Montets road on Sunday morning.

Les Sept Laux earlier today

Backcountry travellers should carry a beacon, probe and shovel when venturing off-piste. It should be remembered that even skiers with beacons get killed by avalanches, the slide at la Rosiere was over 3 meters thick in places. With more fresh snow expected over Christmas there is a continuing avalanche risk remains. Careful route planning, including making a U-turn if conditions are unstable, remain the key to avoiding avalanches.

Northern Alps

After last weekend’s snow the conditions have returned more or less to normal for the season. There was about 80-120 cm of new snow in the Haute-Savoie over the weekend. Another weather front brought snow down to the valley on Wednesday night in the far north of the region and in the Jura. At lower altitudes there is not much of a base which can be pretty hard on skis. Be careful of obstacles hidden in the light snow. There is about half a meter snow depth at 1500 meters and conditions improve rapidly with altitude. The conditions have slowly stabilised over the course of the week although the old base on northern aspects presents a sliding surface for fresh snow. Particular care should be taken on large slopes and in couloirs that have been wind-loaded. The zero isotherm will be around 2300 meters on Friday in the Haute-Savoie rising to 3400 meters to the south in the Isere. There is an inversion layer trapping colder air below 1500 meters in the Isere and this may lead to the formation of surface hoar around this altitude – take care after the next snowfall. This milder weather may provoke some natural avalanche activity (sluffs or full depth avalanches on grass terrain) as the snowpack is warmed on southern aspects. There is a strong north-west wind at altitude which will move some snow around and form new slabs on south-east slopes.

Pyrénées

Last weekend saw the passage of a weather front and a warm episode which brought rain to 2500 meters in the west, 2000 meters to the east. The clear weather on Saturday created an ice crust on the surface of the snow. This formed a sliding surface for subsequent snowfall. The snow level fell progressively to 1200 meters over the cause of Sunday and Monday bringing the total snowfall to 30-40cm in central regions. The snow was accompanied by a lot of wind. This transported snow from ridges onto sheltered slopes and bowls.

The weather is very warm with a temperature inversion trapping colder air in the valleys. A small amount of rain fell on Thursday which humidified the snowpack. The snow level is normal for the season but the warm weather means that the snow is heavy below 2000 meters with a crust between 2000-2500 meters. The recent snow on Monday and Thursday has fallen on a layer with little cohesion and there is a danger of slab avalanches on shady slopes especially above 2000 meters. In the east of the range a strong north-west wind is blowing at altitude. A weather front is expected over the weekend which should bring fresh snow.

References
Météo France issues daily avalanche bulletins for the French Alps, Corsica and Andorra.  You should ideally consult at least the previous 5 days bulletins prior to your trip.

USAF Public Weather Charts

Camp2Camp.com

Henry’s Avalanche Talk publishes a daily translation of the Météo France bulletin for the Savoie area.

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