Alpes du Nord
Mont-Blanc
Day Risk Profile
Avalanche Problems
Wind slab + Persistent weak layers + No distinct problem
3
Field notes
Wind slab
Look for fresh snow deposits on Slope facing downwind/ wind sheltered aspect. Snow deposits can attain several times average snow depth.EAWS glossary, in Usually a steep, elongated, eroded trench; typically prone to snowdrift accumulation.EAWS glossary and Rounded or elongated concavity; typically tending to accumulate snowdrift.EAWS glossary, and behind ridgelines and abrupt changes in terrain — these are where the wind has loaded the snow into slabs that are easy to trigger. Recent avalanches, shooting cracks under your weight, and Distinctive noise (resembling a “whumpf” sound) occurring when a weak layer beneath a slab collapses. The air of the weak layer is forced outside the snowpack, with the resulting whumpf sound being heard. The sound usually indicates an unstable situation and can be accompanied by surface cracking. A whumpf is a clear avalanche alert.EAWS glossary sounds are clear confirmations of the problem. The safest move is to avoid wind-loaded terrain entirely. NB wind signs alone don't always mean an avalanche problem exists, and the age of drifted snow is hard to judge.
Persistent weak layers
Persistent Snowpack layer in which the crystals are poorly bonded and the layer has the potential to fail. Typical crystals in dry weak layers causing avalanches are : precipitation particles; surface hoar; faceted crystals; hollow crystals; graupel. Generally >1mm in size, loose grains with few bonds Wet weak layers can be formed by all snow crystal/grain types.EAWS glossary are very challenging to recognise. Distinctive noise (resembling a “whumpf” sound) occurring when a weak layer beneath a slab collapses. The air of the weak layer is forced outside the snowpack, with the resulting whumpf sound being heard. The sound usually indicates an unstable situation and can be accompanied by surface cracking. A whumpf is a clear avalanche alert.EAWS glossary sounds and shooting cracks are typical when present, but you can have a serious weak layer with no warning signs at the surface. Knowledge of how the Snow deposited on the ground in a multiplicity of layers.EAWS glossary has evolved is essential. SLF's travel advice is direct: travel conservatively, avoid terrain where the consequences of being caught are large, and treat the history of weather and snow as more important than what you can see today. Read the full bulletin.
No distinct problem
SLF uses this label when no single problem dominates the assessment, often on lower-danger days. It doesn't mean conditions are safe: any avalanche type is still possible, and normal caution applies. On stable days this is usually a signal to enjoy the mountains with general awareness; on less-stable days where the assessment is still inconclusive, it's a signal to be cautious specifically because there's no clear pattern to follow.
Avalanche Activity
INSTABILITÉS SURTOUT DANS LES VERSANTS OMBRAGÉS
Rares plaques de fond de jour comme de nuit sur les pentes herbeuses ou les dalles rocheuses, sous 2200 m, surtout dans les versants ensoleillés. Taille 2 (moyenne).
*rares plaques reposant sur une couche fragile persistante vers 2000/2800 m, dans les versants ombragés (E/N/W). Difficile à déclencher. Tailles 2 à 3 (moyenne à grande) avec
des cassures jusqu’à 1 m.
- plaques à vent dans la neige récente. Facile à déclencher. Souvent près des crêtes, au-dessus de 1800 m. Tailles 1 à 2 (petite à moyenne). Formées par le Foehn de ces derniers
jours.
Observables : transport de neige par le vent, vaguelettes, accumulations de neige, fissures devant les skis.
Outlook
Constant avalanche danger
Snowpack & Weather
Snowpack
Situation avalancheuse typique
couche fragile persistante neige ventée
Déclenchements provoqués :
*rares plaques reposant sur une couche fragile persistante vers 2000/2800 m, dans les versants ombragés (E/N/W). Difficile à déclencher. Tailles 2 à 3 (moyenne à grande) avec
des cassures jusqu’à 1 m.
- plaques à vent dans la neige récente. Facile à déclencher. Souvent près des crêtes, au-dessus de 1800 m. Tailles 1 à 2 (petite à moyenne). Formées par le Foehn de ces derniers
jours.
Observables : transport de neige par le vent, vaguelettes, accumulations de neige, fissures devant les skis.
Départs spontanés :
Rares plaques de fond de jour comme de nuit sur les pentes herbeuses ou les dalles rocheuses, sous 2200 m, surtout dans les versants ensoleillés. Taille 2 (moyenne).
Outlook
m/h 10 km/h 15 km/h
km/h 20 km/h 60 km/h
Tendance du samedi 06 décembre
Indice de risque marqué
medi, nuageux avec de faibles chutes de
ige toute la journée. Vent SW 30/50 km/h.
mite pluie neige vers 1800 m. 5/15 cm de
ige au-dessus de 2200 m.
formation de nouvelles plaques dans la
ige fraîche.