Alpes du Nord
Aravis
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
N Au-dessus de 2000m indice de risque marqué, plus bas indice limité.
Rares petites avalanches dans les falaises ou près des rochers des pentes ensoleillés, sous les éclaircies. Taille 1 (petite).
- rares plaques à vent, d’Direction in which a slope faces as indicated by compass direction of the fall line; i.e. a north slope faces in a northerly direction.EAWS glossary friable, formées dans la neige récente avec le vent de sud-sud-ouest de vendredi. Assez facile à déclencher. Elles se situent essentiellement au-
dessus de 1800/2000 m, à proximité des crêtes. Taille 1 à 2 (petites à moyenne).
Observables : vaguelettes sur la neige de surface, fissures sous les skis, accumulations de neige récente.
- rares plaques sur sous-couche fragile persistante enfouie, dans les versants ouest/nord/est, au-dessus de 1800/2000 m. Difficile à déclencher par un.e skieur.e, mais possible
avalanche en cascade (déclenchement par la plaque à vent décrite ci-dessus). Taille 2 à 3 (moyenne à grande) avec des cassures de 60/80 cm d’épais.
Observables : pas d’indice de surface, test CT, ECT.
Outlook
Increasing avalanche danger
Snowpack & Weather
Snowpack
Situation avalancheuse typique
neige ventée couche fragile persistante
Déclenchements provoqués :
- rares plaques à vent, d’Direction in which a slope faces as indicated by compass direction of the fall line; i.e. a north slope faces in a northerly direction.EAWS glossary friable, formées dans la neige récente avec le vent de sud-sud-ouest de vendredi. Assez facile à déclencher. Elles se situent essentiellement au-
dessus de 1800/2000 m, à proximité des crêtes. Taille 1 à 2 (petites à moyenne).
Observables : vaguelettes sur la neige de surface, fissures sous les skis, accumulations de neige récente.
- rares plaques sur sous-couche fragile persistante enfouie, dans les versants ouest/nord/est, au-dessus de 1800/2000 m. Difficile à déclencher par un.e skieur.e, mais possible
avalanche en cascade (déclenchement par la plaque à vent décrite ci-dessus). Taille 2 à 3 (moyenne à grande) avec des cassures de 60/80 cm d’épais.
Observables : pas d’indice de surface, test CT, ECT.
Départs spontanés :
Rares petites avalanches dans les falaises ou près des rochers des pentes ensoleillés, sous les éclaircies. Taille 1 (petite).
Outlook
m/h 15 km/h 25 km/h
m/h 20 km/h 25 km/h
Tendance du lundi 02 février
Indice de risque marqué
ndi, le vent de sud souffle de plus en plus
rt.
risque en petite hausse, formation de
aques à vent dans la neige récente. Sous-
uche fragile persistante toujours présente.