Alpes du Nord
Aravis
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 Indice de risque marqué.
- quelques plaques de fond possibles à toute heure en dessous de 2000 m. Sur pentes très raides, lisses, herbeuses ou vires. Taille 2, voire 3.
- encore des plaques friables à dures dans l'épaisse couche de neige récente. Plaques possibles toutes orientations, surtout NW, N, NE, E, à fortiori au-dessus de 1800/2000 m
et aux endroits propices au transport par le vent. Le vent a soufflé de SW puis S jeudi-vendredi, puis de SE la nuit de vendredi à samedi, puis tourne N samedi en journée.
Cassures d'épaisseur variable 40/90 cm. Taille 2 à 3 (moyenne à grande). Dépôt en blocs.
- facteur aggravant : en versants NW/N/NE/E, au-dessus de 2000 m, possibles départs en cascade : une première avalanche de surface peut solliciter l'ancienne couche fragile
persistante enfouie et décrocher une plaque épaisse en blocs (cassure 1m à 1,50m, taille 3+).
- attention aux corniches formées récemment, grosses et fragiles.
Outlook
Constant avalanche danger
Snowpack & Weather
Snowpack
Situation avalancheuse typique
neige ventée couche fragile persistante
Déclenchements provoqués :
- encore des plaques friables à dures dans l'épaisse couche de neige récente. Plaques possibles toutes orientations, surtout NW, N, NE, E, à fortiori au-dessus de 1800/2000 m
et aux endroits propices au transport par le vent. Le vent a soufflé de SW puis S jeudi-vendredi, puis de SE la nuit de vendredi à samedi, puis tourne N samedi en journée.
Cassures d'épaisseur variable 40/90 cm. Taille 2 à 3 (moyenne à grande). Dépôt en blocs.
- facteur aggravant : en versants NW/N/NE/E, au-dessus de 2000 m, possibles départs en cascade : une première avalanche de surface peut solliciter l'ancienne couche fragile
persistante enfouie et décrocher une plaque épaisse en blocs (cassure 1m à 1,50m, taille 3+).
- attention aux corniches formées récemment, grosses et fragiles.
Départs spontanés :
- quelques plaques de fond possibles à toute heure en dessous de 2000 m. Sur pentes très raides, lisses, herbeuses ou vires. Taille 2, voire 3.
Outlook
km/h 30 km/h 30 km/h
km/h 40 km/h 40 km/h
Tendance du dimanche 15 février
Indice de risque marqué
sque stationnaire ou en légère baisse.
ncore des plaques friables ou dures.