Alpes du Nord
Grandes-Rousses
Day Risk Profile
Avalanche Problems
Wind slab + Persistent weak layers + No distinct problem
4
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
JEUDI SOIR SITUATION AVALANCHEUSE ENCORE CRITIQUE EN ALTITUDE. VENDREDI FORTE INSTABILITE ESSENTIELLEMENT AU PASSAGE DE SKIEURS...
Jeudi soir/en début de nuit
Neige encore et vent de Nord-Ouest, puis les précipitations vont s'atténuer. Avec des cumuls critiques en altitude (dépassant 1m voire 1m50
parfois), on peut s'attendre encore à de grandes avalanches, balayant A steep gully usually adjacent to ridgelines, flanked by rocks, often containing rubble/scree; tends to accumulate drifted snow.EAWS glossary et pentes raides. Celles ci peuvent parfois s'écouler jusqu'en en vallées/près des routes de
moyenne montagne (dépôts plus humides). En haute montagne, la présence de sous couche fragile persistante pourrait faciliter quelques avalanches de très grande ampleur
empruntant des trajectoires peu habituelles...
Vendredi en journée temps plus calme et sec. Fin attendue de la "crue" avalancheuse. Lors de brèves éclaircies coulées ou avalanches poudreuses possibles, près des rochers
notamment. Aux altitudes modestes (sous 1600/1800m environ), la neige est assez humide en profondeur, on peut avoir quelques avalanches en pentes herbeuses, parfois de
fond (glissement au terrain)
Haute montagne encore peu fréquentable vendredi dans la plupart des pentes. Nombreuses plaques encore bien instables, parfois loin des crêtes. Le vent a soufflé en
diverses orientations. Noter qu'en large faces Nord des sous couches fragiles sont enfouies. Une première rupture pourrait entrainer une épaisse et large cassure en
contrebas, entrainant un volume de neige très conséquent...
Plus bas que 1800/2000m environ, les sous couches sont un peu mieux stabilisées, risque de plaques surtout à proximité des crêtes. Le vent le plus récent soufflait du Nord-
Ouest. Vendredi après-midi le vent de Sud se lèverait très localement...
Snowpack & Weather
Snowpack
Situation avalancheuse typique
neige ventée couche fragile persistante
J eudi soir il neige encore, avec 80 cm à 1m20 de neige récente en altitude, des sous couches souvent instables,