Andorra avalanche on 29 Nov kills one; collapse linked to faceted weak layer under wind slab

The avalanche that struck on 29 November in the Clot de les Abelletes area near Pas de la Casa moved an estimated 1,500 cubic metres of snow — roughly equivalent to 1,500 tonnes — and was classified as a D2 event on the European avalanche size scale. The slab, an east‑facing release, had an upper scar of about 30 centimetres and an estimated run of some 180 metres in length with a maximum width of about 50 metres; the toe finished at roughly 2,587 metres after a starting altitude near 2,675 metres, a vertical drop of about 90 metres.

A 32‑year‑old man from Sant Feliu de Pallerols (Garrotxa) was buried by the slide. When located he was in cardiopulmonary arrest and could not be revived. The avalanche involved a party of two people.

Andorra Recerca i Innovació (AR+I) technicians inspected the site on 1 December and carried out a preliminary snow‑pack and meteorological analysis. They identified a weak layer of faceted grains 34–36 centimetres down in the mantle, overlain by a more cohesive slab composed of fine, recently wind‑packed particles; this weak layer is judged to have been the element that failed and triggered the release.

The report reconstructs a sequence of weather events that produced a complex, unstable mantle. Early November snowfalls (5–6 November) were followed by a marked warm spell that created a thick refreeze crust by 14 November, with Saharan dust present at its base. Between 19 and 22 November further snow fell during very low temperatures (a minimum of −15.4 °C was recorded at Envalira, 2,510 m) under strong northwesterly and northerly winds; these conditions favoured the formation of faceted grains. A sudden warming on 23 November produced an additional crust, and subsequent snowfalls with intense winds (24–26 November and later fronts) redistributed and accumulated wind‑packed snow on lee slopes, creating areas of surplus snow and visible erosion in the cirque.

Technicians were able to reach the avalanche’s toe without major difficulty; access to the scar required ascending toward Pic Blanc and approaching as close as conditions allowed. The AR+I study frames the accident as the collapse of a transformed weak layer within an otherwise cohesive, wind‑affected slab, in a locality where recent irregular snowfall and strong winds had produced variable and excess snow loading.