South Fork

Date/heure de l'avalanche

samedi 13 février 2021 à 15 h 30

Estimation de l'heure d’occurrence de l’avalanche

> 24 à 48 heures

Nombre d'avalanches dans ce rapport

1

Taille de l’avalanche

4

Largeur de la plaque

320m

Longueur d'écoulement de l'avalanche

1 558m

Caractère de l'avalanche

• Plaque profonde et persistante
• Plaque persistante
• Plaque à vent

Type d'élément déclencheur

Skieur

Sous-type d'élément déclencheur

Intentionnel

Versant de la zone de départ

• S

Bande d'altitude de la zone de départ

• Alpin

Altitude de la zone de départ

2 300m

Inclinaison de la zone de départ

34°

Altitude de la zone de dépôt

1 479m

Date d'ensevelissement de la couche fragile

vendredi 5 février 2021

Type de cristaux de la couche fragile

• Grains à faces planes

Croûte près d'une couche fragile

Oui

Exposition au vent

Pente chargée latéralement

Couverture forestière

Pente dégagée

One rider watched from a safe point on the ridge as the other cautiously ski cut the top of a large, south aspect ,concave bowl. We expected a smallish wind slab might release, but the outcome was far greater. He was able to find the sweet spot and the wind slab cracked in weak, shallow snow near some krumholtz. The rider stopped and watched as the bowl crowned and spiderwebbed 10 metres below, zippering 320 metres across the concave slope. We watched in awe as the entire bowl roared down the mountain, stepping down and cleaning out all the buried persistent weak layers present in the snowpack. The avalanche widened the trim line in the path by 5-10 metres for the final 500 metres ,running full path and uphill on the opposing side of the valley.

Once we collected our selves we crossed the bed surface and rode a treed ridge to valley bottom. The bed surface near the crown was facets on crust.

We made a mistake stepping out too far for the uncertainty of the conditions.

Had either of us been caught, it is extremely unlikely we would have survived.

Fortunately our habits and actions mitigated what happened, and we were lucky.