Half Moon 2.5

Date/heure de l'avalanche

mercredi 12 février 2020 à 17 h 00

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

> 24 à 48 heures

Nombre d'avalanches dans ce rapport

1

Taille de l’avalanche

2.5

Largeur de la plaque

30m

Longueur d'écoulement de l'avalanche

750m

Caractère de l'avalanche

• Plaque profonde et persistante

Versant de la zone de départ

• SO

Bande d'altitude de la zone de départ

• Alpin

Type de cristaux de la couche fragile

• Givre de profondeur

Exposition au vent

Pente chargée latéralement

Couverture forestière

Pente dégagée

Avalanche observed in Half Moon on Thursday Feb 13. Steep alpine SW aspect subject to cross loading with a highly variable snowpack.

The highest crown line looked to be 20-30cm deep and about 30m wide and about 5m away from the ridge top. There were several deeper crowns in the couloir itself which appeared to be up to 1.5m deep and connected across the feature. It appears to have run on basal weaknesses. According to Google Earth it would have ran 750m with debris averaging about 80cm deep spread out over about 350m with the deposit being about 30-40m wide. We called it a 2.5 and aren't sure if it was a Na, Sr or Sa. That South facing ridgetop was about 40-150cm of depth hoar 2 weeks ago when I was last there. There was both sun crust and variable wind slab present on exposed aspects in Half Moon with the sun crust starting to become noticeable about 200m below treeline.

Uncertain if this was natural or skier triggered. That slope is very unlikely to get skied but its high enough on slope that someone traveling to the wisdom tooth may have triggered it.