Montana

Avalanche date/time

Thursday, January 7, 2021 at 13:45

Number of avalanches in this report

1

The size of avalanche

2

Slab thickness

60cm

Slab width

80m

Run length

250m

Avalanche Character

• Persistent slab
• Wind slab

Trigger type

Skier

Trigger subtype

Accidental

Start zone aspect

• E

Start zone elevation band

• Treeline

Start zone elevation

2,300m

Start zone incline

30°

Runout zone elevation

2,200m

Weak layer burial date

Sunday, December 27, 2020

Weak layer crystal type

• Surface hoar

Wind exposure

Cross-loaded slope

Vegetation cover

Open slope

We observed this avalanche from a distance. There was 1 involvement; initiated from wind affected, steep entrance into a loaded slope. Rider was carried approx. 50m on slab, deployed airbag and was able to ride off of the slab near some large trees. The thickest part of slab appeared to be 70+cm.

We had previously skied an adjacent slope. At the top of that slope (very near to where this slab was initiated) we found hard and resistant but very planar hand shears down 25 and 35cm on stellars over low density snow. We did not observe surface hoar, but failures correlate with Dec 26. We also observed windslab and felt drumming in the snow adjacent to the crown.