South Fork

Avalanche date/time

Saturday, February 13, 2021 at 15:30

Estimated occurrence time of avalanche

From 24 to 48 hours ago

Number of avalanches in this report

1

The size of avalanche

4

Slab width

320m

Run length

1,558m

Avalanche Character

• Deep persistent slab
• Persistent slab
• Wind slab

Trigger type

Skier

Trigger subtype

Intentional

Start zone aspect

• S

Start zone elevation band

• Alpine

Start zone elevation

2,300m

Start zone incline

34°

Runout zone elevation

1,479m

Weak layer burial date

Friday, February 5, 2021

Weak layer crystal type

• Facets

Crust near weak layer

Yes

Wind exposure

Cross-loaded slope

Vegetation cover

Open slope

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.