Touchy Times at Tunnel

Avalanche date/time

Friday, January 29, 2021 at 15:00

Estimated occurrence time of avalanche

From 12 to 24 hours ago

Number of avalanches in this report

1

The size of avalanche

1.5

Slab thickness

25cm

Slab width

40m

Run length

60m

Avalanche Character

• Storm slab

Trigger type

Skier

Trigger subtype

Remote

Remote trigger distance

8m

Start zone aspect

• NE

Start zone elevation

1,850m

Start zone incline

30°

Weak layer burial date

Friday, January 29, 2021

Weak layer crystal type

• Surface hoar

Crust near weak layer

Yes

Wind exposure

Lee slope

Vegetation cover

Open slope

Cautiously poked a little out onto a suspect slope on a slight bench with the aim of digging a pit to help us decide if we were happy to drop into Mercury Bowl. Having previously dropped a small cornice on a similar slope and only seeing slough running with no slab qualities we felt cautiously confident that we weren’t doing a stupid thing. Somewhat inevitably, stomping as I poked out onto this perfect lee slope (where we had observed surface hoar forming not 7 days ago) my last stomp shot a crack 8-10m which then propagated across the slope.

Retreated a little way and dug a pit. With the propagation question answered we did a quick compression test to see how easily it triggered and had a failure at 4 hits from the wrist 25cm down on classic large glassy remnants of surface hoar. There was a further failure at 10 hits from the wrist on what looked like a previous wind slab.

Needless to say we subsequently stuck to south aspects and found great turns with limited amounts of loose dry snow moving around with us.