Stanley Headwall wind slab

Banff Yoho & Kootenay National Park

nick.baggaley , Tuesday 12th January, 2021 4:55PM

Headed up to climb at the Suffer Machine complex; didn’t get up anything due to one size 1.5 slab avalanche and other sluffing over our planned route. On approach, noted a prominent, hard wind slab over top of a second, softer slab all resting on a decomposing, faceted mid pack. Crude compression tests showed the upper slab to be very touchy. On the ski out, noted a large amount of sluffing and wind transport all along the Headwall.

Snow conditions were: Crusty, Hard, Wind affected. Weather conditions were: Stormy, Windy, Cloudy. We rode: Alpine slopes. We avoided: Convex slopes. Riding quality was ok.

Avalache Conditions: 30cm + of new snow, or significant drifitng, or rain in the last 48 hours. Whumpfing or drum-like sounds or shooting cracks.

Snowpack

Above tree line, snowpack was variable, from thin with cracking and a 2-5cm thickness wind slab at valley bottom up to approximately 120cm depth with a 1F to P hardness 15cm thick slab over a 4F hardness 10-25cm slab. Facets below. Conducted several crude compression tests, cutting the column with poles. Each yielded one CTE1-2 failure at the slab interface then another CTE3-4 failure below the second slab, both SD. On descent, a third column failed on CTE1 with a break about 40cm down.

Weather

Through the day, sky was overcast with S-1 in the morning, increasing around 8am to S1 with brief periods of S2. Winds picked up around this point as well, from C to L-M SW down valley. Temperatures stayed steady around -5C. Total visible snow from the storm appeared to be about 5cm at tree line on descent.

Avalanche

Observed one avalanche over the Suffer Machine ice around 10am; appeared to be storm slab and size 1.5. Sluffs continued all day over the climb and over the rest of the Headwall on the way out.

Source: Avalanche Canada MIN