Avalanche Forecast
Regions: Birkenhead, Duffey, South Chilcotin, South Coast Inland, Stein, Taseko.
If the wind picks up on Thursday, treat danger as CONSIDERABLE and expect to find reactive wind slabs.
Cold exposure is a major concern for backcountry travelers (read more in this blog).
Confidence
Moderate
Avalanche Summary
Observations have been limited in the past few days. We suspect a widespread natural avalanche cycle occurred with the storm on Tuesday.
Last Saturday, a very large (size 4) avalanche was reported on Joffre shoulder. We suspect it failed on a weak layer of facets or surface hoar overlying a crust at the base of the snowpack.
Looking forward to Thursday, backcountry travelers should watch for evidence of wind transport and be cautious in wind-loaded areas.
Snowpack Summary
20 to 40 cm of recent storm snow was accompanied by strong southwest, switching to northwest winds. New snow overlies wind-affected surfaces and a layer of surface hoar in sheltered areas at treeline and below.
A prominent crust varying in thickness is found at treeline and below, 40 to 80 cm down. In some areas, a layer of preserved surface hoar is found just above the crust.
Another weak layer of facets or surface hoar overlying a crust is found at the base of the snowpack down 80 to 120 cm. This is the suspected failure plane for a few large avalanches in the region that occurred on January 6.
Snowpack depths are 100 to 140 cm at treeline and decrease rapidly below.
Weather Summary
Wednesday Night
Clear periods with isolated flurries. Alpine winds northwest 15 to 30 km/h. Treeline temperatures drop to -20 C.
Thursday
Mainly sunny with isolated flurries. Northerly winds 20 to 40 km/h. Treeline temperature drops to -25 C.
Friday
Sunny with no new snow. Northerly winds 15 to 30 km/h. Treeline temperature drops to -30 C.
Saturday
Sunny with no new snow. Northerly winds 15 to 30 km/h. Treeline temperatures around -20 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Avalanche Problems
Wind Slabs
Winds have shifted to the north, and may be forming fresh wind slabs in a reverse-loading pattern and at lower elevations than is typical.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 2.5
Persistent Slabs
A weak layer found down 80 to 120 cm has been the culprit of recent very large avalanches in the region. This layer may take a few days to adjust to the new snow load. Avoid thin, shallow areas where triggering is more likely.
Aspects: North, North East, North West.
Elevations: Alpine.
Likelihood: Unlikely - Possible
Expected Size: 2 - 4