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Avalanche Forecast

Archived

Jan 10th, 2024–Jan 11th, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, 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.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.