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Avalanche Forecast

Archived

Jan 18th, 2023–Jan 19th, 2023

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

Regions

Microwave-Sinclair, South Bulkley, South Bulkley, Telkwa.

Conditions may be tricker than what meets the eye. Riders could be drawn to sheltered areas around treeline to avoid wind slabs at upper elevation. Buried surface hoar has been active in treeline terrain in recent days, and has the potential to produce large and surprising avalanches. Avoid steep treeline openings and don't let powder hunting draw you into dangerous terrain.

Confidence

Moderate

Avalanche Summary

Earlier in the week, several size 1 to 2 avalanches were reported at Hankin, Ashman, and the Babines. These avalanches were easily triggered by the weight of a rider. They were sliding on a layer of weak, feathery surface hoar crystals, 20 to 30 cm below the snow surface. One of these slabs stepped down to a layer of weak, sugary, facetted crystals that were buried on December 23rd.

Looking forward to Thursday, pockets of wind slabs at upper elevations and persistent slabs in sheltered treeline openings should be your main concern.

Snowpack Summary

Southwest winds are redistributing 20 to 30 cm of low-density surface snow into fresh wind slabs in the alpine and treeline. Yesterday's sun and warm temperatures formed a sun crust on steep solar aspects and on all aspects at lower elevations.

A weak layer of surface hoar formed in early January is now down 30-40 cm. This layer is most prevalent in shaded and sheltered areas at treeline.

A weak layer of facets that formed during the arctic outbreak in December is buried 50 to 80 cm deep. Observations suggest it is fairly widespread, but rounding and gaining strength, and is unlikely to be triggered under the current conditions.

Weather Summary

Wednesday night

Clear periods, isolated flurries. Alpine temperature drop to a low of -8 °C. Ridge wind west 20 km/h gusting to 60 km/h. Freezing level at valley bottom.

Thursday

Mainly cloudy, light flurries. Alpine temperatures reach a high of -4 °C. Ridge wind west 20 km/h gusting to 60 km/h. Freezing level 800 metres.

Friday

Cloudy with snowfall, 2-10 cm accumulation. Alpine temperatures reach a high of -1 °C. Ridge wind southwest 20 km/h gusting to 80 km/h. Freezing level 1500 metres.

Saturday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -4 °C. Ridge wind west 30 km/h gusting to 65 km/h. Freezing level 1100 metres.

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.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.