Avalanche Forecast

Issued: Jan 26th, 2021 4:00PM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada cmortenson, Avalanche Canada

Moderate eastern wind is forecast - which will easily blow around the recent 10-20cm of low density snow from the weekend. Watch for fresh wind slabs or soft slabs at all elevations and remember that these slabs likely sit on a buried surface hoar (and below 1000m a crust).

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

Continued cool temps, outflow easterly wind, and mainly clear conditions with broken skies and the next low arriving Friday.

TUESDAY NIGHT: Mainly clear, light to moderate outflow wind, treeline temperatures around -9 C.

WEDNESDAY: A mix of sun and clouds, light to moderate outflow east wind, treeline temperatures around -9 C.

THURSDAY: Mainly clear, light easterly wind, treeline temperatures around -14 C. A mild alpine temperature inversion builds with warmer alpine temperatures than in the cooler valleys.

FRIDAY: Mainly cloudy with scattered flurries, 5-10 cm new snow, moderate south wind gusting strong late in the day, treeline temperatures around -14 C. A mild alpine temperature inversion persists.

Avalanche Summary

On Tuesday, explosive control in the north produced a few small avalanches in recent snow. Isolated small and large slab avalanches have been reported to have failed on recently buried surface hoar or crust in recent days.  

In the northern regions (e.g. Stewart or Ningunsaw), large explosives were able to trigger a couple of very large avalanches on deep persistent layers near the ground last week. Debris are still evident from the widespread avalanche cycle over a week ago with size 1-3 storm slabs (in the south of the region) and size 3-4 deep persistent slabs (in the north of the region).   

Snowpack Summary

10-20 cm of new snow fell over the weekend, burying a crust below 1000m and surface hoar in sheltered locations at and below treeline. These layers should be investigated anywhere snow fall deposits approach or exceed 20 cm. If reverse eastern wind increases to moderate levels, anticipate fresh wind slabs will form and low density snow will be easily transported into soft slabs or wind slabs. Cold clear temps are perfect for ongoing surface hoar formation and near-surface faceting, which will continue to soften older hard surfaces, develop facets around buried crusts and weaken cornices. 

A total of 100-150 cm of settled snow has fallen in January, which has helped strengthen early season weak layers. Deeper layers appear to have gone inactive in the southern part of the region. However, in the northern part of the region (e.g. Bear Pass, Ningunsaw) there has still been regular avalanche activity on weak snow at the bottom of the snowpack with large loads such as explosives or cornice collapses.

Terrain and Travel

  • Make observations and assess conditions continually as you travel.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Watch your sluff: it may run faster and further than you expect.

Problems

Wind Slabs

An icon showing Wind Slabs

Variable winds shifting to easterly may transport the 10-20 cm of recent low density snow and build fresh wind slabs or soft slabs in immediate lee of windy ridge crests in the alpine and at treeline, cross loaded features and open areas below treeline. These slabs will be particularly reactive anywhere snow overlies buried surface hoar or crust. Elsewhere, loose snow avalanches (sluffs) can be expected in all steep terrain.  

Aspects: North, South, South West, West, North West.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 1.5

Valid until: Jan 27th, 2021 4:00PM