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Avalanche Forecast

Archived

Jan 22nd, 2022–Jan 23rd, 2022

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

Northwest Inland.

Strong winds have created stiff wind slabs in the alpine and treeline. 

These wind slabs may be fairly stubborn to human triggering but have the potential to step down to deeper weak layers, resulting in large destructive avalanches.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

Saturday Overnight: Cloud cover increasing, light snow in the early morning. Moderate to strong westerly winds. Freezing level dropping to 500m.  

Sunday: Mainly cloudy, light snowfall. Light to moderate northwest winds. Freezing level rising to 1000m.

Monday: Partially cloudy, trace precipitation. Light to moderate northwest winds. Freezing level rising to 2000m.

Tuesday: Mainly cloudy, light snowfall. Moderate to strong northwest winds. Freezing level around 500m.

Avalanche Summary

On Friday, a large natural avalanche was reported near Smithers on Hudson Bay Mountain, the details can be viewed in this MIN report. The avalanche appears to have initiated as wind slab and stepping down to a buried weak layer, we suspect it was the early January facet layer.

Operators reported another large natural avalanche on Friday afternoon in the Telkwa Range, north of Starr Basin, which also appeared to have run on the early January facet drought layer. These avalanches are an indication that the recent storm and warming temperatures have put enough load on the upper snowpack to 'wake up' this previously dormant layer. 

Snowpack Summary

Earlier in the week, 10-25 cm of new snow was accompanied by strong southwest winds formed wind slabs in lee areas in the alpine and treeline. Westerly winds will continue to redistribute available snow into fresh wind slabs. Below 1200m, this new snow landed on a melt-freeze crust.

Two weak layers may exist in the upper snowpack. First is a layer of surface hoar that may be found around 30 cm deep. To date, this layer has produced avalanches in the centre and north of the region and not the south, though it has been found in the south. Next, a widespread layer of faceted grains is found around 30 to 60 cm deep, which formed during the cold spell in late December and early January. The recent storm has shown the potential for wind slabs to step down to this early January layer. 

In thin snowpack areas, the base of the snowpack is composed of weak faceted grains around various melt-freeze crusts, which are considered dormant at this time.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Watch for areas of hard wind slab on alpine features.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.

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.