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Avalanche Forecast

Archived

Dec 15th, 2021–Dec 16th, 2021

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

Regions

South Columbia.

 Use extra caution near ridgelines and "thick to thin" areas where the likelihood of triggering avalanches will be greater. The early December layer is starting to produce avalanches that could surprise experienced riders.

Confidence

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

Weather Forecast

Wednesday night: No new snow expected. Wind will be light to moderate from the Southwest. Low of -11 at 1600m.

Thursday: Up to 5cm of new snow with a high of -8 at 1600m. Winds becoming strong from the Northwest in the alpine.

Friday: no new snow expected. Moderate winds from the Northwest shifting to the Southwest. High of -13 at 1600m.

Saturday: a storm arrives bringing up to 15cm of new snow with strong Southwest winds. High of -9 at 1600m.

Avalanche Summary

On Tuesday one skier triggered size 1.5 storm slab was reported on a North aspect at 2200m. This avalanche occurred on the facets above the early December crust. The slab was 35cm thick.

Snowpack Summary

Up to 20cm of low density snow overlies old wind effected surfaces.

The defining feature of the snowpack is a widespread crust that reaches as high as 2400 m and now sits 30-80 cm below the surface. In many places overlying snow is well-bonded to the crust but in others weak faceted grains have been observed growing above it. The faceting is most prominent in the upper treeline where the crust is thinner.

Average snowpack depth at treeline is 200cm.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.