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Avalanche Forecast

Archived

Dec 16th, 2021–Dec 17th, 2021

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

Regions

South Columbia.

We are reaching a tipping point where triggering large, destructive avalanches will become more likely . Where exactly these large avalanches can be triggered will be hard to predict. Read the forecaster's blog to learn more.

Confidence

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

Weather Forecast

Thursday night: No new snow expected. Moderate Northwest winds in the alpine. Low of -15 at 1600m.

Friday: sunny and no new snow expected. Moderate winds from the Northwest shifting to the Southwest in the evening. High of -15 at 1600m.

Saturday: a storm arrives bringing up to 20cm of new snow with the greatest snowfall in the Monashees. Winds will be strong from the Southwest.. High of -9 at 1600m.

Sunday: some light snow in the morning. Strong Southwest winds in the morning becoming light West in the afternoon. High of -8 at 1600m.

Avalanche Summary

On Tuesday one skier triggered size 1.5 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 10cm 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 above it. The faceting is most prominent in the 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.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

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.

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.