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Avalanche Forecast

Archived

Mar 3rd, 2020–Mar 4th, 2020

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

Cariboos.

Wind slabs have been reactive lately and will continue to build with light overnight snowfall and strong winds. Fresh snow will be especially sensitive if the sun comes out Wednesday.

Confidence

Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

Tuesday night: 5-10 cm new snow. Strong west wind. Freezing level dropping to valley bottom.

Wednesday: Mix of sun and cloud with isolated flurries. Moderate northwest wind. Freezing level valley bottom.

Thursday: 5-10 cm new snow. Strong southwest wind. Freezing level 1500 m.

Friday: 10-20 cm new snow. Light southwest wind. Freezing level 1000 m.

Avalanche Summary

On Monday and Tuesday several large natural wind slabs size 2-3 were observed on northeast to southeast aspects in the alpine. Some were triggered by cornices failures. 

Over the last few days, persistent slab avalanches were reported, running on the surface hoar layer. Skier triggered size 1-2 on north to east aspects in the alpine, and natural size 2-3 in steep alpine terrain with a few size 2 observed below treeline. Natural wind and storm slabs size 1.5-3 were observed on north to east aspects in the alpine on Sunday.

Snowpack Summary

Incremental snowfall and strong winds continue to build deep pockets of fresh wind slab in the alpine and open areas at treeline.

A weak layer of widespread surface hoar sits 60-90 cm deep. There is uncertainty about the distribution and reactivity of this layer especially in the north of the region. Read more about surface hoar on our forecaster blog! 

The early February melt-freeze crust down 80-120 cm has not been associated with avalanche activity but still gives results in snowpack tests.

Terrain and Travel

  • 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.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Brief periods of sun could quickly initiate natural avalanche activity.

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.