Avalanche Forecast

Archived

Feb 10th, 2022–Feb 11th, 2022

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

Sea To Sky.

Warm and sunny conditions are keeping the danger elevated. Weak cornices and loose wet avalanches should expected during the heat of the afternoon.

The biggest concern remains a weak layer down 30-70 cm which is still capable of producing very large and destructive avalanches.

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

A ridge of high pressure brings very warm and sunny conditions which are expected to persist until the end of Sunday.

Thursday night: Clear, light to moderate N wind , freezing levels 2000-2500 m.

Friday: Sunny, light N wind, freezing levels around 2700 m with an inversion.

Saturday: Sunny, light variable wind, freezing levels near 3000 m with an inversion.

Sunday: A mix of sun and cloud, light to moderate SW wind, freezing levels around 2700 m with an inversion.

Avalanche Summary

On Wednesday, some small natural and skier-triggered loose wet avalanches were observed from steep terrain features on all aspects. An isolated natural cornice failure was also reported.

On Sunday, a near miss occurred on the late-January persistent weak layer in the area of Spectrum Peak, near Rainbow Mountain. At least three large avalanches with 1-2 metre crown fractures were remotely triggered by a group of hikers but no one was caught. Wind loading in the start zone may account for fracture depths that exceed the typical burial depth of the suspected weak layer.

On Saturday in the South Coast Inland region, a fatal size 3 (very large) skier-triggered avalanche was reported in the Duffey Lake area which also failed on the late-January weak layer. This avalanche was triggered in a upper treeline feature on a northeast aspect and showed significant propagation. Click here to read a more detailed report.

This is the same layer that was responsible for a skier triggered size 2.5 avalanche last week on Rainbow mountain. Several smaller skier triggered avalanches on this layer were also reported last week. Most of the avalanche activity on this layer has taken place between 1800 m and 2000 m but it can also be found above and below this elevation band.

Snowpack Summary

Warming temperatures and recent light rain has moistened the surface on all aspects and elevations. Formation of surface crust began Wednesday night and is expected to continue Thursday night with clear skies in the forecast. Prior to the warming and rain, strong winds had caused extensive wind effect and wind slab formation in exposed terrain at higher elevations.

The problematic January crust/facet interface is now buried down 30 to 70 cm. This layer is most prominent between 1800 m and 2000 m, but may be found just above or below this elevation band. It had produced several human and remote triggered avalanches last weekend. Although this layer is widespread, its exact composition and reactivity has significant spatial variability. In sheltered terrain at treeline and just above, surface hoar may sit on the crust which has the potential to further increase the reactivity of this interface.

Terrain and Travel

Be aware of the potential for large avalanches due to the presence of buried weak layers.
Remote triggering is a concern, watch out for adjacent and overhead slopes.
Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
Extra caution is needed around cornices under the current conditions.
Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.