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Avalanche Forecast

Archived

Dec 15th, 2022–Dec 16th, 2022

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

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Wind slabs can be found in south facing terrain features, and are expected to be bonding poorly to the underlying crust. Buried weak layers may be more reactive as temperatures rise Friday.

Conservative terrain selection and good travel habits are the best strategies to manage the deep persistent slab problem.

Confidence

Moderate

Avalanche Summary

On Wednesday small wet avalanches were reported out of steep and rocky features where solar impact is most significant.

As northerly winds are expected to continue to redistribute snow, natural and rider triggered wind slabs remain possible.

On Monday near Pemberton, a skier-triggered persistent slab avalanche occurred on a northwest aspect in the alpine. The bed surface of this avalanche was reported as a crust with large surface hoar above. Interestingly, this avalanche triggered a size 2 on a nearby slope, which failed on facets and depth hoar near the ground level. This avalanche is a sign pointing toward a developing deep persistent slab problem in this region.

If you head out into the mountains, please share your photos or observations on the Mountain Information Network. Your information helps us understand local conditions!

Snowpack Summary

In exposed terrain at higher elevations, pockets of wind slab sit in wind loaded features while rocks may be exposed on others.

Large surface hoar has been reported on the surface in sheltered areas, with a crust present on solar aspects. Rising temperatures will likely break down surface snow and create a widespread crust below 2000 m once temperatures cool on Friday afternoon.

A layer of weak surface hoar sits buried around 20-40 cm deep. The upper snowpack is generally low density and weak. The mid and lower snowpack consist of crusts and facet layers, with depth hoar observed near the ground, which is very weak and highly uncommon for this region. These layers are the primary concern for this area.

The snowpack is currently weak and shallow for mid December. In deeper areas, snowpack depths only reach 100-130 cm.

Weather Summary

Thursday Night

Clear skies with moderate northerly winds. Freezing level around 500 m.

Friday

Clear skies with an above freezing layer around 1500-2000 m. Moderate northwest winds. Alpine high of 0 °C.

Saturday

Mostly cloudy with 2 cm of snow possible. Light and variable winds expected. Freezing level below valley bottom. Alpine high of -10 °C.

Sunday

Partly cloudy with trace amounts of snow expected. Light and variable winds. Freezing level below valley bottom. Alpine high of -20 °C.

Saturday

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid freshly wind loaded terrain features.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • The best and safest riding will be on slopes that have soft snow without any slab properties.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.