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Avalanche Forecast

Archived

Jan 21st, 2020–Jan 22nd, 2020

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

Regions

South Coast Inland.

Watch for slopes where thick deposits of new snow have accumulated, especially in wind-affected terrain.

Confidence

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

Weather Forecast

TUESDAY NIGHT: 20-30 cm of snow in the southern part of the region and 5-15 cm in the northern part of the region, moderate wind from the southwest, alpine temperatures drop to -5 C.

WEDNESDAY: Cloudy with isolated flurries and up to 10 cm of snow, light to moderate wind from the southwest, alpine high temperatures around -3 C.

THURSDAY: 5-15 cm of snow above 1600 m (rain below), strong wind from the southwest, alpine high temperatures around -1 C.

FRIDAY: Another 5-15 cm of snow, moderate wind from the southwest, alpine high temperatures around -3 C.

Avalanche Summary

Recent storms resulted in several small (size 1) naturally-triggered slab avalanches in the northern part of the region on Sunday and Monday. Wet loose avalanches were reported around the Coquihalla over the same period.

Snowpack Summary

New snow is accumulating above wet and crusty interfaces after warm temperatures reached treeline elevations on Sunday. With strong southwest wind, expect scoured windward slopes in the alpine and thick wind slab deposits in lee terrain.

There are currently no concerns about deep weaknesses in the snowpack near Coquihalla summit and elsewhere in the south of the region. In the northern half of the region (e.g. Duffey, Hurley), there are several layers of concern. One is a weak layer of surface hoar buried about 100 cm deep that professionals are tracking at treeline and below on shaded aspects in sheltered areas. The other is weak faceted grains and crusts near the bottom of the snowpack, that is most likely to be triggered in shallow rocky start zones.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.