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Avalanche Forecast

Archived

Jan 23rd, 2022–Jan 24th, 2022

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

Regions

South Rockies.

The danger ratings don't tell the whole story. Uncertainty regarding the Deep Persistent Slab problem would have me avoiding any large or committing features. 

Confidence

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast. We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

Sunday Night: Scattered clouds. No new snow expected. Light to moderate northwest wind. Freezing levels drop to near valley bottom. 

Monday: Mostly cloudy. 0-4 cm of snow expected. Light northwest wind with periods of strong northeast at higher elevations. Freezing levels rise to around 1000 m. Alpine low around -7 C.

Tuesday: Scattered clouds. No new snow expected. Light winds in the morning trending to moderate from the west in the afternoon, and strong northwest at higher elevations. Freezing levels drop to valley bottom overnight, rise back to 1000 m by the afternoon.

Wednesday: Scattered clouds. No new snow expected. Light west wind trending to extreme northwest at higher elevations. Freezing levels near valley bottom overnight, rising to 1000 m by the afternoon. 

Avalanche Summary

On Saturday, neighbouring Waterton National Park reported a few natural windslab avalanches to size 2 on solar aspects in the alpine. 

A Mountain Information Network (MIN) post from west of Elkford reported a large avalanche that looks to be a couple of days old due to snow on top of the debris. It failed below some cliffs in the alpine and ran into flatter terrain below. See here for more details.

On Friday morning the field team reported four new wind slabs size 2.5 to size 3 that looked to fail on the (re-loaded) early December interface in the Crowsnest North. One of these appeared to be triggered by a cornice fall.

Snowpack Summary

Moderate to strong winds continue to affect the surface snow, building fresh, thin windslab. Expect to find a thin suncrust on solar aspects, especially in the high alpine, where temperatures may have gotten above zero over the weekend. 

The upper snowpack is variable throughout the region with a melt-freeze crust found 10-20 cm down (aspect and elevation dependant, maybe even on the surface in windward terrain). This crust is less likely to exist above 2000 m. 

One common theme throughout the region is that the mid-pack is well settled above the deeper December crust/facet interface which is currently the primary concern in the snowpack.

The early December crust is now generally down 80-150 cm. This layer is found widespread through the region but with varying test results. Recent snowpack tests have shown more reactivity in shallower snowpack areas as well as the potential for step down avalanches. This indicates that there is potential to trigger this weak layer from a thin spot which may propagate to a thicker slab within the snowpack, creating a very large avalanche. 

Daytime warming, solar radiation, and cornice fall could all play a role in triggering deep persistent slabs.

Terrain and Travel

  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avoid terrain traps where the consequence of any avalanche could be serious.

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.