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Avalanche Forecast

Archived

Feb 13th, 2023–Feb 14th, 2023

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

Regions

North Rockies, Kakwa, McGregor, Pine Pass.

Continued snowfall through Monday evening coupled with moderate variable winds will continue to form fresh and reactive wind slabs primed for human triggering on steep slopes across the region.

Confidence

Moderate

Avalanche Summary

Recent observations have shown a trend away from the very large persistent slab and deep persistent slab avalanches and toward surface instabilities such as wind slabs. We expect this trend to continue, however, the basal snowpack remains questionable and should still figure into terrain selection around steep features with shallow or variable snowpack areas where these layers may be more easily triggered by a person or machine as well as large wind slab or cornice releases.

Snowpack Summary

Roughly 10 to 15 cm of new snow, coupled with winds shifting to the northwest may build new wind slabs on south and east-facing terrain from reverse loading. These new wind slabs will be developing over variable surfaces of soft snow in sheltered terrain and old wind slabs in open terrain features.

Several strengthening crust/facet/surface hoar layers can still be found in the upper and middle portions of the snowpack. The most concerning persistent weak layer, however, is at the base of the snowpack and composed of large and weak facets formed in November. This layer is strengthening slowly as well, remaining most likely to be triggered in thin, rocky alpine and upper treeline terrain.

Weather Summary

Monday night

Cloudy with scattered flurries bringing another 5-10 cm of new snow. Northwest winds 20 to 30 km/h. Treeline temperatures -11°C.

Tuesday

Cloudy, clearing in the afternoon, 15 to 20 km/h northwest winds switching to the southwest and increasing throughout the day. Treeline temperatures -12 °C

Wednesday

Increasing cloud with isolated flurries, 20 to 30 km/h southwest winds, treeline temperatures -8 °C.

Thursday

Cloudy with 5 to 7 cm of new snow, 10 to 20 km/h southwest winds, treeline temperatures -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use increased caution at all elevations. Storm snow is forming touchy slabs.
  • Use careful route-finding and stick to moderate slope angles with low consequences.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.