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Avalanche Forecast

Archived

Feb 13th, 2023–Feb 14th, 2023

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

Regions

Tumbler.

New snow and variable winds will continue to build wind slabs in open terrain features. Seek out sheltered areas to avoid the hazard and enjoy softer snow.

Confidence

Moderate

Avalanche Summary

A helpful MIN report from Saturday in Perry Creek describes active wind slab formation conditions and a solid avoidance strategy. We suspect users who start poking into higher elevations will see evidence of a natural wind slab avalanche cycle.

Looking forward, wind slabs formed by the recent stormy weather are expected to remain reactive to human triggering over the near term.

Snowpack Summary

A few more centimeters of new snow adds to the continued development of wind slabs in lee terrain features in wind-exposed areas by strong to extreme southwest winds. These new wind slabs are building over older wind slabs that may be lingering at treeline and alpine elevations as well as a melt-freeze crust found on sun-exposed slopes and all aspects below 1600m.

Several more crust/facet/surface hoar layers exist in the upper and middle portions of the snowpack. The most concerning persistent weak layer is at the base of the snowpack, composed of large and weak facets formed in November. This layer is widespread and most likely triggerable in steep, rocky alpine terrain.

In general, the snowpack is weaker and shallower in this area than in areas farther west, with an average snowpack depth of around 200 cm at treeline. This makes deep persistent slab problems in thinner snowpack areas here quite a bit more concerning.

Weather Summary

Monday night

Mainly cloudy with convective flurries, 5 to 7 cm accumulation. 20 to 30 km/h southwest winds increasing into the evening, treeline temperatures -10° C dropping overnight.

Tuesday

Cloudy. trace accumulations, 20 km/h northwest winds increasing overnight and switching to the southwest, treeline temperatures -13 °C.

Wednesday

Becoming cloudy, 40 to 50 km/h southwest winds, treeline temperatures around -8 °C.

Thursday

Mix of sun and cloud, 50 to 60 km/h southwest winds, treeline temperatures around -8 °C

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.

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.