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Avalanche Forecast

Archived

Feb 7th, 2023–Feb 8th, 2023

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

Regions

Tumbler.

Watch for reactive wind slabs as you transition into wind-affected terrain. Avoid shallow, rocky areas where the snowpack transitions from thick to thin, and human-triggering slabs is more likely.

Confidence

Low

Avalanche Summary

No new avalanches have been reported, but field information is very limited in this region.

We suspect users who head to the backcountry will see evidence of a natural wind slab avalanche cycle from recent storm snow and strong southwest winds.

Snowpack Summary

+20 cm of new snow in the alpine is being redistributed by southwesterly winds into wind slabs in lees. The recent storm snow sits on previously wind-affected surfaces. Below this, a melt-freeze crust is found on sun-exposed slopes and everywhere below 1600 m.

Several 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 from large and weak facets formed in November. This layer is widespread and most likely problematic in steep, rocky alpine terrain.

In general, the snowpack is weak and shallow in this area with an average snowpack depth of 100 cm at treeline.

Weather Summary

Tuesday Night

Cloud with isolated flurries, 1-3 cm accumulation. Alpine temperatures drop to -8 C. Ridge wind southwest 40-60 km/h. Freezing levels fall to valley bottom.

Wednesday

Mainly cloudy with sunny periods. Ridge wind southwest 60 km/h easing in the afternoon. Alpine temperatures -10 C. Freezing level 800 meters.

Thursday

Mainly cloudy with sunny periods. Moderate ridge wind from the southwest picks up to 50-70 km/h in the evening. Alpine temperatures rise to -2 C. Freezing level rise to 1500m.

Friday

Mainly cloudy with sunny periods. Moderate ridge wind from the southwest picks up to 50-70 km/h in the evening. Alpine temperatures rise to -3 C. Freezing level 1200m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.

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.