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Avalanche Forecast

Archived

Jan 9th, 2025–Jan 10th, 2025

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

Little Yoho.

More wind and some new snow will raise the danger on Friday.

We have noticed some small avalanches running further than expected recently as they gather facetted snow in the track.

Confidence

Moderate

Avalanche Summary

No observations from Little Yoho, but in the neighboring BYK region:

Sunshine snow safety reported a couple small windslabs in lee treeline/alpine terrain that were either skiier triggered or natural in the last 24 hours.

Otherwise, no new avalanches reported, but forecasters did not do a field trip on Thursday.

Snowpack Summary

5-10cm of new snow has been blown into windslabs in the alpine and at treeline. This sits on a layer of facets and surface hoar that is likely to become a bad sliding surface in the future. Below this, the mid-pack is generally strong but a weak crust/facet layer can be found near the ground in shallow snowpack areas. At treeline, average snowpack depths are 120-150 cm. The snowpack here is generally deeper and more consolidated than areas further east in the BYK region.

Weather Summary

A cold front is approaching from the NW. Overnight Thursday, we expect extreme westerly winds followed by up to 5 cm of snow with strong winds on Friday. On Saturday, we expect light snow with winds diminishing to moderate from the NW. Temperatures will remain cool throughout the period.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Avoid exposure to overhead avalanche terrain; avalanches may run surprisingly far.

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.