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Avalanche Forecast

Archived

Jan 5th, 2021–Jan 6th, 2021

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

Regions

South Rockies.

Navigate around wind loaded slopes and keep in mind the potential for surprisingly large avalanches due to isolated weak layers.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

A weak front crosses the region on Wednesday then clearing weather into the weekend.

TUESDAY NIGHT: Cloudy, strong southwest wind, temperatures around -8 C.

WEDNESDAY: Isolated flurries throughout the day with up to 5 cm of snow, strong west wind, temperatures around -4 C.

THURSDAY: Cloudy in the morning then clearing in the afternoon, light north wind, temperatures around -6 C.

FRIDAY: Sunny, light wind, temperatures around -6 C.

Avalanche Summary

No new avalanches have been reported since the weekend when there were some small (size 1) human triggered storm slabs and numerous larger (size 2-3) natural storm slab avalanches in alpine and treeline terrain.

Snowpack Summary

Moderate snowfalls and strong southwest wind over the past few days has left hard surfaces and wind slabs in exposed terrain. The upper snowpack consists of several layers of old wind slabs, while the lower snowpack consists of decomposing crusts and weak faceted snow. Some large avalanches were reported on these deeper layers on Dec 23 and 25, but for the most part they have not been reactive over the past few weeks. However, this snowpack structure is always a concern on steep rocky slopes with variable snowpack depths.

Terrain and Travel

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Be aware of the potential for large avalanches due to the presence of 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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.