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Avalanche Forecast

Archived

Jan 1st, 2022–Jan 2nd, 2022

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 possible, human triggered probable.
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

South Rockies.

Expect fresh wind slabs forming throughout the day to elevate avalanche danger as the next storm blows in. Also check out the latest Forecasters' Blog for tips on managing the persistent slab problem in this region.

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

Weather Forecast

Saturday night: Partly cloudy. Moderate to strong southwest wind. Alpine temperature around -15 C.

Sunday: A mix of sun and cloud with flurries starting in the afternoon bringing a trace of new snow. Moderate to strong southwest wind. Alpine high of -10.

Monday: Around 5 cm new snow for most areas, up to 20 cm in the west of the region. Moderate southwest wind. High of -5 C.

Tuesday: 5-10 cm new snow. Light southwest wind. High of -15 C.

Avalanche Summary

Wind slabs have been reactive in recent days.

On Friday, explosive control work produced a size 2.5 (large) wind slab avalanche that stepped down to the persistent slab layer on a southeast aspect around treeline.

Wind slabs were touchy on Thursday when natural and remotely triggered size 2 wind slab avalanches were reported on easterly aspects at alpine and treeline elevations.

Explosive control work on Wednesday produced numerous size 3 wind slab avalanches in the alpine on primarily northwest aspects.

Snowpack Summary

Snow surfaces at upper elevations are generally wind affected, the extent of wind effect variable throughout the region with hard slabs especially prevalent in the south.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 50-120 cm. In the past week, we have seen explosive triggered activity on this layer as well as snowpack tests that have shown moderate results. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Terrain and Travel

  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.