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Avalanche Forecast

Archived

Dec 19th, 2022–Dec 20th, 2022

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

Regions

Purcells, Dogtooth, East Purcell.

If you're brave enough to endure the cold make sure to keep in mind our buried weak layer.

Cold temperatures and shorter days should play a role in your trip plan.

Confidence

Moderate

Avalanche Summary

At this writing, no new avalanches have been reported in the last 24 hours.

The mid-November layer is still a layer of concern and has the potential to produce large destructive avalanches. Cold temperatures and little snowfall are not likely going to help heal this layer.

Snowpack Summary

In the alpine and at treeline, wind slabs and up to 10 cm of low-density snow make up the top layer of the snowpack. This overlies a variety of surfaces, ranging from hard old wind slabs at upper elevations to soft, unconsolidated facets in sheltered areas.

The main layer of concern is the mid-November layer, which is made up of either surface hoar, facets, or crusts. It is now buried 40 to 80 cm deep. Avalanche activity on this layer has tapered off but it is likely still possible to trigger this layer in isolated terrain features near treeline.

Alpine snowpack distribution is variable, with depths ranging from 70 to 140 cm.

Weather Summary

Monday Night

Clear, no accumulation, 10 km/h west wind, temperature -28 C at 1500 m.

Tuesday

A mix of sun and cloud, trace accumulation, 10 km/h east winds, temperature -25 C at 1500 m.

Wednesday

Sunny with cloudy periods, no accumulation, 15 km/h northeast wind, temperature -32 C at 1500 m.

Thursday

A mix of sun and cloud, no accumulation, 10 km/h southeast winds, -25 to - 30 C at 1500 m..

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.

Problems

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.

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.