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Avalanche Forecast

Archived

Dec 3rd, 2022–Dec 4th, 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.

Watch for lingering wind slab at higher elevations where winds have varied in direction. Small avalanches have the potential to trigger deeper weak layers. Assess conditions as you travel and gain information.

Confidence

Moderate

Avalanche Summary

Observations are currently very limited. A small slab avalanche was observed Thursday around 2000 m on a steep, south-facing road bank. It failed and propagated on the sugary, faceted layers snowpack, 25 cm deep.

We have very few eyes out there. If you do get out please consider reporting in the MIN.

Snowpack Summary

The upper snowpack has been redistributed by variable winds into wind slabs that can be found on many aspects, these overlie a generally weak, sugary, facetted lower snowpack. In exposed terrain slopes may have been scoured back significantly. A buried layer of surface hoar sits 25-45 cm deep and remains a layer of concern.

The overall height of snow is highly variable throughout the region with around 70-150 cm in the alpine.

Weather Summary

Saturday Night

Mostly clear skies overnight. Light to moderate westerly winds. No snowfall expected.

Sunday

Clear skies, light westerly winds. No snowfall expected. Alpine high of -12.

Monday

Mostly sunny with scattered cloud, moderate westerly winds and alpine temperatures around -15 C. No snowfall expected.

Tuesday

A mix of sun and cloud with isolated flurries bringing trace amounts. Moderate to strong westerly winds. Alpine high of -17.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Carefully evaluate steep lines for wind slabs.
  • Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.

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.