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Avalanche Forecast

Archived

Dec 2nd, 2022–Dec 3rd, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells, Dogtooth, East Purcell.

Snowpack is generally weak, thin, and sugary. The main avalanche hazard exists in areas where a cohesive slab has formed on top of a weak lower snowpack.

Confidence

Moderate

Avalanche Summary

A small (size 1) slab avalanche was observed Thursday in the upper below treeline region (~2000 m), on a steep, south-facing road bank. It failed and propagated on the sugary, faceted lower snowpack, down 25 cm from the surface.

Snowpack Summary

The surface snow continues to dry out (facet) with the current cold temperatures and is being redistributed by variable winds. In the alpine and treeline, much of the wind-exposed terrain has been scoured of snow. In deeper snowpack (loaded) areas, cohesive wind slabs may exist and generally overlie a weak, sugary, facetted lower snowpack.

The overall height of snow is highly variable throughout the region. 50-150 cm in the alpine.

Weather Summary

Friday night

Mostly cloudy with no precipitation expected, light to moderate westerly ridgetop winds, and alpine temperatures in the -15 to -20 C range.

Saturday

Clearing throughout the day. Generally light winds from the west at ridgetop, with alpine temperatures warming slightly, in the -10 to -15 C range.

Sunday

Mostly sunny, light ridgetop winds and alpine temperatures around -10 C.

Monday

Mostly sunny, light ridgetop winds and alpine temperatures around -15 C.

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.