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Avalanche Forecast

Archived

Dec 3rd, 2022–Dec 4th, 2022

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

Lizard-Flathead, Akamina, Flathead, Lizard.

Stick to conservative terrain and give storm snow time to settle and bond before pushing into bigger avalanche terrain, keep an eye out for active wind transport building fresh wind slabs.

Small avalanches have the potential to trigger deeper weak layers. Assess conditions as you travel and gain information.

Confidence

Moderate

Avalanche Summary

Reports from Thursday indicated reactive conditions with small, naturally triggered storm slabs occurring in steep terrain features. Explosive control work since Wednesday has produced slab avalanches up to size 2. We expect conditions to remain primed for human triggering, particularly in wind loaded terrain features.

Numerous reports of small loose dry avalanches (sluffing) within the recently fallen low-density surface snow.

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

Snowpack Summary

Up to 100 cm of recent storm snow has fallen within the last week. In wind affected terrain this will be redistributed into deeper deposits by recent variable winds. In sheltered terrain, cold temperatures will likely maintain low density snow with little cohesion.

The middle of the snowpack consists of weak sugary layers of facets and surface hoar. A widespread rain crust remains near the ground at treeline and below treeline.

At treeline, snowpack depths vary from 120-200 cm.

Weather Summary

Saturday Night

Mostly clear skies with dropping temperatures. Moderate westerly winds. No snowfall expected.

Sunday

Clear skies to start with increasing cloud. Light and variable winds. Alpine highs around -9. Isolated flurries may bring trace amounts late in the day.

Monday

Cloudy with up to 2 cm of snow. Winds are generally moderate from the west with strong gusts around ridgelines. Alpine highs of -12.

Tuesday

5 cm of snow possible with cloudy skies. Alpine highs of -12. Winds are generally moderate from the west with strong gusts around ridgelines.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.