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Avalanche Forecast

Archived

Dec 10th, 2022–Dec 11th, 2022

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

Regions

Lizard-Flathead, Akamina, Flathead, Lizard.

Snow continues to slowly accumulate adding to the storm slab.

An increase in temperature and wind will be added more load to our buried weak layer.

Assess conditions while you travel. Watch and feel for signs of instability such as whumpfing, cracking, and recent avalanches.

Confidence

Moderate

Avalanche Summary

The storm slab that formed from Thursday night's storm was reactive to explosives and ski cutand produced several decent size two avalanches. Some natural avalanches were also produced from this storm slab. People reporting in the MIN described hollow sounds and shooting cracks from wind slabs as well.

Snowpack Summary

Around 20 cm of fresh snow has fallen since Thursday. This sits on a variety of surfaces. In some places, it sits on wind slabs that were created by southwesterly winds that we experienced earlier this past week.

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

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

Weather Summary

Saturday Night

Cloudy, 10 cm accumulation, winds southwest 10 gusting to 30 km/h, temperature -7 C at 1500 m.

Sunday

Cloudy, 3 cm accumulation with possible snow showers, winds southeast 10 gusting to 25 km/h, temperature -3 C at 1500 m.

Monday

A mix of sun and cloud, 2 cm accumulation, winds northeast 20 to 30 km/h, temperature -5 C at 1500 m.

Tuesday

Mostly sunny, no accumulation, winds northeast 10 km/h, temperature -13 C at 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.