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Avalanche Forecast

Archived

Dec 9th, 2022–Dec 10th, 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, human triggered possible.
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.

New snow will need some time to stabilize.

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 new snow that fell Thursday night quickly formed a storm slab. This slab produced several avalanches up to size two that were triggered with explosives and ski cutting. Natural activity was also seen from this storm slab.

Snowpack Summary

Thursday night brought us 15 cm of fresh snow. With warmer temperatures and more water in this snow, it will feel heavier than the snow we have been getting over the last week. That snow came with southwesterly winds and was redistributed, building wind slabs. Where the wind did not have an effect, the new heavier snow will be sitting on about 30 cm of lighter snow.

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 to 200 cm.

Weather Summary

Friday Night

Mainly cloudy, 5 cm accumulation, winds southwest 15 km/h, temperature -9 C at 1500 m.

Saturday

Cloudy, 8 cm accumulation, winds southwest 15 gusting to 25 km/h, temperature -5 C at 1500 m.

Sunday

Mainly cloudy, 10 cm accumulation from the night previous, possible rain during the day, winds south 20 to 30 km/h, temperature 0 C at 1500m.

Monday

Cloudy with sunny periods, trace accumulation, winds northeast 15 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.

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.