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Avalanche Forecast

Archived

Dec 10th, 2021–Dec 11th, 2021

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Inland.

The best riding will be found in sheltered terrain. Keep your head up in wind loaded features near ridgeline.

 Avoid shallow rocky start zones, deeper weak layers are still a concern.

Confidence

High -

Weather Forecast

The fast moving pacific system will pass over on Friday night, leaving an unsettled weekend with light to moderate snowfall.

Friday Overnight: As the front tracks south, wind and snow will ease into the evening. Another 5-10 cm of accumulation can be expected with strong to extreme southwest wind easing to moderate at ridgetop by morning. Freezing levels lowering to valley bottom with alpine temperatures around -8 C.

Saturday: A mainly cloudy day with flurries. Moderate to strong ridgetop winds from the southwest, up to 5 cm of new snow throughout the day. Freezing levels at valley bottom with alpine temperatures around -15 C. 

Sunday: Partially cloudy with isolated flurries. Light to moderate southwest winds at ridgetop with alpine temperatures around -15 C.

Monday: A pleasant day. A mix of sun and cloud with light to moderate ridgetop winds from the southeast. Light flurries with trace accumulation. Ridgetop winds around -12 C. 

Avalanche Summary

On Thursday, our field team was out in the Telkwa mountains, they saw a few natural cornice failures up to size 2. 

If you do head out in the backcountry, please share your observations to the Mountain Information Network!

Snowpack Summary

This week's new snow accompanied by strong southwest winds have created wind slabs in the alpine and exposed areas at treeline. These new wind slabs will overlie older wind slabs from earlier in the week, amongst a variety of hard, wind effected surfaces. 

Below 1400m, a thin rain crust exists below this week's new snow. There have been reports of faceting around this crust with previous cold temperatures. A spotty surface hoar layer has been reported down ~100cm in the alpine and treeline. 

An early season crust can be found near the base of the snowpack. It has shown reactivity in the past week with large loads (explosives and cornice), creating large avalanches. We don't know how widespread this problem may be, but we are definitely keeping an eye on it, and would be avoiding large features and areas with thin to thick snowpack transitions.

Snowpack depth at treeline ranges from 150-200 cm, with higher values in the western part of the region, tapering to the east.

Terrain and Travel

  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.