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Archived

Avalanche Forecast

Dec 22nd, 2020–Dec 23rd, 2020
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

As the sky clears from a stormy week, a cautious approach to the backcountry is needed. Reactive storm slabs sit atop weak surface hoar and crusts. How well the new snow bonds to these layers will determine danger levels over the next few days.

Weather Forecast

A building high pressure ridge will dry the region out over the next few days.

Today: Cloudy with sunny periods, nil snow, ALP high -11*C, light/mod NW winds

Wed: Mix of sun/cloud, ALP high -4*C, light W winds

Thurs: Sunny with cloudy periods, ALP high -3*C with temp inversion in valley bottom, light SW winds

Snowpack Summary

140cm of snow over the last 6 days, along with strong S-SW winds and warm temps, has created a sensitive slab at all elevations. The Dec 13 surface hoar/facets are down 140cm+ and the Dec 7 crust/surface hoar layer is down 150cm+. The Nov 5 crust lingers near the base of the snowpack and several avalanches over the storm period stepped down to it.

Avalanche Summary

Artillery slab avalanche results to sz 4, including the Fidelity path reaching the valley floor last night. Suspect wide slab propagation on many alpine and tree-line start zones, likely on our persistent weak layers. Natural activity has decreased with the passage of the storm front, but N'ly winds are keeping S aspects active (ie. Mt Tupper).

Confidence

Due to the number of field observations

Avalanche Problems

Storm Slabs

Approx 140cm of storm snow from the last 6 days, accompanied by strong S/SW winds and mild temps, has created widespread storm slabs at the surface. N'ly winds overnight and today will create slabs on S'ly aspects, so watch for reverse loading.

  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Keep an eye out for reverse loading created by N-NE winds.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1.5 - 3

Persistent Slabs

~150cm sits on persistent layers of rain crust/ surface hoar/ or suncrust. Storm slabs have the potential to step down to these interfaces, triggering very large avalanches.

  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 4