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Archived

Avalanche Forecast

Dec 6th, 2019–Dec 7th, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
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
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

Regions: Glacier.

We are in mid-storm conditions. Natural avalanches are likely. Avoid lingering in runout zones, as slides may reach the valley bottom today.

Weather Forecast

Moderate to heavy snow fall is expected in Rogers Pass today with up to 15cm of accumulation. Strong SW winds arrive this afternoon. Freezing levels rise to 1600m with an alpine high of -2.0. An arctic front will bring another 10cm of snow on saturday before a high pressure ridge builds later in the weekend.

Snowpack Summary

20 cm of low density snow fell overnight and sits atop 70cm of settling storm snow. Winds from the previous storm created slabs on lee alpine features which are now concealed by the new snow. The November 23rd surface hoar/crust layer is buried +100cm and remains reactive in stability tests. Tree wells are getting deeper and deserve extra caution.

Avalanche Summary

Natural avalanche activity tapered off yesterday, with only 2 solar triggered size 2.0 avalanches observed from steep rocky terrain. We are in another storm cycle and expect natural avalanche activity to pick today, especially once the forecasted SW winds arrive.

Confidence

Avalanche Problems

Storm Slabs

20cm of new snow is expected to form into a reactive storm slab as the day progresses. The new snow sits atop a previous storm slab from December 3rd that is still poorly bonded. The new snow may trigger this buried layer.

  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Use caution in lee areas in the alpine and treeline. Storm snow is forming reactive slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1.5 - 3

Persistent Slabs

Storm slabs have the potential to step down to a buried weak layer (Nov 23 Surface Hoar/ Crust) now down +100cm. It consists of surface hoar at treeline and below, and a crust on steep solar aspects into the alpine.

  • Minimize overhead exposure; avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2.5 - 3.5