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Archived

Avalanche Forecast

Dec 3rd, 2019–Dec 4th, 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
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

A natural avalanche cycle will peak this afternoon as strong winds trigger storm slabs!

Weather Forecast

Today: 15-20cm of new snow, winds will be light to moderate possibly gusting strong this afternoon out of the South, and the freezing level should stay below valley bottom (VB). Tonight: Another 10cm, winds increasing from the SW, and temps staying cool with the FL staying well below VB. Flurries for Wednesday, and a clearing trend on Thursday

                                                                                                                                                                                                                                     

Snowpack Summary

30 of new snow covers a facetted upper snowpack and previously wind affected surfaces. The two main interfaces to watch for are the storm slab interface down 30cm+ and the Nov 23rd surface hoar/ crust buried 40-60cm. Multiple buried crusts exist lower in the snowpack, but recent profiles are showing no significant shears on stability tests.

Avalanche Summary

We should see a natural avalanche cycle today with the 20cm of new snow that fell last night, plus another 15cm forecasted today! No new avalanches were reported from the highway or the backcountry yesterday; however, we are already starting to see some activity in the Highway corridor this morning!

Confidence

Avalanche Problems

Storm Slabs

30cm + of new snow in the last 24 hours, and another 15cm of forecasted snow will form storm slabs in the Alpine and at Treeline. Winds are forecasted to increase this afternoon, which should spike today's avalanche cycle!

  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 1 - 3

Loose Dry

The new snow will struggle to bond to the old surface layers and sluff easily in steep terrain. Loose dry avalanches can gain mass and potentially trigger storm slabs and or persistent slabs.

  • Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Persistent Slabs

Storm slabs have the potential to step down to a buried weak layer (Nov 23 Surface Hoar) now down 45-65cm. It consists of surface hoar at treeline and below, and a crust on steep solar aspects into the alpine.

  • Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: Treeline.

Likelihood: Possible

Expected Size: 1.5 - 2.5