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Archived

Avalanche Forecast

Dec 8th, 2020–Dec 9th, 2020
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
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.

The storm came in heavy and warm, and now we are in a natural avalanche cycle.

Avoid any overhead hazard today as we expect avalanches to be running all the way into the valley bottoms.

Weather Forecast

One more storm day, then the weather eases into slightly cooler, sunnier conditions.

Today: Periods of snow, 10-15cm. FZL 1500m, wind SW-25-40km/h

Tonight: Isolated flurries, FZL dropping to 1200m, wind W 10-25km/h

Wed: Mix of sun/cloud, FZL 900m, light W winds

Thurs: mix of sun/cloud, FZL 500m, light W winds

Snowpack Summary

30+cm of warm snow and mod/strong SW winds have created a storm slab. It sits on a significant widespread surface hoar (SH) layer at tree-line and lower elevations. In the alpine, the storm slab rests on a crust on steep solar aspects. Several SH layers exist in the mid-upper pack, while the Nov 5 crust lurks as a deep persistent weakness.

Avalanche Summary

There is an ongoing natural avalanche cycle to sz 3 affecting all elevation bands.

Confidence

Avalanche Problems

Storm Slabs

The warm, heavy new snow has created a cohesive 25-40cm storm slab. It sits on widespread surface hoar (SH) or on a crust on steep solar aspects. Locations of large SH will be particularly touchy (below tree-line).

  • Be aware of the potential for wide propagations.
  • Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3

Deep Persistent Slabs

The heavy storm slab may stress the snowpack enough to trigger this deep persistent slab. If avalanches step down to this layer, expect to see very large avalanches running into the valley bottom.

  • Avoid shallow snowpack areas where triggering is more likely.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3.5