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Archived

Avalanche Forecast

Dec 20th, 2019–Dec 21st, 2019
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
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

Regions: Glacier.

High Avalanche Danger today through Saturday! A great day to avoid avalanche terrain.

Weather Forecast

An atmospheric river of moisture from the Pacific has begun to dump on the Selkirks. The forecast calls for 30cm in the next 24 hours with an additional 20cm through the day Saturday. Moderate to strong SW winds will accompany this storm front accompanied by freezing levels rising to 1500m. The storm should abate late Saturday.

Snowpack Summary

Field tests and observations found a reactive storm slab down 20cm. 80cm+ of snow now buries the Dec 11 surface hoar layer. Previous new snow, and mod winds built storm slabs at all elevations. The Nov 23rd surface hoar/crust/facet combo is down +/-130cm has become increasingly stubborn in testing. These interfaces are expected to wake up today.

Avalanche Summary

A fresh avalanche cycle began last night at 10pm and is ongoing. We expect a widespread avalanche cycle to continue at all elevations through to Saturday afternoon when the winter storm is forecast to abate.

Confidence

Forecast snowfall amounts are uncertain

Avalanche Problems

Storm Slabs

A touchy storm slab formed Dec 19 over a Stellar layer down 30cm. This layer is expected to be widespread and sensitive to human triggering.

  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 2.5

Persistent Slabs

The Dec 11th Surface Hoar(SH), size 5-12mm is down 80cm+. This sliding layer is expected to wake up tomorrow naturally when storm slab releases overload it. This will result in large avalanches likely running to valley bottom.

  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3

Deep Persistent Slabs

The Nov 15 melt freeze crust is down deep in the snowpack. This layer may reach threshold for overload from avalanches triggered in upper snowpack layers. The resulting avalanches will be large.

  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 3.5