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Archived

Avalanche Forecast

Dec 19th, 2019–Dec 20th, 2019
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
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
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
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high

Regions: Glacier.

The Avalanche Hazard is rated Considerable for TODAY, but will increase to high TONIGHT and TOMORROW!

Weather Forecast

Cloudy with sunny periods and isolated flurries today, freezing levels will hover around 800m, and winds will be light to moderate from the South-South West. The Atmospheric River will bear down upon us later this afternoon, and last until Sunday morning. Depositing 9cm tonight, 30+ cm Friday, 30+cm Saturday at Tree-Line.

Snowpack Summary

60-70cm of new snow now buries the Dec 11 surface hoar layer. Previous new snow, and moderate winds built storm slabs at all elevations. The Nov 23rd surface hoar/crust/facet combo is down +/-120cm but has become increasingly stubborn in testing. Both of these interfaces are expected to wake up this weekend!

Avalanche Summary

On Tuesday and Tuesday evening we had a decent natural cycle to size 3, dusting up-tracks and the Highway. Limited new activity was observed yesterday. A natural cycle will start early tomorrow morning as the atmospheric river passes over Rogers Pass, rapidly loading start zones with new snow accompanied by strong wind and rising temperatures.

Confidence

Timing of incoming weather systems is uncertain

Avalanche Problems

Storm Slabs

Storm slabs are primed for human-triggering on steep unsupported terrain features. Storm slabs may step down to the Dec 11th surface hoar layer, which can be found 60-70cm below the surface.

  • Watch for fresh storm slabs on exposed lee slopes at all elevations.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2.5

Persistent Slabs

70cm+ of storm snow covers the widespread Dec 11th Surface Hoar(SH), size 5-12mm. This sliding layer is expected to wake up tomorrow naturally, but is still probable for human triggering today.

  • Avoid shallow snowpack areas where triggering is more likely.
  • Persistent slabs may be more sensitive to human triggering on solar asp where it sits on sun crust

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3