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Archived

Avalanche Forecast

Dec 30th, 2020–Dec 31st, 2020
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
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
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: South Columbia.

  

Recently formed storm slabs will be most reactive in wind affected areas at treeline and above. Be especially cautious as you transition into wind affected terrain.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

WEDNESDAY NIGHT: Cloudy with isolated flurries; 0-3 cm. / Light, southwest ridgetop wind / alpine low temperature -12 / Freezing level valley bottom.

THURSDAY: Cloudy. / Light, northwest ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.

FRIDAY: Cloudy with flurries; 3-5 cm. / Strong, southwest ridgetop wind / alpine high temperature -5 / Freezing level rising to 900 m.

SATURDAY: Snow; 10-15 cm. / Strong, southwest ridgetop wind / alpine high temperature -4 / Freezing level 1300 m.

Avalanche Summary

On Monday, a couple skier triggered storm slab avalanches up to size 1.5 were reported on north and south aspects at treeline in the Monashees south of Revelstoke.

There have been numerous recent reports of dry loose avalanches(sluffs) running surprisingly fast and far below treeline.

Snowpack Summary

  

30-50 cm. of new snow since Christmas day fell on a mixture of faceted old snow and small surface hoar. The recent snow has been slow to settle into a slab and made for some great riding in many areas. This recent snow is most likely to be reactive in wind affected areas where the snow has been stiffened into a slab.

 Two persistent weak layers buried in early/mid Dec. are now 80 to 150 cm below the surface. The form and distribution of these layers are HIGHLY VARIABLE and have created conditions that can vary significantly from one valley to the next. The first layer down around a metre has been primarily reported as small surface hoar. The next layer has been reported as a thin freezing rain crust, surface hoar, or thick rain crust depending on elevation and location. As a result, diligent investigation of the snowpack is required to get a handle on localized conditions.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Avalanche Problems

Storm Slabs

  

The 35-50 cm. of recent snow is most likely to be reactive in wind affected areas where the snow has been stiffened into a slab.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 2.5

Persistent Slabs

Smaller storm slabs in motion may step-down to deeper layers resulting in very large avalanches. This problem can be avoided through conservative terrain choices.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3.5