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Avalanche Forecast

Nov 30th, 2020–Dec 1st, 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
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Purcells.

  

Lingering wind slabs may remain surprisingly reactive to human triggers in areas where they are sitting on top of a layer of small surface hoar.

Confidence

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

Weather Forecast

  

MONDAY NIGHT: Clearing skies / Moderate, northwest ridgetop wind / alpine low temperature -14 / Freezing level valley bottom.

TUESDAY: Sunny / Light, northwest ridgetop wind / alpine high temperature -3 / Above freezing layer of air moving in late afternoon and creating a strong temperature inversion with warm air above roughly 2000 m.

WEDNESDAY: Sunny / Light, southwest ridgetop wind / alpine high temperature +1 / Strong inversion with an above freezing layer of air above 2000 m.

THURSDAY: Sunny / Light, southwest ridgetop wind / alpine high temperature +1 / Strong inversion with an above freezing layer of air above 2000 m.

Avalanche Summary

Check out this notable MIN report of numerous human triggered avalanches from Quartz Creek on Saturday. The buried layer of small surface hoar that caused this avalanche could catch riders by surprise.

Data is very sparse in this region. Please submit your observations to the Mountain Information Network.

Snowpack Summary

  

Around 5 cm of new snow on Monday has covered a layer of surface hoar found primarily at treeline and below. The strong southwest winds from last week created wind slabs on lee features at treeline and above. There were a couple human triggered avalanches on a small layer of buried surface hoar. This layer has been reported as "spotty" and is most likely to be present in sheltered areas. There is a crust from early November that is down approximately 50-75 cm. This layer has been observed to have weak, sugary facets above and below it and is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky, snowpack areas in the alpine..

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • In times of uncertainty conservative terrain choices are our best defense.
  • Closely monitor how the new snow is bonding to the old surface.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Avalanche Problems

Wind Slabs

Lingering wind slabs may remain surprisingly reactive to human triggers in areas where they are sitting on top of a layer of small surface hoar.

Aspects: North, North East, East, South East, South, North West.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Deep Persistent Slabs

A crust from early November exists down about 50-75 cm. This layer has weak, sugary facets above and below it. This layer is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky, snowpack areas in the alpine.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1.5 - 2.5