Avalanche Forecast

Issued: Nov 28th, 2020 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Deep Persistent Slabs.

Avalanche Canada JSmith, Avalanche Canada

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 15-25 cm. of recent storm snow and strong southerly winds have created wind slabs at treeline and above. These wind slabs may be surprisingly reactive in areas where they are sitting on a layer of small surface hoar.  

Summary

Confidence

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

Weather Forecast

 SATURDAY NIGHT: Few clouds / Moderate, south wind / alpine low temperature -12 / Freezing level valley bottom.

 SUNDAY: Mix of sun and cloud / Moderate, south wind / alpine high temperature -5 / Freezing level 1000 m.

 MONDAY: Snow, 5-10 cm / Strong, south wind / alpine high temperature -5 / Freezing level 1000 m.

TUESDAY: Mostly sunny / Light, northwest wind / alpine high temperature -6 / Freezing level valley bottom.

Avalanche Summary

There have been very few reports of avalanches in the region, however, observations are very limited at this time. Several recent MIN reports from neighboring Glacier National Park have reported human triggered avalanches on small surface hoar below the recent storm snow.

If you get out into the mountains, please consider sharing your observations on the Mountain Information Network!

Snowpack Summary

 15-25 cm of recent storm snow and strong southerly winds have created wind slabs at treeline and above. These wind slabs may be surprisingly reactive in areas where they are sitting on a layer of small surface hoar. This layer has been described as “spotty” and may only be found in specific areas. A crust from early November exists down approximately 90-130 cm. This crust has been observed to have weak, sugary facets above and below it. Recent tests on this layer indicate that it may be bonding poorly, and has the potential to be triggered by humans. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid lee and cross-loaded terrain.

Problems

Wind Slabs

An icon showing Wind Slabs

 15-25 cm of recent storm snow and strong southerly winds have created wind slabs at treeline and above. These wind slabs may be surprisingly reactive in areas where they are sitting on a layer of small surface hoar 

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

A crust from early November exists down about 80-100 cm. This layer has weak, sugary facets above and below it. This layer is most likely to be reactive to human triggers in shallow, rocky, snowpack areas in the alpine.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Nov 29th, 2020 4:00PM