Avalanche Forecast

Issued: Feb 1st, 2021 4:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada kdevine, Avalanche Canada

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The South Coast has been bit by some intense snow and rain, which is keeping danger elevated. Avoid avalanche terrain.

Summary

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain. Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

MONDAY NIGHT - Snow and rain, 20-30 cm/mm / strong southwest wind / alpine low temperature near -1 / freezing level 1200m, falling to 800 m overnight

TUESDAY - Flurries, 5-10 cm / moderate southwest wind / alpine high temperature near -2 / freezing level 700 m

WEDNESDAY - Mainly sunny / light northwest wind / alpine high temperature near -4 / freezing level 

THURSDAY - Snow, 10-15 cm / strong west wind / alpine high temperature near -4 / freezing level 500 m, rising to 1000 m in the afternoon

Avalanche Summary

Natural avalanches are expected on Tuesday, and due to the presence of a persistent weak layer, they could be very large.

It has been a busy week for avalanche activity in the South Coast mountains, with natural and/or human triggered avalanches reported every day since last Monday. These avalanches have failed on the persistent weak layer that was recently buried. 

North Shore Rescue responded to a serious, but non-fatal avalanche incident last Tuesday evening on Cypress Mountain. One person was involved and was partially buried. The avalanche was a size 2 storm slab on a west aspect at approximately 1100 m and failed on the recently buried weak layer.

Snowpack Summary

20-30 cm/mm of precipitation is expected for Monday night, with falling freezing levels bringing some snow back to lower elevations. Around 5-10 cm is expected on Tuesday.

There is now about 125-175 cm of snow sitting on a widespread persistent weak layer. This weak layer consists of a crust that also has weak facets and surface hoar on top of it in many areas. This layer will probably take more time to gain strength than what is considered typical for the South Coast region.

Click here to watch North Shore Rescue's January 29 snowpack discussion, which illustrates this concerning snowpack structure.

Terrain and Travel

  • Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.

Problems

Storm Slabs

An icon showing Storm Slabs

Fresh and reactive storm slabs are expected to be widespread and easy to trigger.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Persistent Slabs

An icon showing Persistent Slabs

A widespread weak layer consisting of a crust, with facets and/or surface hoar on top of it is now down about 125-175 cm. This layer is expected to produce large avalanches for longer than what is typical after a storm on the South Coast.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Feb 2nd, 2021 4:00PM