Avalanche Forecast

Issued: Jan 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 storm continues and avalanche activity is expected to remain widespread. Avoid avalanche terrain.

A complex snowpack led to several avalanche incidents in the last week, including a fatal avalanche near Pemberton on Monday.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

FRIDAY NIGHT - Snow, 20-30 cm / southwest wind 60-80 km/h wind / alpine low temperature near -3 / freezing level 1300 m

SATURDAY - Snow, 20-30 cm, with another 20-40 cm overnight / southwest wind 60-80 km/h, gusting to 100 km/h / alpine high temperature near -1 / freezing level 1200 m

SUNDAY - Flurries, 5-10 cm / southwest wind 30-50 km/hr / alpine high temperature near -4 / freezing level 1000 m

MONDAY - Flurries, 5-10 cm / southwest wind 20-40 km/h / alpine high temperature near -3 / freezing level 1000 m

Avalanche Summary

Avalanches are expected to be widespread on Saturday.

At the time of publishing, reports indicated that there was a lot of avalanche activity on Friday. This MIN report really highlights these conditions.

There were numerous reports of natural, human and explosives triggered size 1-2.5 avalanches on Thursday. Most of these were storm slabs, but at least two of them were persistent slab avalanches.

There was a fatal avalanche in the South Coast Inland region (near the Sea to Sky boundary) north of Pemberton in the Railroad Pass area on Monday that resulted in two fatalities. It was reported to be a size 2 persistent slab avalanche on a west aspect, around 1650 m. The RCMP press release can be viewed here, and the Avalanche Canada report can be found here.  

A size 2.5 avalanche was triggered on Monday by a skier on Rainbow Mountain, which resulted in a full burial and, thankfully, a successful rescue. The avalanche failed on a 60 cm deep crust and facet layer on a northeast aspect around 1800 m. 

A natural size 3 persistent slab avalanche was reported on Mount MacBeth on Monday, check out this MIN report for details of this observation.

These avalanches highlight the ongoing potential to trigger persistent weak layers in the snowpack. 

Snowpack Summary

There may be as much as 40-60 cm of new snow between Friday night and Saturday afternoon, forming widespread storm slabs.

This new snow will bring recent storm snow totals to over 120 cm.

The snowpack is currently complex, and two concerning weak layers may be present in the snowpack: 

  • The shallower layer, around 60 to 120 cm deep, includes feathery surface hoar crystals. This layer may be found in sheltered terrain features at treeline and lower alpine elevations, but has been reported as spotty across the region. 
  • The more widespread weak layer includes sugary faceted grains that sit on top of a hard melt-freeze crust. This layer ranges in depth from 50 cm to 150 cm due to the wind scouring and loading the snow in different terrain features over the past two weeks. The layer has been reported as being widespread up to around 2000 to 2200 m. 

There have been several recent human triggered avalanches on these layers. 

The remainder of the snowpack is well-settled.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Avoid areas with overhead hazard.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

Problems

Storm Slabs

An icon showing Storm Slabs

Storm slabs will be widespread and very reactive due to significant snow amounts and strong winds.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

A couple of problematic layers may be found around 50 to 150 cm deep, including weak layers of surface hoar and faceted grains above a hard melt-freeze crust. With the addition of a significant load of new snow, large avalanches may run naturally on these layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

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