North Columbia Avalanche Forecast

Issued: Jan 6th, 2021 4:00PM

Thu Jan 7th Current Conditions
Alpine Considerable Treeline Considerable Below Treeline Considerable
Fri Jan 8th 2 Day Outlook
Alpine Considerable Treeline Considerable Below Treeline Considerable
Sat Jan 9th 3 Day Outlook
Alpine Considerable Treeline Considerable Below Treeline Considerable

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

The stormy weather may be over, but the snowpack is complex. Resist the urge to venture into bigger terrain until the snowpack has had a chance to gain some strength. The best riding is likely to be found on low angle slopes in wind sheltered areas.

Summary

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

WEDNESDAY NIGHT - Mainly cloudy with a few flurries / light southwest wind / alpine low temperature near -9 

THURSDAY - A mix of sun and cloud/ light southwest wind / alpine high temperature near -4 

FRIDAY - A mix of sun and cloud / light to moderate southeast wind / alpine high temperature near -2 

SATURDAY - Mainly cloudy / light south wind / alpine high temperature near -6

Avalanche Summary

Storm slabs will likely be easiest to trigger in wind loaded areas, as well as in the trees where they may rest on a buried surface hoar layer.

At the time of publishing, numerous natural storm slab avalanches size 2-3.5 had been reported in the neighboring Glacier National Park region on Wednesday.

A few natural and human triggered storm slab avalanches size 1-2 were reported on Tuesday. Natural storm slab avalaches up to size 3 were also reported in the nearby Glacier National Park region on Tuesay.

It is notable that there were several human triggered avalanches reported at lower elevations in the neighboring Glacier National Park region on Monday. These avalanches highlight the potential to trigger avalanches in the trees. Reports of these can be viewed here, here, and here.

On Sunday, numerous explosive triggered storm slab avalanches up to size 3.5 were reported just west of Revelstoke.

On Saturday, a skier triggered a size 2 slab avalanche near the Gorge area. See the excellent MIN report here.

Snowpack Summary

The recent stormy weather has brought around 30-75 cm of new snow to the region with some moderate to strong winds. Storm slabs are likely widespread. In many areas, the storm snow sits on a weak layer of surface hoar that was buried around Christmas. This layer continues to be of concern, mainly at treeline and below treeline.

Two persistent weak layers buried in early/mid-December are now down about 90-150 cm. The form and distribution of these layers are highly variable and conditions may differ significantly from one valley to the next. The first layer 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. This layer also remains a concern.

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • 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 a persistent slab.
  • Uncertainty is best managed through conservative terrain choices at this time.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Possible-Likely

Expected Size

1.5 - 2.5

Recent new snow with some moderate wind has created widespread storm slabs that are still likely to be triggered by humans in many areas.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Unlikely-Possible

Expected Size

2 - 3.5

Two persistent weak layers buried in early/mid-December are now 90-150 cm below the surface. The form and distribution of these layers are highly variable and may vary significantly from one valley to the next, and between elevations bands.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 7th, 2021 4:00PM