Avalanche Forecast

Issued: Mar 6th, 2021 4:00PM

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

Avalanche Canada astclair, Avalanche Canada

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New snow and wind will elevate the avalanche danger. Triggering avalanches at upper elevations is likely, especially in wind-drifted areas. Continue to make conservative terrain choices and steer clear of cornices while the snow settles and stabilizes. 

Summary

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

A parade of storms continues through the weekend

Saturday night: Overcast, 5-10 cm of snow, light south wind increasing to moderate, freezing level dropping to 700 m. 

Sunday: Mostly cloudy, 10-20 cm of snow, moderate southwest wind, freezing level near 1000 m. 

Monday: Partly cloudy, isolated flurries with trace accumulations, light east wind, freezing level near 1200 m.

Tuesday: Mainly sunny, light variable wind, freezing level near 1400 m.

Avalanche Summary

Explosive mitigation on Saturday produced numerous large cornice and storm slab avalanches, with 50-100 cm crown depths. Explosives also released a very large (size 3) wind slab avalanche on a northeast aspect above 2000 m. 

Reports indicate that a natural avalanche cycle occurred during the storm on Friday, with small to large (size 1-2.5) avalanches releasing in the storm snow across aspects and elevations. Check out this MIN report from Hanging Lake.

Snowpack Summary

Another 15-25 cm of snow is forecast to accumulate by midday on Sunday above 1000 m. This will add to the 50-80 cm of snow that blanketed slopes above 1600 m on Friday. The recent snow has been accompanied by strong south winds, forming touchier slabs on leeward slopes. Pay attention to how wind has redistributed snow and investigate the bond of the new and old snow interfaces as you travel in the backcountry on Sunday. Massive cornices exist on ridgelines, which can act as triggers on slopes below. A cooling trend over the weekend is expected to settle and strengthen lower elevation slopes that became saturated with rain. 

In isolated areas with a shallower snowpack in the region, a layer of facets, spotty surface hoar, and/or crusts buried in mid-February may still be preserved. There have been no avalanches reported on this layer; however, large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow and wind have the potential to this deeper layer in areas where it may still exist.

The mid and lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Cornice failure may trigger large avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs

Strong south winds have had ample snow to drift into reactive wind slabs on lee features at upper elevations. Watch for cracking, changes in snow stiffness, and the pattern of wind-drifting in the terrain where you are traveling. These wind slabs are likely and have the potential to be very large. 

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1.5 - 3

Cornices

An icon showing Cornices

Cornices are large and looming, and they may release naturally under the current conditions. Cornice falls can act as triggers on slopes below.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 2.5

Storm Slabs

An icon showing Storm Slabs

Recent snowfall has blanketed the terrain with a widespread storm slab problem. Monitor for the reactivity of the new snow and old snow interfaces and for density changes within the new snow where you travel.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

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