Avalanche Forecast

Issued: Apr 2nd, 2021 4:00PM

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

Avalanche Canada JSmith, Avalanche Canada

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 Additional snow and wind Friday night will continue to form fresh storm slabs. Use small slopes with low consequence to test the bond of the new snow. Be especially cautious in wind affected terrain. 

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

  

FRIDAY NIGHT: Snow; 10-20 cm. / Strong, southwest ridgetop wind / alpine low temperature -4 / Freezing level 500 m.

SATURDAY: Snow; 5-10 cm. / Moderate, southwest ridgetop wind / alpine high temperature 1 / Freezing level 900 m.

SUNDAY: Mostly cloudy / Moderate, northwest ridgetop wind / alpine high temperature 0 / Freezing level 800 m.

MONDAY: Cloudy / Strong, west ridgetop wind / alpine high temperature 0 / Freezing level 900 m.

Avalanche Summary

On Thursday, explosive triggered storm slab avalanches up to size 3 were reported in the alpine.

On Wednesday, naturally triggered glide slab avalanches were reported up to size 3. Glide cracks releasing as full depth glide slab avalanches are extremely difficult to predict. Best practice is to avoid slopes with glide cracks.

Snowpack Summary

15-20 cm of recent snow and wind have formed reactive storm slabs at treeline and above. Snow will continue to accumulate overnight on Friday, forming fresh storm slabs. Cornices are large and capable of triggering large avalanches when they fail.

At lower elevations, the snow was mixed with rain, soaking the snow surface, which then formed a hard crust. 

At higher elevations, the new snow has added significant load to a couple of deeply buried weak layers. The first persistent weak layer was buried in mid-March and is around 100-180 cm. deep. It consists of surface hoar on sheltered northerly aspects around treeline and down between 150 to 250 cm. is another layer of surface hoar and facets, buried in mid-February. At this time, these layers linger in the snowpack but haven't recently been a reactive avalanche problem. 

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

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Start with conservative lines and watch for clues of instability.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Storm Slabs

An icon showing Storm Slabs

Reactive storm slabs are expected at upper elevations, especially in wind-loaded areas.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 2.5

Cornices

An icon showing Cornices

Cornices are large and looming along many ridgelines, and have likely grown with the recent snow and wind. They are capable of triggering very large avalanches when they fail.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Apr 3rd, 2021 4:00PM