Avalanche Forecast

Issued: Apr 3rd, 2022 4:00PM

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

Avalanche Canada rbuhler, Avalanche Canada

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The ongoing storm is expected to develop touchy storm slabs for Monday. Large, natural avalanches should be expected and very conservative terrain selection is essential including avoiding exposure to overhead hazards.

Summary

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

A major storm system is expected to continue to impact the region until Monday night and may end up lingering into Tuesday morning. Forecast snowfall amounts are quite uncertain and may have substantial variability across the region. 

Sunday Night: Snowfall 20-40 cm, strong to extreme SW wind, freezing level low around 1000 m/high around 1300 m. 

Monday: Snowfall 15-30 cm, strong SW wind, freezing level high around 1100 m. 

Tuesday: A mix of sun and cloud with lingering flurries in the morning, moderate W wind easing through the day, freezing level high around 1300 m.

Wednesday: Mainly sunny, light variable wind, freezing level high around 1600 m.

Avalanche Summary

An early report from Sunday includes several small skier triggered storm slabs which were sliding on a melt-freeze crust. One of these was remotely triggered from 10 m away suggesting a weak bond between the storm snow and the underlying crust. 

On Saturday, explosive triggered a few cornices including a size 2 cornice which triggered a size 1 storm slab on the slope below. Ski cutting was triggering size 1 soft slabs with 5-15 cm of recent storm snow sliding on the firm melt-freeze crust. A skier also triggered a size 1 wind slab on a north aspect at 2100 m elevation which was 15 cm thick. This MIN report describes a small skier triggered wind slab which slid on a hard crust and a small natural avalanche which was solar triggered. 

On Friday, explosives triggered a couple size 1-2 cornices. One of these cornices triggered a slab avalanche on a northwest aspect in the alpine which likely failed on the mid-March interface down 50 cm.

Snowpack Summary

As of Sunday afternoon, weather stations were showing 20-30 cm of new storm snow accumulation. This storm snow has buried a strong, supportive crust which extends to mountain top on solar aspects and to around 2200 m on northerly aspects. Strong southwest wind will be redistributing the new storm snow in exposed high elevation terrain forming touchy wind slabs and developing large cornices. The new storm snow was reported to be moist below 1300 m on Sunday. 

Below the crust, the upper snowpack consists of a number of crust/facet/surface hoar interfaces buried in March that seem to have bonded well during the recent warm weather. 

The middle and lower snowpack are generally strong and well bonded. 

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Make conservative terrain choices and avoid overhead hazard.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

Problems

Storm Slabs

An icon showing Storm Slabs

Ongoing snowfall is expected to continue to build touchy storm slabs on Monday and a natural avalanche cycle is expected. The storm snow may be failing on a hard underlying melt-freeze crust or on interfaces within the storm snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Cornices

An icon showing Cornices

Large cornices will continue to grow during the storm and have the potential to fail naturally. 

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Loose Wet

An icon showing Loose Wet

Rain at lower elevations will destabilize the upper snowpack. Loose wet avalanches are most likely at elevations where rain soaks recent snowfall overlying a hard melt-freeze crust.

Aspects: All aspects.

Elevations: Below Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Apr 4th, 2022 4:00PM