Avalanche Forecast

Issued: Mar 30th, 2021 4:00PM

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

Avalanche Canada ahanna, Avalanche Canada

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Rising temperatures coupled with spring sun can pack a punch and quickly initiate natural avalanche activity and weaken cornices. Be ready to back off slopes as the surface becomes moist. Moderate wind could help keep things cool, but could also be building new wind slabs.

Summary

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Tuesday night: Cloudy. Light to moderate northwest wind. Freezing level 500 m. Alpine temperature -7.

Wednesday: Sunny. Light to moderate southwest wind. Freezing level 2000 m. Alpine temperature -1.

Thursday: Scattered flurries. Moderate southwest wind. Freezing level 2000 m. Alpine temperature -3.

Friday: Scattered flurries. Light to moderate southwest wind. Freezing level 1800 m. Alpine temperature -5.

Avalanche Summary

A natural storm slab avalanche cycle was observed to have run during the storm size 3-3.5 in the Selkirks and in the Monashees to size 2.5. Several skier and explosive triggered size 1 wind slabs were reported Monday, and Tuesday. A skier triggered size 2.5 involvement in neighboring Glacier National Park resulted in lost gear and minor injuries.

Notable reports of avalanche activity prior to the storm include:

  • On Saturday, several natural cornice falls triggered size 2-3 avalanches. One of which is suspected to have run on a deeply buried crust near the base of the snowpack. 
  • On Thursday a natural size 3 was observed on a east aspect at 1800 m in the Valhallas. The crown was 100 cm thick, but no other details are known.

Snowpack Summary

20-50 cm of recent snow in the Selkirk mountains and 10-20 in the Monashees has seen some redistribution by southwest to northwest wind, and seems to be bonding well with underlying surfaces. Dry snow that sees direct sun or experiences above freezing temperatures for the first time Wednesday may become reactive as it settles rapidly. Crusty surfaces below treeline will become moist with rising freezing levels.

At alpine and treeline elevations, a few layers of note are buried 50-100 cm deep including a layer of small surface hoar crystals on shady, wind-sheltered aspects and a series of crusts on solar aspects and below 1800 m. Overall the snow seems to be bonding well to these interfaces, although there have been a few isolated avalanches running on crusts layer in the past week.

Terrain and Travel

  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • Remember that in the spring strong solar radiation and warm temperatures can weaken the snow in a matter of minutes.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Problems

Storm Slabs

An icon showing Storm Slabs

Storm slabs are most likely to be reactive:

- at elevations experiencing rapid warming for the first time (1700-2000m)

- on dry southerly aspects seeing strong sun for the first time

- in freshly wind loaded terrain features at upper elevations

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

An icon showing Cornices

Cornices are fragile due to rapid growth from recent snow and wind. Strong sun will further weaken them. Cornice falls are dangerous in their own right and they can also trigger slabs on slopes below.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

An icon showing Loose Wet

Wet loose avalanches are possible below treeline.

Dry loose avalanches will be very likely on steep south facing slopes at upper elevations when the sun comes out in the afternoon.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 1.5

Valid until: Mar 31st, 2021 4:00PM