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Archived

Avalanche Forecast

Dec 20th, 2019–Dec 21st, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Banff Yoho Kootenay.

An excellent day to check out the local ski area.

Avoid overhead hazard and avalanche terrain.

Weather Forecast

The infamous atmospheric river did not disappoint today and the storm continues on through Saturday night with another 30-40cm forecasted. Temps will remain mild on Saturday with an alpine high of -4 and a freezing level up to 1500m. Winds will be moderate, gusting to strong from the S-SW. Clearing trend on Sunday with cooler temps and light winds.

Snowpack Summary

20-35cm of storm snow in the past 24hrs accompanied by moderate Southerly winds is forming a storm slab in the alpine and at tree line. Below the new snow the snowpack structure is generally weak, consisting of facets and depth hoar. The Nov crust is present up to 2500m and ~30 cm up from ground. Snowpack depths at treeline range from 90-160 cm.

Avalanche Summary

Poor visibility has obscured any avalanche observations, but a natural avalanche cycle is either happening or about to happen. Avoid avalanche terrain.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

Avalanche Problems

Storm Slabs

A touchy storm slab is forming and will become more sensitive to human triggering as the storm continues on Saturday.

  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Use caution in lee areas in the alpine and treeline. Storm snow is forming reactive slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 3

Loose Dry

As the snow accumulates, expect sluffing and point releases from steep, rocky terrain and gullies.

  • If triggered dry loose point releases can form deeper deposits in terrain traps.
  • Be careful of loose dry power sluffing in steep terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 2

Deep Persistent Slabs

The weak, faceted mid and lower pack is being stressed by the new storm snow and might be reaching threshold. Lots of uncertainty surrounds this layer, but if triggered it would result in a large avalanche.

  • Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 3.5