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Avalanche Forecast

Apr 11th, 2023–Apr 12th, 2023
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
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Little Yoho.

A major avalanche cycle occurred in the forecast region Tuesday afternoon with slides up to size 3.5. Conditions will be ripe for human triggering on Wednesday.

Confidence

Moderate

Avalanche Summary

A cycle up to size 3.5 peaked Tuesday afternoon. Most major avalanche paths ran full path in the Banff area. Included are Cascade Waterfall, Urshole Gully, Professors, and Bourgeau Left. Lake Louise patrol also reported a widespread cycle in the immediate backcountry with deep slabs observed in Purple Bowl and Redoubt Bowl size 2.5.

Snowpack Summary

Up to 40cm of storm snow in the alpine (end of day Tuesday) overlies previous windslabs and suncrusts with rain saturated snow below 1800m. Storm slabs can still be expected in the alpine and tree-line areas.

Several buried crusts can be found in the top 50-60 cm on solar aspects. The November depth hoar at the base of the snowpack remains a concern only in shallow areas of the Yoho sub-region.

Weather Summary

Diminishing wind into the light range is expected on Wednesday. There is a possibility of localized convective flurries, with amounts potentially up to 10cm. Valley temps should be slightly above zero, with alpine temps holding steady around -10.

Avalanche Problems

Storm Slabs

Up to 40cm of storm snow has fallen and has created widespread storm slabs in alpine and tree-line areas. The storm snow will need several days to settle and bond. In the alpine wind will have contributed to making the storm slabs even thicker.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1.5 - 2.5

Deep Persistent Slabs

The November basal facets at the base of the snowpack have been mainly dormant in this region. This new load (of snow above 2000m and rain below) will be a good test on this layer. There is some uncertainty as to whether this layer will "wake up" in the Yoho region.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3.5