Avalanche Forecast
Issued: Apr 18th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
LP,
Avalanche Canada
Monitor recent snowfall amounts carefully, as there is variation throughout the region. 5-45 cm of new snow fell with strong SW winds as a cold front passed through Monday. Moderate terrain choices with limited overhead hazard are recommended until the storm snow settles and bonds.
Summary
Confidence
Moderate
Avalanche Summary
On Monday, areas around Yoho and Lake Louise got 30-45 cm of new snow and saw natural avalanche activity out of steep terrain up to size 3 in the storm snow. On Tuesday, Lake Louise patrol reported explosive triggered avalanches to size 1.5, 25-30 cm deep, involving the storm snow.
Other areas of the forecast area got significantly less snow and only saw a few small wind slabs in steep lee-loaded terrain in the alpine.
Snowpack Summary
There is 5-30cm of settled snow from Monday's storm that was accompanied by strong SW winds. The greatest amounts were received in the Lake Louise area. The storm snow sits over buried sun crusts that are present to ridge crests and faceted layers on shady aspects. Multiple buried crusts are present in the top 50-70 cm on solar aspects. The basal depth hoar is present at the bottom of the snowpack and remains facetted and weak.
Lower elevations have a temperature crust on all aspects.
Weather Summary
5-10 cm expected Tuesday night, with the greater amounts between Banff and Highwood Pass.
Another 5-10 cm is expected on Wednesday. Amounts are variable given the convective nature of the snowfall, where some locations may receive greater than 10 cm.
Winds should remain light Tuesday night and Wednesday.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Storm Slabs
Areas with 15+ cm of fresh snow will have a storm slab problem. The new snow may fail naturally and will be reactive to human triggering especially over buried sun crusts. Lee areas with newly formed wind slabs and fresh cornices are also a concern.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The weak basal facets, as well as mid-pack facets and crusts, remain a significant concern. Many large avalanches on these layers during a recent avalanche cycle indicate that this problem will continue to be a concern until the end of the season.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 19th, 2023 4:00PM
