Avalanche Forecast
Issued: Mar 12th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Cornices, Persistent Slabs and Loose Wet.
JSmith,
Avalanche Canada
Things are looking HOT up high for the next couple days. Overhead hazards such as cornice failures triggering large persistent slab avalanches will be a primary concern. Recently unreactive weak layers in the snowpack may become active with the rapidly rising freezing levels.
Summary
Confidence
Moderate - Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather.
Weather Forecast
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FRIDAY NIGHT: Clear / Light, northeast ridgetop wind / alpine low temperature -11 / Freezing level valley bottom.
SATURDAY: Sunny / Light, southeast ridgetop wind / alpine high temperature 3 / Freezing level rapidly rising to 2500 m.
SUNDAY: Sunny / Light, southwest ridgetop wind / alpine high temperature 3 / Freezing level 2400 m.
MONDAY: Mix of sun and cloud / Light, northeast ridgetop wind / alpine high temperature 1 / Freezing level 2200 m.
Avalanche Summary
No avalanches were reported in this region on Thursday. However, the rapidly rising freezing level and sunny skies on Saturday are expected to elevate the avalanche hazard through the weekend.
On Tuesday, a size 2.5 cornice failure was reported.
There was a MIN report on Monday of a small wet loose point release triggering a size 2 slab avalanche around 30 cm. deep on a south aspect. See MIN HERE.
Snowpack Summary
Dry soft snow can be found on shaded aspects above around 1500 m. On south-facing slopes and at lower elevations expect crusty snow in the morning and soft, moist snow in the afternoon. Lingering wind slabs and large cornices still pose a hazard close to alpine ridgelines.
A Persistent weak layer of facets 40-60 cm. deep that was buried in mid-February was reactive in the north of the region earlier this month but no avalanches have been reported on this layer since Mar. 3rd. There are several other weak layers deeper in the snowpack composed of old surface hoar, facets and/or crusts, all of which have been recently unreactive.
Big warm ups, like the one headed our way this weekend often awaken dormant weak layers resulting in large avalanches. Steep, rocky, convex terrain with a shallow or thin to thick snowpack are examples of places where triggering these layers are more likely.
Sunshine and warm temperatures often cause large cornice failures which are hazardous on their own and can also trigger large avalanches on deeper weak layers that the weight of a single rider would not trigger.
Terrain and Travel
- Avoid exposure to slopes that have cornices overhead.
- Cornice failure may trigger large avalanches.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Problems
Cornices
Rapidly rising freezing levels and sunny skies significantly increase the likelihood of cornice failures which are hazardous on their own and can also trigger large avalanches on deeper weak layers that the weight of a single rider would not trigger. Avoid exposure to slopes that have cornices overhead.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
Big warm ups, like the one headed our way this weekend often awaken dormant weak layers resulting in large avalanches. Steep, rocky, convex terrain with a shallow or thin to thick snowpack are examples of places where triggering these layers are more likely.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Naturally triggered wet loose avalanches are likely, especially on steep solar aspects in the alpine.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 13th, 2021 4:00PM
