Avalanche Forecast
Issued: Mar 17th, 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.
jsmith,
Avalanche Canada
Storm slabs formed earlier in the week may continue to be reactive to human triggers at upper elevations; especially on sunny aspects.
Northerly aspects at upper elevations will offer the best riding conditions.
Summary
Confidence
Moderate
Avalanche Summary
Numerous natural very large (up to size 3) storm and wind slabs were reported on primarily sunny aspects at treeline and above on Thursday. These avalanches were triggered by a mix of solar radiation or cornice failures.
Additionally, numerous rider triggered storm and wind slabs up to size 2 were reported on primarily sunny aspects in the alpine where the recent snow is sitting on a crust down 30-40 cm.
Snowpack Summary
Expect to find sun crust on the surface of steep, sunny aspects.
Strong solar radiation has settled the 30-50 cm of recent snow into a storm slab which has been especially reactive to human triggers on sunny aspects where it overlies a crust.
Strong southwest wind during the storm earlier in the week have added to slab formation on lee aspects at treeline and above.
The recent snow is sitting on a variety of surfaces. These include sun crust on sunny aspects and surface hoar (3-10 mm) on some shady and sheltered slopes.
The mid-snowpack is generally strong but the lower snowpack is a different story.
The November facets are still prominent at the base of the snowpack. They are showing signs of improving but this layer remains a significant concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.
Weather Summary
Friday Night
Clear skies / 10 km/h south ridgetop wind / Temperature at treeline around -9 C / Freezing level valley bottom
Saturday
Mix of sun and cloud / 10 km/h south ridgetop wind / Temperature at treeline around -3 C / Freezing level 1600 m
Sunday
Mostly sunny / 20 km/h southeast ridgetop wind / Temperature at treeline around -2 C / Freezing level 1800 m
Monday
Cloudy with isolated flurries; 0-3 cm / 20 km/h southeast ridgetop wind / Temperature at treeline around -3 C / Freezing level 1600 m
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
- Avoid exposure to slopes that have cornices overhead.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Storm slabs formed earlier in the week may continue to be reactive to human triggers at upper elevations; especially on sunny aspects.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth, but large triggers such as cornice failures or smaller avalanches in motion have the potential to produce very large avalanches with surprisingly wide propagation. Suspect terrain for human triggering includes steep, shallow, and rocky terrain where the snowpack transitions from thin to thick.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 18th, 2023 4:00PM
