Issued: Apr 6th, 2023 4:00PM
The alpine rating is Wind Slabs and Deep Persistent Slabs., the treeline rating is , and the below treeline rating is Known problems include
Use caution on north and east slopes where strong winds are building fresh wind slabs that are possible to human trigger.
On Wednesday, storm snow continued to be reactive to natural and human triggers. A few surprise skier triggered storm slab avalanches were reported up to size 2. Naturally triggered storm slab and wind slab avalanches were observed up to size 2.5.
On Tuesday, numerous storm and wind slab avalanches were reported up to size 1.5. These failed naturally and were human-triggered.
Many of these avalanches are reported to be failing on a surface hoar layer buried near the end of March or a crust on solar aspects. Avalanche activity has primarily been observed on north and east aspects from 1700 m to 2200 m. Reports indicate that the Selkirks seem to be the most reactive with rider remote-triggered slabs in the upper 50 cm of snow. This MIN Report from Sunday indicates what is mentioned above.
Flurries Friday accumulate over 15-40 cm of settling storm snow overlying a widespread crust, except for on north-facing slopes at treeline and above, where it sits on old, faceted surfaces, and surface hoar in sheltered terrain. A surface hoar layer (down 50 cm) continues to be reactive to human triggering primarily in the Selkirks, especially on northeasterly slopes from 1700 m to 2100 m.
Strong southwest wind will build fresh wind slabs on leeward slopes and behind terrain features.
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. This layer remains a concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.
Cloudy with isolated flurries, trace accumulation. Ridgetop wind 50 km/h from the southwest. Freezing levels remain at 1700 m. Treeline high around -1°C.
Cloudy with flurries, 3-10 cm accumulation. Ridgetop wind 50 km/h from the southwest. Freezing levels 1700 m.
Flurries continue through the night, 6-10 cm of accumulation.
Cloudy with possible sunny periods and isolated flurries, 2 cm accumulation. Ridgetop wind 25 km/h gusting to 50 km/h from the southwest. Freezing levels 1600 m.
Mix of sun and cloud with isolated flurries, 3 cm accumulation. Ridgetop wind 70 km/h from the southwest. Freezing levels 2200 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Seek out sheltered terrain where new snow hasn't been wind-affected.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
With plenty of snow available for transport, strong southwest winds will build fresh wind slabs on leeward slopes Friday. Watch for the surface to become a stiffer and more cohesive slab as you move into wind exposed terrain.
Slabs may be more reactive where they sit above buried surface hoar or crust layer that exists 40-50 cm deep.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
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.
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.
Valid until: Apr 7th, 2023 4:00PM