Avalanche Forecast
Issued: Feb 21st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.
mconlan,
Avalanche Canada
Storm and wind slabs will likely be reactive to human traffic. Any incident could have serious consequences during cold weather.
Summary
Confidence
Avalanche Summary
We are receiving initial reports of widespread avalanche activity from Monday night's storm. Avalanches were small to large (size 1 to 3) and released as storm slabs, wind slabs, and dry loose, on all aspects and at all elevations.
Numerous naturally triggered large to very large (size 3 to 3.5) deep persistent slab avalanches were observed on Monday across the region. They occurred on all aspects between 1700 and 2700 m.
Looking forward, we suspect that storm and wind slab avalanches will continue to be triggerable by riders as all the recent snow slowly bonds to the snowpack. Triggering deeper layers remains possible, particularly on shallow, rocky slopes.
Snowpack Summary
Around 20 to 50 cm of snow accumulated Monday night with associated southwest wind that has now shifted to northeast wind. This snow adds to the 50 to 100 cm of snow that accumulated over the weekend. All of this snow may rest on weak surface hoar crystals at treeline elevations sheltered from the wind. Storm slabs and wind slabs exist within all this storm snow.
The mid-pack hosts various old layers of surface hoar, facets, and melt-freeze crusts that are gaining strength and bonding to the snowpack. Periodic reports of large avalanches on these layers are a reminder of the complicated snowpack in this region.
A layer of large and weak facets that formed in November is found near the base of the snowpack. The layer is slowly gaining strength but sporadic and very large avalanches continue to provide evidence that this layer cannot be trusted.
Weather Summary
Tuesday Night
Mix of sun and cloud, 20 to 30 km/h northeast wind, treeline temperature -22 °C.
Wednesday
Mix of sun and cloud with no precipitation, 20 km/h northeast wind, treeline temperature -23 °C.
ThursdayMostly clear skies with no precipitation, 20 km/h east wind, treeline temperature -24 °C.
FridayClear skies with no precipitation, 20 km/h west wind, treeline temperature -20 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Give the new snow several days to settle and stabilize before pushing into bigger terrain.
- Good day to make conservative terrain choices.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Storm Slabs
Anywhere from 20 to 50 cm of snow accumulated by midday Tuesday with southwest wind switching to northeast wind. This adds to 50 to 100 cm of snow from the weekend, which may rest on surface hoar crystals around treeline. Expect human-triggered storm slab avalanches to be likely on all aspects, particularly where it rests on surface hoar. Wind slabs are likely touchiest on south to west aspects, which is atypical.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Problematic weak layers are becoming spotty across the region, however recent large persistent slab avalanche observations continue to trickle in reminding us that these layers remain a concern.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A layer of large and weak facets sits near the base of the snowpack. This layer continues to sporadically produce very large avalanches. Human triggering is most likely in steep, shallow terrain, or by triggering a smaller avalanche that could step down to this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 22nd, 2023 4:00PM
