Avalanche Forecast
Issued: Feb 20th, 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
30 to 50 cm of snow is forecast Monday night into Tuesday morning, which is likely to trigger an avalanche cycle that could reach valley bottom. Travel in avalanche terrain is not recommended.
Summary
Confidence
Moderate
Avalanche Summary
Many small to large (size 1 to 2.5) storm slabs and wind slabs were trigered naturally, by exlosives, and riders on Sunday. They generally occurred at treeline and alpine elevations and on all aspects. They were mostly 10 to 50 cm deep, within and at the base of the recent storm snow.
The most recent persistent slab avalanche was reported on Friday, occurring near Revelstoke at 1500 m on a northwest aspect. The avalanche likely released on an old facet and/or surface hoar layer above a melt-freeze crust from late December.
The most recent deep persistent slab avalanche activity was between February 13 and 16, with most avalanches occurring at treelin and alpine elevations on all aspects.
Looking forward, a widespread avalanche cycle is anticipated on Monday night into Tuesday. Human-triggered avalanches are likely for Tuesday. Resulting avalanches could travel to valley bottom. Travel in avalanche terrain is not recommended.
Snowpack Summary
Around 30 to 50 cm of snow is forecast for Monday night into Tuesday, building on the 50 to 100 cm of recent storm snow across the region. All this snow overlies previously wind affected snow in wind-exposed terrain and surface hoar crystals in wind-sheltered terrain around treeline elevations. Wind slabs are likely forming on all aspects at higher elevations from southwest wind switching to northeast wind.
The mid-pack hosts various old layers of surface hoar, facets, and melt-freeze crusts that are slowly bonding to the snowpack. Reports of periodic 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 very large avalanches continue to provide evidence that this layer cannot be trusted.
Weather Summary
Monday Night
Cloudy with snowfall, accumulation 20 to 40 cm, 20 to 40 km/h southwest wind, treeline temperature -7 °C.
Tuesday
Mostly cloudy with snowfall, accumulation 5 to 15 cm, 20 km/h northeast wind, treeline temperature -16 °C.
WednesdayMix of sun and cloud with no precipitation, 20 km/h east wind, treeline temperature -22 °C.
ThursdayMostly clear skies with no precipitation, 20 km/h east wind, treeline temperature -24 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Travel in alpine terrain is not recommended.
- Very large and destructive avalanches could reach valley bottom.
Problems
Storm Slabs
Rapid snowfall and strong wind will likely trigger a natural avalanche cycle on Monday night into Tuesday morning. Human-triggering is likely to extend over the course of the day.
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. Rapid loading could be the tipping point for them.
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, and Monday night's storm will increase the likelihood of avalanches occurring. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain, or by triggering a smaller avalanche that could step down to this layer. Resulting avalanches are anticipated to reach valley bottom.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 21st, 2023 4:00PM
