Avalanche Forecast
Issued: Feb 25th, 2020 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.
ahanna,
Avalanche Canada
Avalanche danger will be a step higher in the south half of the region where storm slabs are deeper, more wind-affected and may sit over a weak layer.
Summary
Confidence
Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.
Weather Forecast
Tuesday night: Scattered flurries bringing a few cm of new snow. Southwest wind light in the north, moderate to strong in the south. Freezing level 1000 m.
Wednesday: Isolated flurries. Light southwest wind. Freezing level 1300 m.
Thursday: Mix of sun and cloud. Light to moderate southwest wind. Freezing level 1500 m.
Friday: Mix of sun and cloud. Light to moderate southwest wind. Freezing level 1600 m in the north, 2000 m in the south.
Avalanche Summary
Natural wind slab avalanches were observed on northeast to west aspects in the alpine size 1.5-2, as well as skier controlled size 1-1.5 out of wind loaded pockets. Reports of avalanche activity over the weekend were limited to loose dry and soft slab avalanches to size 1.5 in the north of the region
Snowpack Summary
15-30 cm of recent snow, and as high as 50 cm in the Coquihalla, may overly isolated patches of surface hoar in sheltered areas at low elevations or sun crusts on solar aspects. In parts of the region that did not receive wind, the snow remains low density and evenly distributed all except exposed ridgetops. In windier areas, deep wind loaded pockets have been observed in lee features in the alpine.
In the north part of the region (e.g. Duffey/Hurley/Goldbridge), a deep instability exists in the snowpack, consisting of a weak basal facet-crust complex. Sporadic avalanche activity on this layer is keeping it on our radar, with the latest report described here. In the south of the region, including the Coquihalla and Manning areas, there are no concerns about deeply buried weak layers.
Terrain and Travel
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
Problems
Storm Slabs
15-30 cm of recent snow, and as much as 50 cm in the Coquihalla, may overly isolated patches of surface hoar in sheltered areas at low elevations or sun crusts on solar aspects. In the north of the region, the problem has been isolated to wind slab in the alpine. The Coquihalla received more snow and wind, and we still have uncertainty around the distribution and sensitivity of the weak interface. We anticipate the problem to extend into all elevation bands in this part of the region.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
In the north of the region (e.g. Duffey, Hurley, Goldbridge), a buried weak layer lingers at the base of the snowpack. The most likely place to trigger this layer is in shallow and rocky terrain. This layer has been quiet, with no reports of avalanches on it since early February. There is potential for it to wake up with rapid warming or significant loading by new snow.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 26th, 2020 5:00PM
