Avalanche Forecast
Issued: Mar 3rd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
There is a high degree of variability through the region. Avalanche danger is highest in the north and west where a persistent weak layer is active and overnight snow and wind are forming fresh and reactive wind slabs. In drier eastern areas, avalanche danger may be a step lower.
Summary
Confidence
Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.
Weather Forecast
Tuesday night: 10-15 cm new snow in the north of the region, trace elsewhere. Strong west wind. Freezing level 1400 m.
Wednesday: Up to 5 cm new snow. Moderate to strong northwest wind. Freezing level 1000 m.
Thursday: Flurries. Moderate southwest wind, strong at ridgetop. Freezing level 1700 m.
Friday: 5-15 cm new snow. Light southwest wind. Freezing level 1500 m.
Avalanche Summary
Over the weekend and through Tuesday, natural and skier triggered wind slabs size 1-1.5 were observed.Â
Persistent slab avalanche activity is starting to pick up in the west of the region, were snowfall amounts have been greatest over the surface hoar layer which is now reaching a tipping point. In this part of the region on Sunday, skier accidental persistent slabs size 1-2 were reported on east aspects treeline and below. Heli remotes were reported up to size 2.5. Natural persistent slabs 2-3 were observed on south aspects around treeline.
Snowpack Summary
Light overnight snowfall and strong winds are building fresh wind slabs in the alpine and open areas at treeline.
A weak layer of surface hoar sits 20-60 cm deep. The overlying snow has been cohered into slabs by incremental loading through successive storms, wind at upper elevations and mild temperatures at lower elevations. As slab character increases, so do reactivity and size of avalanches failing on the weak layer (surface hoar). Read more about surface hoar on our forecaster blog!
Deep basal facets lurk near the bottom of the snowpack. This layer has been responsible for occasional and hard to predict deep persistent slab avalanches usually triggered from shallow, rocky start zones. No activity has been observed on these layers in the past week.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
Light overnight snowfall and strong winds are building fresh wind slabs in the alpine and open areas at treeline. Wind slabs will be deepest and most reactive in the north of the region, where up to 20 cm of new snow fell overnight. If triggered, windslabs have the potential to trigger deeper weak layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar sits 20-40 cm deep. So far, the layer has been most reactive at treeline and alpine elevations in the deeper snowpack areas in the west of the forecast region. Avalanche activity on this layer is expected to increase as it approaches critical loading by new snow and wind forecast later in the week. Read more about surface hoar on our forecaster blog!
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Weak snow at the bottom of the snowpack continues to pose a deep persistent slab avalanche problem. Treat wind scoured, rocky, shallow terrain as suspect. Also avoid big alpine slopes that are threatened by cornices overhead.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 4th, 2020 5:00PM
