Avalanche Forecast
Issued: Mar 1st, 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
Avalanche danger will be one step lower in the central part of the region where less than 10 cm of snow fell on the weekend. Recent snow has been blown into wind slabs which may sit over a weak layer. Watch for signs of instability as you travel.
Summary
Confidence
Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.
Weather Forecast
Sunday night: Cloudy periods. Moderate to strong northwest wind, extreme at ridgetop by early morning. Freezing level 500 m.
Monday: Flurries bringing up to 5 cm new snow. Strong northwest wind. Freezing level 1400 m.
Tuesday: 5-15 cm new snow overnight. Moderate southwest wind. Freezing level 1700 m.
Wednesday: 10-20 cm new snow. Moderate west wind. Freezing level 1200 m.
Avalanche Summary
On the weekend, natural, skier and snowmobile triggered storm and wind slab avalanches were reported size 1-2.Â
A few skier triggered avalanches have been associated with the persistent surface hoar problem. Activity on this layer is expected to increase with additional snow loads forecast later in the week.
Snowpack Summary
Recent wind has redistributed surface snow in the alpine and exposed treeline, loading snow into lee terrain features. Fresh wind slab development will be deepest and most reactive in the north of the region, where 20 cm of snow fell on the weekend.
A weak layer of widespread surface hoar sits 20-40 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.
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.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Problems
Wind Slabs
Fresh snow will be touchiest where wind affected. New snow with be easily transported by moderate to strong winds overnight building fresh windslabs.
These windslabs will overlay a variety of surfaces including buried windslabs, meltfreeze crusts, or buried surface hoar.
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 2nd, 2020 5:00PM
