Avalanche Forecast
Issued: Feb 2nd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
JSmith,
Avalanche Canada
Human triggering of large storm slabs remains likely on Wednesday. Storm slabs may be surprisingly large and easy to trigger due to the presence of buried weak layers of surface hoar.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
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TUESDAY NIGHT: Flurries; 5-10 cm. / Light, west ridgetop wind / alpine low temperature -10 / Freezing level valley bottom.
WEDNESDAY: Mix of sun and cloud / Light, northwest ridgetop wind / alpine high temperature -5 / Freezing level valley bottom.
THURSDAY: Flurries; 3-5 cm. / Moderate, west ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.
FRIDAY: Mix of sun and cloud / Strong, northwest ridgetop wind / alpine high temperature -4 / Freezing level valley bottom.
Avalanche Summary
On Monday, skier triggered storm slabs to size 1.5 on surface hoar and natural storm slabs up to size 2.5 were reported in this region.
A widespread natural cycle and numerous skier triggered storm slab avalanches up size 3 were reported in this region on Sunday. These storm slab avalanches were primarily running on a weak layer of surface hoar that was buried by the recent storm. See one of several MIN reports Here and Here.
Touchy storm slabs are sitting on a very weak layer of surface hoar which is likely to be reactive to human triggers. Avalanches may be larger than expected due to the presence of this weak layer.
Snowpack Summary
20-30 cm of new snow brings recent snow totals to 50-80 cm. Rising freezing levels throughout the storm and moderate, southerly winds have caused rapid slab formation. These touchy storm slabs are sitting on multiple weak layers of surface hoar which have potential to surprise backcountry users by how easily they may be triggered and how wide the slabs propagate across slopes. The first sits below the recent snow and the second is around 50-80 cm. down.
The mid and lower snowpack is generally well settled and strong in most areas.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Be careful as you transition into wind affected terrain.
Problems
Storm Slabs
Storm slabs may be surprisingly large and easy to trigger due to the presence of buried weak layers of surface hoar.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Touchy storm slabs have recently overloaded a weak layer of surface hoar buried late January. Human triggering of this layer will remain likely where it is well preserved. The most likely places being large, open, convex slopes at treeline and below.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Feb 3rd, 2021 4:00PM
