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; 3-10 cm. / Moderate, west ridgetop wind / alpine low temperature -10 / Freezing level valley bottom.
WEDNESDAY: Mix of sun and cloud / Light, northwest ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.
THURSDAY: Cloudy / Moderate, west ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.
FRIDAY: Cloudy / Moderate, northwest ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.
Avalanche Summary
On Tuesday, several skier triggered storm slabs up to size 2 and numerous explosive triggered storm slabs up to size 3 were reported near Golden.
Check out this MIN on the 29th and this MIN on the 28th from near Kicking Horse.
Touchy storm slabs are sitting on a 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
15-25 cm. of new snow brings recent snow totals to 40-50 cm. The recent snow fell with warm temps and moderate southerly winds, both of which increased slab development and reactivity within the new snow. This recent snow may be sitting on top of a layer of surface hoar which would greatly increase the reactivity of the newly formed slabs to human triggers, as well as the size of avalanches. However, the size and distribution of this layer is uncertain.Â
50-90 cm. down is an older surface hoar and/or a thin melt crust from mid January. This layer was more prominent in the north Purcells in sheltered, open slopes at treeline and may become reactive with the recent snow load.
Two deeper layers persist, though they have been recently unreactive. Down 100-150 cm lies the December weak surface hoar / crust / facet layers. Closer to the ground lies the early November crust facet complex. Though unlikely to trigger, caution for these layers remains with large loads in steep, shallow, rocky areas with a thin to thick snowpack or shallow areas below treeline. Â
Terrain and Travel
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- In times of uncertainty conservative terrain choices are our best defense.
- 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.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Storm Slabs
40-50 cm of recent snow has formed reactive storm slabs sitting on a weak layer of surface hoar. These slabs may be especially reactive in wind affected terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar buried mid January is down 40-120 cm and may be found on sheltered slopes near treeline in northern parts of the region. Deeper layers from early December and November can still be found in the snowpack. These layers may become reactive with additional snow load or in shallow, rocky, or thin to thick snowpack areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 3rd, 2021 4:00PM
