Avalanche Forecast
Issued: Dec 2nd, 2020 4:03PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs and Wind Slabs.
Ian Jackson,
Lots of good observations today, and overall the sun didn't destabilize the snowpack as much as we thought it might have. Thursday and Friday look cooler, but still a good idea to minimize your exposure to steep solar terrain in the heat of the day.
Summary
Weather Forecast
The alpine inversion (warmer temperatures in the alpine than the valley bottom) will continue on Thursday but be less severe. Winds are forecasted to pick up Thursday afternoon, and temperatures will cool further on Friday (although remain warm). No precipitation forecast in the next 3 days. Overall, mild and dry conditions.
Snowpack Summary
Variable surface conditions exist with hard wind slabs in exposed locations, softer snow in more sheltered areas and a surface crust on some solar aspects. The Nov 5 facet/crust combo is down 50-80 cm and producing hard to no results. This crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 70-140 cm.
Avalanche Summary
Despite warm alpine temperatures and sun, very little activity was noticed on Wednesday. Some small wet loose pinwheeling up to size 1 out of steep solar terrain in the afternoon, but overall fairly minimal activity with lots of good observations in the southern Wapta / Yoho Valley area.
Confidence
Timing or intensity of solar radiation is uncertain
Problems
Deep Persistent Slabs
The Nov 5 crust has facets above and below it, and exists up to 2500m on shady aspects and higher on solar aspects. We have seen a few isolated avalanches on this layer so use caution in large steep terrain features during warm sunny periods.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
- Be aware of thin areas that may propogate to deeper instabilites.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
These wind slabs are slowly bonding, but may still be a problem in steep alpine terrain where the surface looks wind affected.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 3rd, 2020 4:00PM
