Avalanche Forecast
Issued: Jan 21st, 2020 4:13PM
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.
snow safety,
Parks Canada
Deep persistent slab avalanches can still be triggered with large loads such as cornices.
Summary
Weather Forecast
Temps are going to dip slightly tomorrow by a few degrees. By Friday temps should be back where they are today. Up to 5cm of new snow is expected tomorrow and up to 15cm by Friday afternoon. Wind will predominantly be from the SW during this period and varying between moderate and strong.
Snowpack Summary
Wind effect and isolated windslabs exist in lee areas in the alpine from recent loading. There is 40-60 cm above the Dec 31 layer of facets, surface hoar and sun crust which is slowly becoming less reactive. Concern remains for the weak layers of facets and depth hoar near the base of the snowpack.
Avalanche Summary
Explosive control on highway 93N today produced a size 3.5 deep persistent slab on Bison peak. Forecasters were targeting shallow areas in the start zones hoping for the widest propagations. Other explosive controlled avalanches were produced up to size 2.5 on the same control run. Not recent natural activity was observed.
Confidence
Problems
Wind Slabs
Wind slabs were less reactive today, even with explosive control. Isolated pockets of wind still exist in lee areas.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Use caution in lee areas. Recent wind loading has created wind slabs.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
The late Dec layer of surface hoar, facets or sun crust is buried 40-60cm throughout the region and producing variable results depending on location and what crystal form is present. There is still high uncertainty as to how reactive this layer is.
- If triggered the persistent slab may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
We have seen a few recent avalanches on the deep persistent problem of basal facets and depth hoar, often beginning as wind slabs and then stepping down to the weak base. Conservative terrain choice is your best defence.
- Avoid shallow snowpack areas where triggering is more likely.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 22nd, 2020 4:00PM
