Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
The avalanche cycle and the period of highest danger is past its peak, but now comes the hardest part for backcountry recreation: human triggering remains very likely, but not as obvious. The Feb 3 interface is pervasive, and producing large avalanches and close calls throughout the Rockies. Avoid avalanche terrain.
Confidence
High
Avalanche Summary
Several natural avalanches up to size 3 were observed in the alpine on Monday that occurred in the previous 12 hrs, likely on the Feb 3 interface.
Explosive control produced avalanches from size 1-3 in various places on Monday at all elevations.
These avalanches were failing on storm interfaces as well as the Feb 3 interface and occasionally the deep persistent layers.
Several close calls with human triggering of avalanches from size 2-3 have occurred in the past three days.
Snowpack Summary
50-90 cm of new snow fell from Feb 23 to March 2 and is now being blown into wind slabs at upper elevations by strong westerly winds overnight Monday. These easily triggered slabs overlie the weak Feb 3 facet/crust layer that is down 50-90 cm and exists up to 2500 m and higher on solar aspects. The lower snowpack consists of several facet layers and depth hoar and the base of the snowpack is weak in shallow areas.
Weather Summary
Although a clearing trend is underway this week, strong (50 km/hr) upper-level winds are forecast from the west overnight Monday, through Tuesday. Other than the wind (which matters a lot), the weather improves as a ridge of high pressure establishes itself. For Tuesday expect trace amounts of snow, broken skies and temperatures of -10 to -20; same for Wednesday and full clearing by Thursday.
Terrain and Travel Advice
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
- Remote triggering is a big concern, be aware of the potential for wide propagations and large, destructive avalanches at all elevations.
Avalanche Problems
Wind Slabs
Recent storm snow is being redistributed into leeward areas by strong winds overnight on Monday and into Tuesday. Look for locally deep deposition areas and avoid them - human triggering is very likely right now.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Very Likely
Expected Size: 1 - 2.5
Persistent Slabs
50-90 cm of snow overlies the weak Feb 3 crust/facet interface. Numerous natural and skier-triggered avalanches have occurred on this interface. Wide propagations and remote triggering remain likely on this layer. Avoiding avalanche terrain is the only reliable way to deal with this layer .
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 2 - 3.5
Deep Persistent Slabs
Some recent avalanches are stepping down to the weak basal facet and depth hoar layers near the ground resulting in large avalanches. This seems to be most common in thin, steep, rocky terrain in the alpine. Recent snow loading has made this layer more sensitive to natural and human triggering.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 2 - 3.5