Large and destructive human-triggered avalanches are still possible. Remain suspicious of steep, unsupported slopes at treeline and in the alpine.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Very light flurries and a mix of sun and cloud are expected for the forecast period as a ridge of pressure remains parked over the province. Alpine winds will be moderate to strong from the northwest on Tuesday. On Wednesday and Thursday the winds should be generally light from the southwest. Alpine temperatures should hover at about -12 on Tuesday, rising slightly for Wednesday and Thursday. No significant snowfall is expected until Friday.
Avalanche Summary
Avalanche observations have been extremely limited, although explosives testing produced a couple of size 1.5 slab avalanches in the north of the region. These avalanches occurred at about 2000m and failed on one of the November persistent weaknesses. Avalanche activity on these deep layers is expected to become less frequent, although the potential consequences of a release continue to be severe.
Snowpack Summary
Recent strong and variable winds may have redistributed surface snow creating new wind slabs in exposed high elevation terrain. Recent rain and cooling have created a near-surface crust that extends to about 1900m. Approximately 100cm below the surface you'll likely find weak crystals which formed throughout early and mid-November. These weak crystals include facets on a hard rain crust, and surface hoar (which may also sit on a crust on steep southerly slopes). Snowpack tests on Sunday in Rogers Pass suggest the layers can still be human triggered, and if triggered, are capable of producing wide propagations and large avalanches.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.