Avalanche Forecast

On Wednesday, MINs reported touchy cut banks (MIN1), whumpfing and shooting cracks (MIN2) and reactive snowpack tests (MIN3). These reports covered a reactive layer of surface hoar below up to 40 cm of new snow, however, MIN3 also found another reactive layer of surface hoar down 75 cm. For now, we lack field observations to determine the distribution of this layer, but it is something we will be tracking.

Earlier in the week (Sunday-Monday), a few small (size 1) avalanches were reported south of Nelson. There were also reports of whumpfing and cracking suggesting the recent snow is poorly bonded to the mid-November weak layer.

Overnight snowfall accumulations ranged from 15-25 cm by Thursday morning, and upwards of 40 cm has accumulated in the last few days. In the short term, reports suggest the new snow is not bonding to a layer of surface hoar below.

Early season conditions exist with low snow amounts and under snow hazards existing at lower elevations and a deeper and drier snowpack exceeding 1 m at treeline and alpine elevations. In wind-loaded areas, snowpack heights have been reported as deep as 160 cm with windward areas scoured down to as little as 20 cm.

Up to 75 cm of snow overlies a weak layer that formed mid-November that consists of sugary faceted grains, weak surface hoar crystals in sheltered terrain features, and a hard crust on steep sun-exposed slopes. This MIN reports moderate sudden collapse results when testing this interface.

Thursday night

Cloudy with isolated flurries with trace accumulation. 10-20 km/h west wind, treeline temperatures fall below -18 °C.

Friday

Increasing clouds through the day with light flurries starting late in the afternoon. Increasing southwest wind 10-20 with gusts to 30 km/hr. Treeline temperature high -9 °C.

Gusty winds and scattered flurries overnight, 5-10 cm accumulating by Saturday morning. Southwest wind 20-35 km/hr decreasing through the day. Treeline high temperature -5 °C.

Clear, cold, and calm. Light northeast wind, treeline temperatures falling to -12 °C.

More details can be found in the Mountain Weather Forecast.

• Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
• Remote triggering is a concern, watch out for adjacent and overhead slopes.
• Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
• Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.