Avalanche Forecast

Issued: Jan 1st, 2024 4:00PM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Persistent Slabs and Deep Persistent Slabs.

ahanna, Avalanche Canada

Purcells, East Purcell, West Purcell.

Be mindful of buried weak layers within range of human triggering.

Summary

Confidence

Moderate

Avalanche Summary

Small loose wet avalanches were reported on south aspects in the warm weather on Saturday.

Prior to the weekend, explosive-triggered wind slabs were reported to size 1.5 in the northwest Purcells and ski cuts produced loose dry to size 1 in the upper snowpack facets near Invermere.

Snowpack Summary

Various snow surfaces exist including crusts, settled powder, unconsolidated facets and old wind slab. Beneath lies a complex snowpack with many layers that vary across the region.

The most prominent is a layer of surface hoar buried 20-50 cm deep. It is less of a concern in areas where a strong, supportive crust exists above the surface hoar layer.

The lower snowpack is typically characterized by sugary, facetted crystals and a crust.

Snowpack depths at treeline average 50-120 cm with significant variability across the region.

Weather Summary

Monday night

Partly cloudy, ridgetop wind 15 km/h southeast, treeline temperature -10 °C.

Tuesday

A mix of sun and cloud, ridgetop wind 15 km/h south, treeline temperature -7 °C.

Wednesday

Mostly cloudy, ridgetop wind <10 km/h south, treeline temperature -6 °C.

Thursday

A mix of sun and cloud, ridgetop wind <10 km/h south, treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

Persistent Slabs

The primary layer of concern in much of the region is a layer of surface hoar down 20-50 cm. If triggered, avalanches on this layer could step down to deeper weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Deep Persistent Slabs

A layer of weak facets near the ground may be reactive to human triggering, especially in shallow, rocky areas in alpine terrain where the layer is not capped by a crust.