Avalanche Forecast

Issued: Jan 2nd, 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.

rgoddard, Avalanche Canada

Purcells, East Purcell, West Purcell.

As you move through the terrain take the time to investigate buried weak layers before choosing your lines.

Summary

Confidence

Moderate

Avalanche Summary

No new avalanches reported since this weekend.

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

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

Snowpack Summary

The surface and top layer of the snowpack are variable. It may consist of crusts, settled powder, unconsolidated facets, and older wind slabs. Beneath lies a complex snowpack with many layers that vary across the region.

The most prominent is a layer of surface hoar buried 20 to 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 to 120 cm with significant variability across the region.

Check out this blog post for some insight into the current shallow yet complex snowpack.

Weather Summary

Tuesday Night

Mostly clear with some clouds, potential trace accumulation, ridgetop winds south 15 km/h, treeline temperature -7 °C.

Wednesday

Mix of sun and clouds, trace accumulation, ridgetop winds south 10 to 20 km/h, treeline temperature -6 °C.

Thursday

A mix of sun and cloud, 2 cm accumulation, ridgetop winds south-southwest 10 to 15 km/h, treeline temperature -7 °C.

Friday

Cloudy with late-day clearing, 2 cm accumulation, ridgetop winds southwest 10 km/h, treeline temperatures -8 °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 to 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 the alpine where the layer does not have a thick crust above it.