Avalanche Forecast

Issued: Jan 16th, 2018 5:47PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Persistent Slabs and Wind Slabs.

simonhorton, Avalanche Canada

South Rockies.

The snowpack still needs more time to heal. Patience and conservative terrain choices are critical.

Summary

Confidence

High - Freezing levels are uncertain

Weather Forecast

WEDNESDAY: Mix of sun and cloud, moderate southwest winds increasing throughout the day, freezing level around 1500 m.THURSDAY: Light flurries with up to 5-15 cm of new snow, strong southwest winds, cooling throughout the day with freezing level around 1300 m.FRIDAY: Light flurries, strong southwest winds, alpine temperatures around -5 C.

Avalanche Summary

Large persistent slab avalanche were observed north of Sparwood (see the report here), which likely occurred over the weekend. Otherwise, limited reports suggest wet loose avalanches have been running in steep solar terrain and small thin wind slabs (size 1-1.5) releasing in alpine terrain.

Snowpack Summary

Warm temperatures have settled the snow and left moist snow and thin crusts on the surface of solar aspects. An unstable weak layer from mid-December (predominantly feathery surface hoar crystals and/or a sun crust) is found at treeline and below treeline elevations. Slabs can fail easily on this layer, either naturally or with the weight of a person or machine. Deeper in the snowpack, an early-season rain crust and sugary facets exist. An avalanche in motion could step down to these deeper layers, creating a large and destructive avalanche. The snowpack is variable across the region, but persistent slabs are generally a widespread problem. Wind slab distribution will be more variable. New wind slabs can be found in parts of the region due to recent southwest winds. Windward alpine slopes may be scoured; and variable wind slabs are found at treeline and alpine elevations. Snowpack depths are variable across the region and typically shallower in the east.

Problems

Persistent Slabs

Large avalanches may be triggered on a number of buried weak layers, even in fairly dense trees and shallow slope angles.

Avoid open slopes and convex rolls where buried weak layers may be preserved.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Stick to simple terrain and be aware of what is above you at all times.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

Wind Slabs

Recent variable winds have redistributed loose snow into wind slabs on a range of aspects at higher elevations. A big enough wind slab release in the wrong location may have the force needed to trigger a deeper persistent weak layer.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Jan 17th, 2018 2:00PM