Avalanche Forecast

Issued: Dec 22nd, 2017 4:28PM

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

shorton, Avalanche Canada

Lizard-Flathead.

Deep powder offers excellent riding in many areas, but there's a highly variable weak layer that warrants cautious terrain choices. Read this forecasters' blog for more details.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

SATURDAY: Dry and sunny, moderate northwest winds, temperatures around -15 C.SUNDAY: Sunny with increasing clouds, light northwest winds, temperatures around -15 C.MONDAY: Mix of sun and cloud, light northwest winds, temperatures around -18 C.

Avalanche Summary

A natural avalanche cycle was observed in alpine terrain on Friday with storm slabs up to size 2 (typically 20-40 cm deep). Explosive avalanche control triggered similar sized avalanches.

Snowpack Summary

Around 50 to 80 cm recent new snow now rests on a variety of old surfaces. These old surfaces include crusts on south through west facing slopes, wind-scoured slopes and, in sheltered terrain at and below treeline, large feathery surface hoar crystals. Lower in the snowpack, you should be able to find a hard crust that was buried near the end of November. This crust is approximately 30 cm thick and extends from 1600 m to mountain top on all aspects. Average snowpack depths at treeline in the region range from 100 to 140 cm.

Problems

Wind Slabs

Low density snow and sustained alpine winds are a recipe for touchy wind slabs in exposed terrain.

Use ridges or ribs to avoid pockets of wind loaded snow.Avoid freshly wind loaded features.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

A variable weak layer buried approximately 60 cm below the surface will likely remain sensitive to human-triggered avalanches in areas with stiffer snow. Sheltered areas with steep, unsupported terrain are the most likely places to be caught.

The new snow will require several days to settle and stabilize.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Dec 23rd, 2017 2:00PM