Avalanche Forecast

Issued: Feb 20th, 2017 4:59PM

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

triley, Avalanche Canada

South Rockies.

Forecast new snow and wind will elevate the avalanche danger on Tuesday.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

Tonight: 5-8 cm of new snow combined with strong southwest winds and overnight freezing down to valley bottoms. Tuesday: 3-5 cm of new snow with moderate westerly winds and daytime freezing up to 1500 metres. Wednesday: Chance of flurries with moderate southwest winds and alpine temperatures around -8. Thursday: 3-5 cm of new snow with light northeast winds and alpine temperatures around -15.

Avalanche Summary

Forecast new snow and wind may develop new storm slabs at treeline and above. These new storm slabs may not bond well to the old surface crust. Also keep in mind that the deep persistent slab problem is a low probability/high consequence scenario that warrants extra caution around large open slopes, especially in shallow snowpack areas.

Snowpack Summary

Forecast new snow and wind may develop new storm slabs. These new storm slabs may add to the recent snow that sits above a thick rain crust below 1900 m. A stiff midpack sits above weak sugary snow near the ground. This deep persistent weakness is primarily a concern in shallow snowpack areas. Watch this video from the South Rockies field team for some recent test results on this layer.

Problems

Deep Persistent Slabs

A weak layer near the base of the snowpack has the potential for large avalanches, especially in areas with minimal rider compaction or thin variable snow cover.

Avoid lingering in runout zones.Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Storm Slabs

Forecast new snow and wind are expected to develop new storm slabs on all aspects. These thin new slabs may be easy to trigger and may slide fast and far due to the underlying crust.

Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with elevation.On steep slopes, pull over periodically or cut into a new line to manage sluffing.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 21st, 2017 2:00PM