Avalanche Canada jsmith, Avalanche Canada

South Rockies Avalanche Forecast

Mar 10th, 2018 4:30PM

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

Deeply buried weak layers are lingering near the base of the snowpack. These layers are most likely to be triggered from thin or variable snowpack areas or with a large load like a cornice fall.

Summary

Confidence

High -

Weather Forecast

SUNDAY: Sunny / Light southwesterly ridgetop winds / Freezing level rising to around 2300 m.MONDAY: Sunny / Light southwesterly ridgetop winds / Freezing level rising to around 2400 m.TUESDAY: Sunny / Light southwesterly ridgetop winds / Freezing level rising to around 3000 m.

Avalanche Summary

Several human triggered wind slabs up to size 1.5 were reported on northeasterly slopes on Friday.  Explosive control work northwest of Elkford on Tuesday produced numerous size 3 persistent slab avalanches failing on facets near the base of the snowpack. The most notable results were on steep, rocky north aspects, and lower angled west aspects.

Snowpack Summary

Up to 20 cm of recent storm is rapidly settling. This snow overlies decomposing previous storm snow, old wind slabs, and sun crust on solar aspects. Cornices are large and prone to failure over the weekend due to forecast sunny skies and rising freezing levels.The upper/mid-pack is generally well settled and strong.The lower snowpack is weak with a combination of crusts and facets near the bottom of the snowpack that are widespread. The primary concern looking ahead is the potential of these deeper persistent weak layers becoming active by rapid warming of the snowpack through rising freezing levels and intense solar radiation. This is most likely to occur on steep south facing slopes.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3.5
Deeply buried weak layers are lingering near the base of the snowpack. These layers are most likely to be triggered from thin or variable snowpack areas or with a large load like a cornice fall.
Avoid steep, rocky, and shallow snowpack areas where triggering is more likely.Steep south facing slopes are the most likely to trigger.

Aspects:

All aspects.

Elevations:

All elevations.

Cornices

An icon showing Cornices

Likelihood

Possible

Expected Size

1.5 - 3
Daytime heating and solar radiation will weaken cornices making them more prone to failure. Falling cornices may trigger large avalanches on deeply buried weak layers.
Limit your exposure to cornices overhead.Give cornices a wide berth while traveling on ridge-tops.

Aspects:

North, North East, East, South East, South.

Elevations:

Alpine, Treeline.

Loose Wet

An icon showing Loose Wet

Likelihood

Possible

Expected Size

1 - 2
Forecast sunshine may trigger loose wet avalanches on steep south facing slopes.
Start early to staff off south facing slopes during the heat of the day.Watch for signs that the snow is heating up such as pin-wheeling and point-releases below cliffs.Avoid terrain traps such as gullies and cliffs where small avalanches can have high consequence.

Aspects:

North, North East, East, South East, South.

Elevations:

All elevations.

Valid until: Mar 11th, 2018 3:00PM