Avalanche Forecast

Issued: Dec 12th, 2016 4:00PM

The alpine rating is low, the treeline rating is low, and the below treeline rating is low. Known problems include Loose Dry and Deep Persistent Slabs.

grant statham, Parks Canada

Banff Yoho Kootenay.

Back in the deep freeze for the rest of the week. Low danger continues, although the weakening surface snow is resulting in some large sluffs. Strong temperature gradients in the snowpack are weakening it rapidly - look here for today's snow profile.

Summary

Weather Forecast

Severe clear and cold for the week - with a brief burst of snowfall on Thursday as the edge of the arctic air moves through town and back again. Expect Tuesday's temperatures to range from -15 to -25 and some forecasts are showing NW winds rising in alpine areas. Look for sunny, sheltered locations to stay warm - its really cold out there!

Snowpack Summary

5 cm of new snow overlies a mostly facetted snowpack that is growing weaker each day with these cold temperatures. Profiles today near Sunshine showed loose facets in the upper 30 cm, which have no cohesion and are creating the Loose Dry problem. Also 40 cm above the ground is the Nov 12 crust, also growing weaker each day.

Avalanche Summary

No significant slab avalanches reported or observed in the past 5 days, but loose dry skier triggered avalanches in steep terrain have been reported in several locations over the past few days. This is a result of the surface faceting that is occurring under these cold temperatures as the surface snow weakens and looses cohesion.

Confidence

Intensity of incoming weather systems is uncertain on Thursday

Problems

Loose Dry

The surface snow is faceting rapidly and becoming weak, resulting in large sluffs developing in steep and/or confined terrain. Be very wary of your exposure above and below, and remember to ski off fall line to manage any sluffs growing behind you.

On steep slopes, pull over periodically or cut into a new line to manage sluffing.Be aware of party members below you that may be exposed to your sluffs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

The Nov 12 crust has weak snow all around it, and is a suspect and dangerous layer. Although it's reactivity seems to have abated during the current cold snap, we expect it to awaken again with additional load and warmer temperatures (one-day).

Avoid shallow snowpack areas where triggering is more likely.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 13th, 2016 4:00PM