Avalanche Forecast

Issued: Apr 16th, 2014 4:00PM

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

Aaron Beardmore, Parks Canada

Banff Yoho Kootenay.

A large avalanche (skier remote) was triggered on Mt. Whymper yesterday. This was regarded as an anomaly. Deep persistent slab avalanches are still possible. Continue to make judicious terrain choices as the spring conditions set in.

Summary

Weather Forecast

Cloudy skies and light precip is forecasted for the region. Generally, there will not be enough accumulation to alter the danger rating. The first increase in temperature is forecasted on Saturday. If this comes to fruition, expect a major cycle with large avalanches running on the basal facets.

Snowpack Summary

A supportive melt-freeze crust exists on all aspects to 1900m and higher on south and west aspects. Dry snow exists on N/NE aspects above this. The snowpack is well settled with no surface instabilities. The deep persistent weak layers are dormant, but may awaken if it warms up. As demonstrated yesterday on Mt. Whymper, (see avalanche table).

Avalanche Summary

Forecasters were very surprised yesterday after hearing a report of a size 3.5 skier remote avalanche on Mt. Whymper. The group heard a whumph and 30 seconds later the slide released taking out the whole slope the party had just climbed up from 70m away. Dimensions: 400m wide x 100cm deep x 1000m long. Reminder, nothing is certain. Picture

Confidence

Problems

Deep Persistent Slabs

As yesterdays avalanche on Mt Whymper demonstrates, large avalanches are still possible. While this is not a widespread problem, deep basal layers are still susceptible to human triggering.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Wet

Hot temperatures will be the incentive for this problem to become more active. A quick blast of solar energy on south aspects at low elevations will be all it takes to get the snow moving.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 17th, 2014 4:00PM