Avalanche Forecast

Issued: Dec 18th, 2013 4:25PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Basal weaknesses are waking up with the added snow load. Avalanche control today produced large, destructive avalanches. Use caution in avalanche terrain!

Summary

Weather Forecast

Cooling temps (-15 to -25) and clearing skies for Thursday. Possibly some light precipitation on Friday/ Saturday. Light SW/W winds throughout the period

Snowpack Summary

Another 10-20 cm of new snow today brings the storm snow total to 40-60 cm. Moderate to strong winds have created touchy windslabs in the alpine and at treeline. Basal facets, depth hoar and the october rain crust are prominent at the base of the snowpack.

Avalanche Summary

Avalanche control work today on the Sunshine road produced large avalanches (size 2.5-3) on 6 of 9 shots. These avalanches appeared to initiate in the storm snow and step down to the October crust. Similar reports from the Sunshine avalanche control team and a report of a size 2.5 natural near Bow Summit indicate widespread instability.

Confidence

Problems

Wind Slabs

40-60 cm of storm snow has created touchy wind and storm slabs which are easily triggered and will likely step down to the basal weak layers.

Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.Good day to make conservative terrain choices.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

The deep persistent weak layers (facets, depth hoar, and october rain crust) are waking up with the added load. Triggering this layer is likely and will result in large, destructive avalanches as seen in avalanche control work today.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 19th, 2013 4:00PM