Avalanche Forecast

Issued: Feb 20th, 2014 5:50PM

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

tim haggarty, Parks Canada

Waterton Lakes.

The widespread Natural activity that we have seen this week should start to diminish as the last of the storms pass. Human triggering will continue to be likely and conservative travel is advised. The CAC has posted SPECIAL PUBLIC AVALANCHE WARNING.

Summary

Weather Forecast

The system over Waterton will pass overnight leaving another 10cm with moderate West winds. Small amounts of snow are expected Friday as the winds start to shift NW and temperatures begin to drop. Light North winds for Saturday with some flurries as the temperatures continue to drop. Expect -20 C for Monday with very light winds and blue skys.

Snowpack Summary

Up to 100 cm now buries a significant weak layer found on all aspects and at all elevations. Gusty West winds and mild temperatures have contributed to widespread slab formation especially in open areas. More loading and wind will increase the serious nature of these persistent slabs. Weak snow at the base of the snowpack also remains a concern.

Avalanche Summary

Widespread natural activity occurred though the week with many large events flattening trees. Most significant paths ran. One sz 3.5 avalanche was confirmed to have stepped down to the November facets and this is suspected to have occurred in some of the many other sz 3 events which ran full path. Impressive propagations and remote triggering seen.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

These recently formed slabs have proven to be very easy to trigger failing naturally and with light loads. Limit your exposure to significant slopes. Do not get taken by surprise by the long propagations or remote triggering that has been seen.

Avoid open slopes with any steepness over 30 degrees.Use conservative route selection, stick to moderate angled terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

Do not forget that there is weak snow under the entire snowpack. In shallow areas this faceted snow has continued to weaken and the slab above it that is holding the snowpack together has become stressed by recent loading to the point of failure.

Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Feb 23rd, 2014 4:00PM