Avalanche Forecast

Issued: Jan 26th, 2017 4:24PM

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

Avalanche Canada triley, Avalanche Canada

Developing avalanche danger is expected to reach HIGH in the alpine on Friday. If the storm arrives early danger may reach HIGH at all elevations.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Stormy weather for the next few days. Overnight: Extreme southwest winds combined with 10-20 cm of new snow and freezing levels around 800 metres. Friday: Extreme south winds, 20-30 cm of new snow during the day and another 20-40 cm overnight, freezing level 1000 metres. Saturday: another 25-40 cm of new snow combined with extreme south winds and freezing levels rising to 1500 metres. Sunday: Winds becoming moderate to strong southwest combined with 10-20 cm of new snow and dropping freezing levels.

Avalanche Summary

No new avalanches reported. One report on Wednesday of a skier triggered wind slab size 1.0 on a convex roll at 1500 metres that was about 25cm deep. Expect avalanche size and frequency to increase as the forecast storm moves into the region.

Snowpack Summary

There is 10-20 cm of new snow above the latest buried surface hoar layer from January 23rd that has been found up to size 10 mm at treeline and below. This surface hoar layer may be associated with a crust below 1100 metres. There continues to be several other surface hoar layers of concern from early January and Christmas. Some reports show these persistent weak layers to be rounding and bonding, however we are still getting some reports of sudden planar releases in snowpack tests with hard forces applied. I suspect the forecast heavy precipitation over the next few days will be a good test for these older buried weak layers.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs are expected to develop with forecast new snow and wind. Avalanche size and frequency will increase with each pulse of precipitation, increasing winds, and rising freezing levels.
Minimize exposure during periods of heavy loading from new snow, wind.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
It may still be possible to trigger avalanches on buried weak layers (Dec 25, Jan 5th, Jan 12th surface hoar) ...or have a smaller avalanche 'step down' and trigger one of these layers. The new storm will be a good test for these weak layers.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.Be aware of the potential for wide propagations due to the presence of buried surface hoar layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Jan 27th, 2017 2:00PM