Avalanche Forecast

Issued: Jan 27th, 2015 9:43AM

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

jlammers, Avalanche Canada

Northwest Inland.

The storm may have tapered-off, but persistent weaknesses have to the potential to surprise with nasty consequences. Conservative terrain selection remains critical.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Generally light snowfall, strong southwest winds and freezing levels at 600m are expected on Wednesday. Snowfall is expected to intensify Wednesday evening and continue throughout Thursday. By Friday morning, we can expect up to 15cm of accumulated snowfall. Winds are forecast to remain strong and southwesterly during the system, and then become light and northwesterly as the snowfall tapers-off on Friday. Freezing levels should hover around 800m for Thursday and Friday.

Avalanche Summary

A few close calls on Sunday suggest that the region has undergone a fairly active avalanche pattern. In the Hankin area, a skier accidentally triggered a size 2.5 avalanche which resulted in a full burial and minor injuries. The avalanche was reported to have occurred on a wind-loaded, north-facing slope. The avalanche initially failed on the January crust/surface hoar combo, and then stepped-down to the November crust and basal facets. Thanks to the party involved for sharing this information, and good work on a quick and effective companion rescue.On the same day in the Sinclair area, a snowmobile may have been the trigger for a size 3 avalanche. The avalanche had a crown between 1 and 2 metres, and propagated up to 200 metres wide.Â It occurred on a wind-loaded, north-facing alpine slope and may have failed on the November crust facet combo. Given the persistent nature of these weak layers, there is ongoing potential to trigger these deeper, destructive layers.

Snowpack Summary

Moderate to heavy snowfall (with rain at lower elevations) and strong southwest winds have built deep and dense storm slabs. These storm slabs are expected to be most reactive in wind-exposed, upper elevation terrain. A rain crust and/or surface hoar layer buried mid-January may be found between 60- 100cm below the surface. This persistent weakness has been reactive with recent storm loading. Near the base of the snowpack is the crust-facet combination buried in November. This deep persistent weakness seems to have "woken-up" in some terrain in response to warming and heavy loading from wind and snow.

Problems

Persistent Slabs

Recent avalanche activity indicates a crust/surface hoar combo, which formed in January, should remain on our radar. Due to the persistent nature of these crystals, I would expect ongoing reactivity with the potential for large avalanches.

Choose conservative lines and watch for clues of instability.>Make observations and assess conditions continually as you travel.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Storm Slabs

A storm on Monday night has built new storm slabs. In recent days, avalanches have failed within the storm snow, and "stepped-down" to deeper layers resulting in surprisingly large avalanches. Use increased caution in wind-affected terrain.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

In recent days, heavy loading from wind, snow and/or rain has triggered deep persistent weaknesses. Large destructive avalanches remain a concern, and may reach the end of their run-outs.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Jan 28th, 2015 2:00PM