Avalanche Forecast

Issued: Jan 31st, 2015 8:33AM

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

jlammers, Avalanche Canada

Northwest Inland.

As snow accumulates on Sunday, the Avalanche Danger will rise. Expect reactive new storm slabs to form.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

A series of pacific frontal systems will bring continued snowfall to the region. Sunday: Up to 20cm of new snow / Moderate to strong southwest winds / Freezing level at valley bottom Sunday night and Monday: Up to 10cm of snow / Moderate to strong southwest winds / Freezing level at valley bottom Monday: Up to 10cm of snow / Moderate to strong southwest winds / Freezing level at valley bottom

Avalanche Summary

Several storm slabs to size 2.5 were reported in the wake of Thursday night's storm. With more snow and wind on the way on Sunday, I'd expect continued storm slab activity. It's important to keep in mind, a surface avalanche in motion may be what it takes to trigger deeper, more destructive persistent slab avalanches.

Snowpack Summary

Prior to the weekend, moderate to heavy snowfall and strong southwest winds built deep storm slabs which are expected to be most reactive in wind-exposed terrain. Below treeline, these recent accumulations may overlie a hard, frozen crust. About 70cm below the surface, you'll likely find a rain crust which was buried on January 26. Limited observations suggest the overlying slab may have a reasonable bond at this interface.A rain crust and/or surface hoar layer buried mid-January may be found at variable depths (in some areas over 100cm below the surface). This layer is likely gaining strength, although I would keep it on my radar as it was the culprit in much of the recent destructive avalanche activity.Near the base of the snowpack is a crust-facet combination buried in November. This deep persistent weakness was also recently reactive, and may still be touchy in the far north of the region. Wherever you are, I'd be cautious of this deep and destructive layer. Possible triggers include thin spot triggering in high elevation terrain or a cornice fall.

Problems

Storm Slabs

Snowfall and wind on Sunday will build new storms slabs. Watch for increased triggering in wind-exposed terrain.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be cautious as you transition into wind affected terrain.>The new snow may require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

In the mid snowpack there are a few crusts which may be reactive to the weight of a skier. Although less likely to trigger, these persistent weak layers may "wake-up" in response to continued storm loading.

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 and/or crusts.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Deep Persistent Slabs

Although less likely to trigger, recent avalanche activity suggests weak layers buried at the beginning of the winter should still be our radar, especially in the north of the region. Avalanches at this interface may reach their run-out zones.

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.>Avoid convexities or areas with a thin or variable snowpack, especially in the north of the region.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Feb 1st, 2015 2:00PM