Avalanche Forecast

Issued: Jan 31st, 2015 8:42AM

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

jlammers, Avalanche Canada

Northwest Coastal.

As new snow accumulates on Sunday, the Avalanche Danger will rise. Expect changing conditions throughout the day.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

A series of pacific frontal systems will bring continued snowfall to the region. Sunday: Up to 25cm of new snow / Moderate to strong southwest winds / Freezing level at about 500m Sunday night and Monday: Up to 20cm of snow / Moderate to strong southwest winds / Freezing level at about 500m Monday: Up to 20cm 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. More snow and wind forecast for Sunday will add to this ongoing storm slab problem.About 100cm 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 up to 150cm below the surface). This layer is likely gaining strength, although I would keep it on my radar especially at higher elevations as it was the culprit in much of the recent destructive avalanche activity.The November crust/ facet combo near the bottom of the snowpack is thought to be generally well bonded. However, this deep and destructive layer is still reported to be reactive in the far north of the region.

Problems

Storm Slabs

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

Be cautious as you transition into wind affected terrain.>Good day to make conservative terrain choices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

In the mid snowpack there are a few crusts which may be reactive to the weight of a skier in steep high elevation terrain. Although less likely to trigger, these destructive weak layers may "wake-up" with continued heavy storm loading.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Be aware of the potential for large, deep avalanches due to the presence of buried crusts and/or surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

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