Avalanche Forecast

Issued: Feb 1st, 2015 8:21AM

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

jlammers, Avalanche Canada

Northwest Coastal.

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

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Monday

Weather Forecast

Another pacific frontal system will bring snowfall to the coast on Monday. Lingering flurries are expected on Tuesday before a weak dry ridge of high pressure builds on Wednesday. Sunday night and Monday: Up to 20cm of snow / Strong southwest winds / Freezing level at valley bottom Tuesday: Very light snowfall and broken cloud / Moderate southwest winds / Freezing level at valley bottom Wednesday: Broken cloud / Moderate 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 night and Monday 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 night and Monday will build new storms slabs. Watch for increased triggering in wind-exposed terrain.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>Be alert to conditions that change with elevation.>

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 with the potential for large avalanches. Although less likely to trigger, these persistent weak layers may "wake-up" in response to a large trigger such as a cornice fall.

Be aware of the potential for large, deep avalanches due to the presence of buried crusts and/or surface hoar.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Feb 2nd, 2015 2:00PM