Avalanche Forecast

Issued: Mar 5th, 2014 8:53AM

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 jlammers, Avalanche Canada

Recent and forecast snowfall amounts are highly variable throughout the region. Posted danger ratings are best aligned with conditions along the western boundary of the region.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Wednesday night: 5-15cm of new snow / Strong southwest winds / Freezing level at about 900mThursday: 10-15cm of snow / Moderate southwest winds / Freezing level at about 1500mFriday: Light snowfall / Moderate to strong southwest winds / Freezing level at about 1500mSaturday: 10-15cm of snow / Moderate to strong southwest winds / Freezing level 1600-2000m

Avalanche Summary

Although observations were limited on Tuesday, several storm slabs to size 1.5 were observed on all aspects in alpine terrain. In recent days, 3 persistent slab avalanches in the 2-2.5 range were triggered naturally or remotely close to Invermere. Over the past week in the Dogtooth Range skiers initiated a cornice fall which triggered a size 2.5 slab avalanche on the slope below. In the same area a size 2 slab was rider triggered from a ridge crest. The February 10th interface was the culprit in these events.I expect avalanches to increase in size and frequency with forecast weather.

Snowpack Summary

Although snowfall amounts have been highly variable throughout the region, in some deeper snowpack areas over 80cm of storm snow overlies weak surface hoar in sheltered areas, a sun crust on solar aspects and wind slabs in exposed terrain. On lee slopes these accumulations have been pushed into much deeper deposits by generally moderate southwest winds. Ongoing snowfall, wind and warming will add to the reactivity and destructive potential of this developing storm slab.There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 60 and 150cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. In some areas destructive avalanches are still a real concern with recent reports of natural triggering, whumpfing and sudden/easy snowpack test results. The mid and lower snowpack are generally strong and well consolidated. Weak basal facets exist in many areas, but triggering has now become unlikely.

Problems

Storm Slabs

An icon showing Storm Slabs
Ongoing snowfall, wind and warming have added to the reactivity and destructive potential of a punchy storm slab which overlies a number of potentially weak layers. In many areas conservative terrain selection has become critical.
Be alert to conditions that change with elevation.>Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Ongoing persistent avalanche activity proves layers formed about a month ago deserve respect and should still be in the front of your mind. See the Avalanche Summary in the Forecast Details section for more info on recent activity at this interface.
Avoid areas with overhead hazard.>Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Mar 6th, 2014 2:00PM