Avalanche Forecast

Issued: Feb 26th, 2014 8:20AM

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

bcorrigan, Avalanche Canada

Cariboos.

The hazard may increase with rising temperatures and solar warming on South aspects. See the forecasters blog for more information on current tricky conditions.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The arctic ridge of high pressure dominates conditions for the forecast period. Clear and dry conditions with cold arctic air scheduled to move back into the region. Strong arctic outflow winds have already begun and will continue into the coming weekend.Wednesday night: freezing level at valley bottom, ridge top winds light-variable.Thursday: Sunny with some cloudy periods, freezing level around 1400m, ridge top winds, light to 25Km/h.Friday: Sunny, freezing level at valley bottom, ridge top winds from the north to 20 Km/hSaturday: Freezing level at valley bottom, light ridge top winds from the north.

Avalanche Summary

We're still receiving reports of large natural avalanche activity in the forecast region. One operator has reported evidence of a recent avalanche cycle in steep terrain with avalanches up to size 2.5. Solar warming on steep south aspects may trigger avalanches that might "step down" to weak mid -pack and basal layers possibly triggering a very large slide. Conditions are ideal for human triggering right now. We have received numerous reports of skier triggered avalanches in the last few days, many of which have released quite deep in the snowpack. Several cornice failure avalanches have been reported.

Snowpack Summary

A dense slab with an average thickness of 1.5 metre sits on a nasty persistent weak layer (surface hoar/facet/crust combo) that was formed during the preceding month of cold, dry weather. This weak layer is widespread at all elevations and aspects, and is reactive even in previously skied terrain. Large settlements and whumpfs have been reported at all elevations. We have received numerous reports of remotely-triggered avalanches indicating the ability of this weak layer to fail and propagate over large distances. Touchy conditions are expected to remain in place longer than we're normally accustomed to. Some Katabatic (down-flowing) winds slab formation is being reported as well.Recent strong winds out of the SW through NW have created wind slabs on lee features in wind exposed areas at tree line and above. In many wind loaded areas, a slab of up to 2 m thickness overlies the persistent weak layer creating conditions for very large avalanches.Weak basal facets exist in some areas, but triggering has now become unlikely. For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

Persistent Slabs

A thick storm slab from the last series of storms now lies above a touchy, persistent weak layer. This slab has shown a propensity for remote triggering and propagating over wide distances. In wind-loaded areas the slab may be up to 2m thick.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Use very conservative route selection, stick to simple well supported terrain that is low consequence and free of overhead hazard.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Wind Slabs

Previous storm winds have created wind slabs on lee terrain features. The primary wind direction was SW but we also had some NW winds. Weak cornices are also a concern and have the potential to trigger large avalanches on the slopes below.

Avoid freshly wind loaded features.>Travel on ridgetops to avoid wind slabs on slopes below.>Do not travel on slopes that are exposed to cornices overhead.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Feb 27th, 2014 2:00PM