Avalanche Forecast

Issued: Feb 24th, 2014 8:49AM

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.

Avalanche Canada bcorrigan, Avalanche Canada

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

A strong arctic ridge of high pressure dominates conditions for the forecast period. Clear and dry conditions are expected for the next three days with a bit of a warming trend.Monday night: Clear and cold, treeline temperature around -10C, ridgetop winds light NETuesday: Clear and sunny, treeline temperature around -7C, ridgetop winds light variableWednesday: Clear and sunny, treeline temperature around -6, possibility of an alpine temperature inversion - ridgetop winds light variableThursday: Sunny with some cloudy periods, some flurries with a possibility of an alpine temperature inversion, light ridge top winds.

Avalanche Summary

We have been receiving less reports of natural activity in the last couple days, but the natural avalanches that have occurred have been increasing in size. Neighbouring regions reported natural activity up to size 2.5. Conditions are ideal for human triggering right now and we have received numerous reports of skier triggered avalanches, many of which have released quite deep in the snowpack. Several of these avalanches were remotely triggered.On Sunday operations were getting widespread explosive triggered results. The farthest ran 600km and the was 200m wide with a crown of 150cm. That particular slope had run earlier in the season on the basal face layer and since re-loaded..On Monday, two, size 2 skier accidentals  were reported with one of them 40m wide, having a fracture line of 60cm that ran for 250m.

Snowpack Summary

A cohesive slab with an average thickness of 1m 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 creating problems even in previously skied terrain. Large settlements and whumpfs have been reported at all elevations. We have received numerous reports of remotely-triggered avalanches from as far as 500m away which indicates a high likelihood of large propagation within the weak layer. Touchy conditions are expected to remain in place longer than we're normally accustomed to. Recent strong winds out of the SW through NW have created wind slabs on lee features in wind exposed areas at treeline 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 and depth hoar have been noted in reports from 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

An icon showing Persistent Slabs
A thick slab from February storms sits on top of a touchy persistent weak layer. This slab has shown a propensity for remote triggering and large propagation. 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

An icon showing 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. Cornices are also a concern and have the potential to trigger large avalanches on the slopes below.
Avoid freshly wind loaded features.>Minimize overhead exposure; avalanches triggered by windloading may reach run out zones.>Travel on ridgetops to avoid wind slabs on slopes below.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Feb 25th, 2014 2:00PM

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