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Avalanche Forecast

Archived

Jan 26th, 2019–Jan 27th, 2019

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Cariboos.

Fresh wind slab formation is expected Sunday in the alpine, but our main concern is still the surface hoar down 15 to 40 cm which is most prevalent between 1500 and 1800 m, this interface likely remains sensitive to human triggering.

Confidence

Moderate -

Weather Forecast

Sunday marks the start of a pronounced ridge of high pressure that is expected to be with us through at least Tuesday. This period is marked by clearer skies, cooler temperatures and a lack of precipitation.SATURDAY NIGHT: Freezing level returning to valley bottom overnight, strong to extreme west wind, 2 to 10 cm of snow possible.SUNDAY: Scattered cloud cover initially, clearing in the afternoon, freezing level at valley bottom, moderate to strong northwest wind, trace of snow possible.MONDAY: Mostly clear skies in the morning with cloud cover increasing throughout the day, freezing level at valley bottom, light northwest wind, no precipitation expected.TUESDAY: Clear skies, freezing level at valley bottom, light variable wind, no precipitation expected.

Avalanche Summary

On Friday numerous small wind slabs 15 to 20 cm in depth were observed on small north facing rolls around 2000 m.  There was also a report of a natural avalanche underneath a large cornice, photos here. A few natural wind slabs, storm slabs and dry loose avalanches up to size 2.5 were reported on Wednesday and Thursday on steep slopes on a variety of aspects at treeline and alpine elevations.

Snowpack Summary

15 to 40 cm of snow sits above a layer of large surface hoar crystals and sun crust. In areas that have had wind effect the recent snow has been settling into a thin but reactive slab above this weak layer, with enhanced reactivity noted at elevations between 1500 and 1800 m. In sheltered areas the snow is faceting and lacks cohesion above this layer which is only reactive as dry loose sluffing. Slightly warmer temperatures are starting to consolidate the upper snowpack which will likely make slab avalanches more sensitive to human triggering. The middle and lower portions of the snowpack are generally well-settled and strong.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.