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Avalanche Forecast

Archived

Jan 28th, 2018–Jan 29th, 2018

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Cariboos.

Warm storm coming! A widespread avalanche cycle is expected so it's best to avoid all avalanche terrain.

Confidence

Moderate - Track of incoming weather systems is uncertain

Weather Forecast

Monday: 10-20 cm snow Sunday overnight into Monday and another 10-15 cm snow during the day. Moderate to strong south-westerly winds. Alpine temperature warming to near -3. Freezing level rising to 1500m by late afternoon.Tuesday: Light snow (5cm possible). Light to moderate southerly winds. Alpine temperature -4. Wednesday: Cloudy with isolated flurries. Light westerly winds. Alpine temperature near -5.More information can be found in the Mountain Weather Forecast.

Avalanche Summary

Widespread recent avalanche activity was reported on Saturday near Allen Creek. Avalanches from Size 1 to 3 (many triggered by humans) were observed, especially on north east aspects between 1900m and 2600m. See this great MIN report for more information. A widespread natural avalanche cycle is expected with Monday's storm, with the potential for some surprisingly large avalanches given how many persistent weak layers exist in the snowpack.

Snowpack Summary

The current snowpack is complex, with three active weak layers that professionals are monitoring. Recent storm snow has been blown around by winds to form wind slabs and cornices.1) Down about 30-70 cm is a crust and/or surface hoar layer buried mid-January. The surface hoar is up to 10 mm in size, found at all elevation bands and very reactive on north east aspects between 1900-2600m.2) Deeper in the snowpack, the early-January persistent weak layer is found 40 to 120 cm below the surface. It is composed of surface hoar on sheltered slopes and sun crust on steep solar aspects and found at all elevation bands. Snowpack tests show sudden fracture characters with easy to moderate loads and high propagation potential. 3) Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 100 to 160 cm deep. It is most problematic at and below tree line.A rain crust buried in November is 100 to 200 cm deep and is likely dormant for the time being.See here for a good summary of snowpack test results.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.