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Avalanche Forecast

Archived

Feb 23rd, 2018–Feb 24th, 2018

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

Regions

Cariboos.

New snow (possibly up to 20 cm by Sunday) and wind will continue to build slabs and cornices at upper elevations. Sloughing, and cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

TONIGHT: Light flurries. Accumulation up to 5 cm. Ridge wind moderate to strong, west. Temperature -16. Freezing level valley bottom.SATURDAY: Mainly cloudy, light flurries increasing overnight. Accumulation up to 5 cm. Ridge wind moderate, southwest. Temperature -8. Freezing level valley bottom.SUNDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind moderate to strong, west. Temperature -8. Freezing level valley bottom. MONDAY: Cloudy, flurries. Accumulation trace. Ridge wind moderate to strong, southwest. Temperature -6. Freezing level valley bottom.

Avalanche Summary

On Wednesday a size 2, natural cornice release was reported on a southeast aspect at 1900 m in the northern part of the region.Tuesday there was a report of a skier triggered size 1.5 soft, wind slab release (25-50 cm deep) on a northeast-facing open, treeline slope at 1900 m.Last weekend (Feb 17 & 18),natural wind slab activity to size 3 was reported on south / east aspects from 1250m right up to 2400m elevation, as well as reports of a large avalanche running on a deeply buried weak layer with 1.5m crown and good propagation on east-facing, steep open terrain below treeline. See this MIN post for a good example of these avalanches. Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.

Snowpack Summary

A light dusting of new snow on Friday now covers 20-40cm of storm snow from last week that has been redistributed by previously strong winds creating reactive hard wind slabs in open areas on downwind features. These accumulations overlie an interface that was buried mid-February and consists of; a mix of older wind slabs in exposed higher elevation terrain, a sun crust on steep solar aspects, and surface hoar on sheltered slopes.Below the snow surface, several persistent weak layers make up a complex snowpack that is starting to show signs of improving but still remains suspect. In the top 100-150 cm of the snowpack, two surface hoar layers buried in January can be found. Expect to find at least one of these layers on all aspects and elevations.Deeper in the snowpack (150-200 cm deep) is a facet/crust/surface hoar layer from December that is most prevalent at treeline and below.Near the base of the snowpack is a crust/facet combo from late November.

Problems

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.

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.