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Avalanche Forecast

Archived

Mar 20th, 2017–Mar 21st, 2017

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

Regions

South Coast Inland.

Although avalanche danger levels remain constant a short lived spike in the freezing level on Tuesday into Wednesday may make deeper buried weak layers more reactive in the alpine and tree line elevations. A cautious approach is recommended.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

TUESDAY: Periods of rain showers or snow flurries, accumulation 5-10cm / Light to moderate south wind / Alpine temperature 1 / Freezing level 2000m WEDNESDAY: Flurries / Light to moderate southwest wind / Alpine temperature -3 / Freezing level 1400mTHURSDAY: Mix of sun and cloud and possible isolated flurries / Light to moderate south wind / Alpine temperature -3 / Freezing level 1300m

Avalanche Summary

There is no recent avalanche activity to report. That being said through last weekend there were numerous natural and explosives controlled avalanches reported to size 3 that were triggered in the storm snow and stepped down to one of the February weak layers. On Friday, a large cornice fall missed a group of skiers on a north aspect in the Duffey area. Click here to See a MIN report for details. On Tuesday, wind slabs may remain reactive in human triggers at upper elevation. In northern parts of the region, the deeper February weak layers continue to present a low probability / high consequence scenario.

Snowpack Summary

Expect another 5-10cm of snow at upper elevations to add to the storm snow amounts from last weekend which totalled roughly 40 cm around Coquihalla and Allison Pass and 30 cm around Duffey Lakes. Freezing levels reached roughly 1400 m at that time, resulting in rain and/or wet snow at lower elevations. Thicker wind slabs and large cornices likely exist in alpine terrain. The storm snow sits above a widespread rain crust up to about 2100 m, but the snow will likely form a good bond to this crust. In the north of the region, the February weak layers are 80-120 cm deep and include a buried surface hoar layer that recently produced a few persistent slab avalanches and a crust/facet layer that appears to be gaining strength. In the southern parts of the region, the lower snowpack is generally stable.

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.