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Avalanche Forecast

Archived

Apr 3rd, 2015–Apr 4th, 2015

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

Regions

Northwest Coastal.

A weak layer of surface hoar and facets has created touchy avalanche conditions in parts of the region. If you have field observations, please consider sharing them through the Mountain Information Network

Confidence

Good - Forecast snowfall amounts are uncertain

Weather Forecast

5-10cm of snow is expected throughout the day Friday with another 5 cm each day on Saturday and Sunday. Daytime high freezing levels are expected to hover around 1300 m for Friday and Saturday and a bit higher on Sunday. Alpine winds are expected to belight throughout the weekend.

Avalanche Summary

There have been several explosive-controlled wind slab avalanches up to Size 2.5 running on facets buried March 25th. On Thursday, a remotely triggered Size 2.5 avalanche released above two skiers catching both of them and burying one, who was successfully recovered. This avalanche failed on the same March 25th weakness, where it was buried surface hoar on a northeast aspect at 1450 m.

Snowpack Summary

50-70 cm of recent settled storm snow is bonding poorly to a variety of old snow surfaces including surface hoar and facets buried on March 25th. This weakness is very touchy with a high propensity for propagating fractures, especially where buried surface hoar exists. The problem seems more touchy in the northern part of the region, but has been reported throughout the northwest coastal area. Weaknesses have also been found within the recent storm snow with snowpack tests producing moderate sudden results down approximately 30 and 40 cm. The early March facet/crust persistent weakness is now down around a metre and appears unreactive with snowpack tests.

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.

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.