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Avalanche Forecast

Archived

Jan 20th, 2016–Jan 21st, 2016

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

South Coast.

Conditions are ripe for an impressive avalanche cycle. Thursday is a day to wait out the storm from a safe place.

Confidence

High

Weather Forecast

Tonight and Thursday: 30-50 cm of snow. The freezing level starts near 1000 m and rises to 1600-2000 m late in the day. Winds are strong from the South. Friday: A few flurries and a clearing trend. The freezing level dips slightly to 1500 m. Winds ease to light from the SW. Saturday: Cloudy with sunny breaks. The freezing level is around 1200 m and winds remain light from the W-SW.

Avalanche Summary

A fairly widespread natural avalanche cycle was reported below treeline on Tuesday. Numerous slab avalanches up to size 2 were observed, primarily on sun affected slopes. On Tuesday there was also an incident on Mount Chief Pascal. One person was partially buried after triggered a 60-80 cm deep slab on North aspect near treeline. Check the Mountain Information Network for photos and more information on this incident. Conditions are primed for a large and widespread natural avalanche cycle with the incoming storm on Thursday.

Snowpack Summary

30-40cm of fresh storm snow has buried the recently formed mid-January surface hoar layer. Below that are the two early-January interfaces down 50-80cm which are separated by around 5-10cm of snow and both consist of a sun crust on steep solar aspects and a layer of surface hoar on sheltered and shady slopes. Strong southeast through southwest winds have been loading lee features at treeline and in the alpine. The mid and lower snowpack is generally strong, with the exception of shallow snowpack areas that may be more faceted.

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.