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Avalanche Forecast

Archived

Feb 7th, 2016–Feb 8th, 2016

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

Regions

Little Yoho.

Evidence of a widespread avalanche cycle in the Yoho Valley today. Windslabs remain very touchy. Stick to low angle moderate terrain and move through the mountains conservatively for a few days yet.

Weather Forecast

A warming trend will influence the forecast region starting mid week. It is unknown at this point as to how much the trend will affect the snowpack. Until then expect continued moderate to strong at high elevations with little to no precipitation.

Snowpack Summary

Wind slabs exist in the alpine and at tree line that are easy to trigger. The Jan 6 surface hoar/facet/sun crust layer, down 40-100cm, is becoming less reactive to skier triggering, however sudden collapse results persist on the Jan 6 and Dec 3 layers. Isolated whumphing on mid-pack facets/surface hoar have been observed this past week.

Avalanche Summary

A major avalanche cycle occured on Saturday (Feb 6). Many slabs up to size 2.5 were observed throughout the Yoho Valley today. Cornices appear to be fragile due to the strong wind yesterday.

Confidence

Timing or intensity of solar radiation is uncertain on Wednesday

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.