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Avalanche Forecast

Archived

Dec 25th, 2020–Dec 26th, 2020

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

Regions

Little Yoho.

http://www.pc.gc.ca/apps/links/goto_e.asp?destination=http://avalanche.ca/spaw/2020-12-23-spaw

It's a tricky snowpack in many parts of the forecast region with a lot of variability with recent winds, snowfall and multiple weak layers.

There is a Special Avalanche Warning in effect. Click Here to access.

Happy Holidays!

Weather Forecast

Saturday will be cloudy with snow accumulations between 2-10cm over the region. The temperature inversion will dissipate as temps gradually get cooler over the next few days, ranging from -8 to -14. Winds will taper off Friday evening and remain light through the weekend. Cool temps, light winds and no snow in the 5 day forecast.

Snowpack Summary

Recent 25-45km/hr SW-W winds have blown the 30-60cm of snow from the past week into wind slabs at higher elevations. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 50cm and ~80 cm respectively. The decomposing Nov crust/facets sits at the bottom of the snowpack. Height of snow at tree line is 120-170cm.

Avalanche Summary

Avalanche control this week produced mixed results, from no result to size 3.0. Control on Mt. Dennis on Thursday produced numerous size 2.0 avalanches, initiating in pockets of alpine wind slab and entraining additional snow in the tight gullies below, see MIN. These results are easily produced due to the steep and tight nature of the terrain.

Confidence

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.