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Avalanche Forecast

Archived

Dec 24th, 2020–Dec 25th, 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, human triggered possible.

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.

Merry Christmas!

Weather Forecast

Friday will be sunny with an alpine inversion and moderate to strong southwest alpine winds. Alpine temperatures will be in the -5 to -10 range whereas the valleys will stay colder. Saturday and Sunday we'll see light winds, light snow and temperatures in the -5 to -15 range.

Snowpack Summary

Winds from a variety of directions have blown the ~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. Height of snow at tree line is 80-150cm.

Avalanche Summary

Avalanche control this week produced mixed results from no result to size 3. Most were storm slabs, sometimes stepping down to persistent layers. No new natural avalanches reported or observed in Little Yoho on Thursday.  See the MIN for results of avalanche control with explosives on Mt Dennis on Thursday.

Confidence

Due to the number of field observations

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.