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Avalanche Forecast

Archived

Jan 5th, 2021–Jan 6th, 2021

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

Regions

Jasper.

Strong SW winds continue to build wind slabs tree line and above.  Although natural avalanche activity has decreased, conservative terrain selection is still advised.

Weather Forecast

Wednesday will see flurries with up to 10cm accumulating.  Ridge top winds will remain moderate to strong from the southwest.  Freezing level will remain at valley bottom high near -7.

Thursday mix of sun and cloud with no precipitation expected.  Winds will become light; high near -9.

Snowpack Summary

Up to 45cm of new snow this past weekend is being redistributed by strong SW winds. This new snow has further buried the mid-Dec persistent layers (surface hoar and facet combo) down 40-70cm. The mid-pack is supportive where snow is deeper than 60cm. The bottom of the snowpack consists of facets and depth hoar.

Avalanche Summary

Serval large natural avalanches were observed over the weekend in the alpine on all aspects. Avalanche control had varied results from no results to several size 3 wind slabs stepping down to deep weakness on all aspects in the alpine.

No new naturals observed today Hilda area.

Make your field trip observations count! Mountain Information Network.

Confidence

Wind effect is extremely variable

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.