Avalanche Forecast

Archived

Apr 13th, 2023–Apr 14th, 2023

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

Kananaskis, Bow Valley, Highwood Pass, North 40, Spray - KLakes.

Big temperature swings are the norm these days. Expect a rapid decrease in stability/increase in hazard as the sun comes out, or if air temperatures increase.

Confidence

Moderate

Avalanche Summary

The natural cycle continued today, although its hard to figure out what's new and what's old. A sz2.5 solar triggered avalanche was witnessed today on a steep alpine slope.

Snowpack Summary

Cooler temperatures have helped stabilize the snowpack where previously it lacked structure and was rain soaked. This is mainly below 2200m or just below treeline. Above this elevation the snow was drier and windslabs formed with the strong SW flow. These windslabs are overlying a variety of different surfaces from crusts on solar aspects to dry snow on more polar. Carefully evaluate this bond as you travel. A deeper persistent layer down 1m was active in many avalanches over the past few days. This layer was most active on N and E aspects. Treat any area that have not slid as suspect and requires careful evaluation or imply avoidance. Deeper in the snowpack the weak facets and depth hoar at the base of the snowpack is still there. As temps warm up and this layer begins to settle and squish out it will improve and begin to bond but for now, its still a layer to think about as you travel. Thin areas is where you may be able to trigger this weakness.

Weather Summary

Tomorrow will start with mostly clear skies, but by mid morning clouds will build. An overnight low of about -13 is expected with a rise in temperatures later in the morning. The high will be -3, but with the sun factored in low elevation areas will be above zero by noon. Convective flurries will appear in the afternoon, giving a modest 2cm. Winds will be light from the SW. Freezing level 2100m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.