Avalanche Forecast

Archived

Mar 17th, 2023–Mar 18th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

Pay attention as you climb into Treeline and Alpine areas for the presence of windslabs in the upper snowpack. The sun is packing a punch these days so keep overhead terrain and aspect in your mind as you travel. As it warms up stability will decrease on these aspects.

Confidence

Moderate

Avalanche Summary

Forecaster were out of the field by 1400 and had observed no new avalanche activity by this time. It would seem the more widespread natural avalanche cycle is beginning to taper.

Snowpack Summary

Recent storm snow has settled into a pleasant 20cm of settled snow. So far the winds haven't made an appearance which means we've been spared a widespread wind slab problem. There are some wind slabs still lurking in the alpine, but they generally seem to be high and in steep alpine terrain. But there is a catch (when isn't there?), the March 12th crust (solar) or facet (polar) layer is a slippery one and it doesn't need much of a cohesive surface layer to pose a problem. Unsupported alpine and treeline terrain is still concerning. The mid to lower pack remains variable, in every sense of the word. The depth changes dramatically on elevation, and the supportiveness of it seems to change at the drop of a hat. Thin spots and rocky areas are still a likely place to trigger the deeper problem layers.

Weather Summary

The high pressure ridge overhead is forecast to continue into Saturday. Temperatures will start at -18 and rise to -3 by early afternoon with a freezing level forecast to be around 2000m. The solar input was noticeable today, expect the same strong inputs on Saturday. As for the wind, only light breezes are expected for the next few days. Beautiful touring at the moment out there!

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Cornices become weak with daytime heating or solar exposure.

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.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.