Avalanche Forecast

Archived

Mar 19th, 2023–Mar 20th, 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.

Skiers had a close call near Mt Birdwood on Saturday on a sun exposed slope. Check out the MIN for more details. The March sun packs a punch and can start to destabilize the snow in as little as 30 minutes.

Confidence

Moderate

Avalanche Summary

On Saturday skiers triggered a size 2.5/3 avalanche on a sun exposed slope near Mt Birdwood. This avalanche failed as the third skier crossed the slope and was triggered before the sun crust had started to break down. The slab was 30 to 80cm deep, failing on facets. Further details can be found on the MIN.

Snowpack Summary

The fresh snow from last week has largely escaped the wind.....so far. Many areas still have soft snow, but expect sun crusts on solar aspects at all elevations where the terrain is steeper than about 20 degrees. The strong late March sun is melting these surface crusts and destabilizing the slopes (see the Avalanche Summary for a close call on Saturday). There are previously formed wind slabs in alpine areas, so keep an eye out for these in lee and cross-loaded features. The midpack remains highly variable with areas of more than 100cm of total snowpack being supportive, but in shallower areas ski penetration can still be to ground. The good old facets and depth hoar still lurk at the bottom of the snowpack and present an ongoing concern for full-depth avalanches.

Weather Summary

Monday will bring a mix of sun and cloud, with the possibility of very light flurries at some point during the day. Freezing levels will rise to 2000m with ridgetop temps near -3C with light NE winds.

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.
Minimize exposure to sun-exposed slopes when the solar radiation is strong.

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.