Avalanche Forecast

Archived

Mar 19th, 2023–Mar 20th, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

North Rockies, Kakwa, McGregor, Pine Pass, Tumbler.

Lingering wind slabs may remain reactive to human triggers in isolated locations at upper elevations.

Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

Confidence

Moderate

Avalanche Summary

Numerous size 1 wet loose avalanches triggered by solar radiation were reported on sunny aspects below treeline on Saturday.

Snowpack Summary

Expect to find a melt-freeze crust on the surface of all aspects at treeline and below and on sunny aspects in the alpine. Solar radiation will break down the crust on sunny slopes throughout the day.

Lingering wind slabs may remain reactive to human triggers in isolated locations at upper elevations.

The middle of the snowpack is generally well-settled and strong.

A weak layer of large facets is found near the base of the snowpack. This layer is of most significant concern in shallow snowpack areas in the north and east of the region. The most likely areas to trigger this layer are shallow, rocky areas or where the snowpack transitions from thin to thick.

Weather Summary

Sunday Night

Clear skies / 40 km/h east ridgetop wind / Temperature at treeline around -8 C / Freezing level valley bottom

Monday

Sunny / 30 km/h east ridgetop wind / Temperature at treeline around -2 C / Freezing level 1700 m

Tuesday

Sunny / 20 km/h northwest ridgetop wind / Temperature at treeline around -1 C / Freezing level 1800 m

Wednesday

Mix of sun and cloud / 40 km/h west ridgetop wind / Temperature at treeline around -4 C / Freezing level 1500 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Minimize exposure to sun-exposed slopes when the solar radiation is strong.
A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
Cornice failure may trigger large avalanches.
Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

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.