Avalanche Forecast

Archived

Jan 20th, 2024–Jan 21st, 2024

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

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Things have changed, and temperatures have warmed up!

With warming comes the potential for increased sensitivity to triggering.

Watch for newly formed wind slabs and the potential for initiating the deep persistent problem in thin to thick areas.

Confidence

Moderate

Avalanche Summary

Lake Louise reported a couple of size 2 explosive results on wind slab stepping down to the ground on Jan 20.

On Jan 19 Sunshine reported explosive results on the basal facets up to size 3 specifically on an alpine southerly facing feature called Jaws (out of bounds)

Additionally, wind slabs have been reactive to skier traffic and explosives up to size 2.

Within the last 24-72h there have also been several avalanches out of extreme terrain to size 1.5, loose dry and wind slabs.

Snowpack Summary

10-20 cm of recent snow has formed windslab and widespread wind effect in the alpine and exposed areas at treeline. 30-50 cm overlies the Dec. 31 surface hoar/sun crust. Below this, in the mid-pack, two crusts (Dec. 22 and Dec. 5) exist as high as 2350m and have been providing the primary support for skiing. The base of the snowpack remains weak with depth hoar and facets.

Banff Visitor Safety dug a snow profile around Sunshine Ski Hill (Jan 19) for more details.

Weather Summary

Sat night: M winds from the southwest will continue overnight with alp temp lows of -8 . Up to 5cm of precip.

Sun: L to M winds from the southwest with alp temps around -8. Cloudy with scattered flurries of trace amounts of snow.

Mon-Tues: Cloudy with 30 percent chance of flurries. Temps just below freezing at TL. Trace amounts of snow with light winds from the SW

For more information, click here for the Mountain Wx Fx.

Terrain and Travel Advice

If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.