Avalanche Forecast

Archived

Jan 28th, 2023–Jan 29th, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

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 possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Pine Pass.

There is a lot of uncertainty with the reactivity of deeply buried weak layers. Conditions like this are best managed by sticking to lower-angle terrain away from any overhead hazard.

Read more in the latest Forecaster Blog.

Confidence

Moderate

Avalanche Summary

A Thursday report identified a size 2.5 avalanche on a northeast slope, triggered by a cornice failure.

An ongoing concern for step-down and large natural and human-triggered deep persistent slab avalanches is at the forefront of our minds. Check out this video on incremental loading to learn more.

Please continue to send in your observations through the MIN.

Snowpack Summary

Wind at upper elevations continues to impact flurries and older snow, 5 cm recent flurries covers a crust up to 1600 m. Snowpack depths are shallower than normal, and several buried weak layers have been a concern over the past few weeks. Surface hoar or crust layers in the mid-snowpack may exist in this region, but field observations suggest these mid-snowpack weaknesses are less prominent here than in areas further south.

The most concerning layer in this area is at the base of the snowpack. Large, weak facets buried in November are widespread. This layer is most likely problematic in steep, rocky alpine terrain, where shallower wind slab avalanches can scrub down to these basal facets.

Weather Summary

Saturday night

Clear and with gusty ridgetop winds. Ridge wind northwest reaching 50 km/hr. Alpine temperature -26 C.

Sunday

Sunny in the morning with increasing clouds throughout the day. Ridge wind northwest 20-40 km/hr. Alpine temperature -20 C.

Monday

Increasing cloud. Ridge wind west 30-50 km/hr. Alpine temperature -18 C.

Tuesday

Flurries, 5 cm. Ridge wind northwest 30-40 km/hr. Alpine temperatures rising to -14 C.

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.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Uncertainty is best managed through conservative terrain choices at this time.

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.